Author Topic: 8116A Code 42  (Read 32535 times)

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Offline Mick BTopic starter

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8116A Code 42
« on: January 18, 2024, 09:05:42 pm »
Hello all, Quick catch-up. This was given to me because a screwdriver was dropped into it, it was working before this. It had multiple issues & killed the -24V rail. I replaced the Shaper output amp transistors Q505 ~ Q513 (except Q507) and a couple of emitter resistors. R559 & R560. The display came up now. and so did CODE-42 I started on the troubleshooter at chapter 10.4.1 as per the manual.
the first test, Input pins 18-19 I have a signal, but they are NOT 180° OUT of phase, but ARE IN PHASE. TP4 looks ok. At this point
I got sidetracked by Q502 being too hot to touch. (only this transistor) the others aren't even warm. Testing output transistors
Q501 ~ Q513 (except Q507) when testing PNPs, Q511 & Q513 in diode mode red lead on the emitter black in the collector to shows a cap charging and then open circuit. OK. When testing Q510 & Q512 red lead on the collector black on the emitter I see a cap charging up but never gets to open circuit.? i pulled 10 &12 they test fine caps charge up and goes to open circuit. I'M LOST.
« Last Edit: January 31, 2024, 08:37:13 pm by Mick B »
 

Offline MarkL

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Re: [HP] 8116A Code 42
« Reply #1 on: January 30, 2024, 12:03:59 am »
(So for other readers, this would be an HP 8116A function/pulse generator...)

Hello all, Quick catch-up. This was given to me because a screwdriver was dropped into it, it was working before this. It had multiple issues & killed the -24V rail. I replaced the Shaper output amp transistors Q505 ~ Q513 (except Q507) and a couple of emitter resistors. R559 & R560. The display came up now. and so did CODE-42 I started on the troubleshooter at chapter 10.4.1 as per the manual.
That's an awful lot of replacements.  Did you verify they were all faulty after being removed?

Quote
the first test, Input pins 18-19 I have a signal, but they are NOT in phase. TP4 looks ok.
So, when you say TP4 looks ok, you mean the test configuration is producing the waveform in figure 10.5-6?  And when you perform the test at amplitude 9.99V and 16.0V, TP4 is following those voltages too?  Do you have any screen shots or scope photos of what TP4 looks like?  Does the unit produce any output?

You might have to come back and address the pin 18 & 19 issue, but if TP4 is operating normally (which is the input to the output amplifier), I'd recommend working on the output amplifier section first.

Quote
At this point
I got sidetracked by Q502 being too hot to touch. (only this transistor) the others aren't even warm. Testing output transistors
Q501 ~ Q513 (except Q507) when testing PNPs, Q511 & Q513 in diode mode red lead on the emitter black in the collector to shows a cap charging and then open circuit. OK. When testing Q510 & Q512 red lead on the collector black on the emitter I see a cap charging up but never gets to open circuit.? i pulled 10 &12 they test fine caps charge up and goes to open circuit. I'M LOST.
When in diode test, your multimeter is applying a test voltage to the probes.  On a good PNP transistor, it should display a voltage of 0.6V to 0.7V, which is one diode drop, when measuring red (+) to Emitter and black (-) to Base.  You should also get a diode drop with the black (-) on the Base again, and red (+) to the Collector.  Reverse polarity in both of these positions should show open.  On NPN, the polarity for the four tests is reversed.  Try it on a known good transistor out of circuit if this isn't clear.

Note that it's not always possible to do the diode test in circuit because other components can interfere, and often do.  If there's a capacitor, as you seem to be seeing, it might take a while for the test voltage to settle to the final value.  Or there may be a lower impedance path that will prevent the diode inside the transistor from turning on and your meter will show an incorrectly low voltage.  Or the transistor could be open, but another component is conducting the test current and creating a "good" reading on the meter.  It's just not 100% reliable.  In one case however, if you get a reading of 0.0V that's usually a good sign it's shorted (but again not *always*).

So, unsoldering a transistor, testing it, and then putting it back is one way to do it.  But that is time consuming, and risks damage to the board.  A better way, if the board can be safely powered up, is to look at the various voltages around the transistor leads.  If the transistor is in an active state, you should be able to measure the 0.6V to 0.7V diode drop across the B-E pins with your voltmeter (called "bias").  Although there's a lot else that can go wrong, looking for the bias voltage is usually a good test for a first pass.

If you don't see a bias voltage, a closer look at the schematic is needed to determine if the bias voltage should be there.  A transistor might be normally off (for example, when used as a current limiter) and would not have a B-E bias voltage of 0.6V to 0.7V.

So, if Q502 and other components are not smoking hot or turning odd colors, I would power up the board for short intervals and check the voltages described on page 10.4-14.  This section is checking voltages around some of the transistors that you replaced.  Feel free to post your readings.  There might be some clues where to look next.

You can also use your meter's diode test to check the various diodes in this circuit.  Although it has the same caveats described above for in-circuit testing of transistors, if a diode is bad it's usually shorted and that will show up as 0V.

If you remove a component that you suspect was bad as a result of in-circuit testing, I'd recommend always testing it again out of circuit to confirm your diagnosis.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #2 on: January 31, 2024, 11:23:47 pm »
Hi Mark, Thanks for showing up. I put the Q510 & Q512 transistors back in They tested good out of circuit. Once again Q502 is to hot to touch. I checked TP4 as you can see at 999mV its just a blond one high and just gets nasty at 9.99V & 16V I corrected an error in my post above about pins 18 & 19 it now says pins 18 & 19 are in phase but supposed to be 180° out
I have not retested them again.
« Last Edit: April 11, 2024, 09:02:18 pm by Mick B »
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #3 on: January 31, 2024, 11:39:45 pm »
Here is the output @ 1K 1V this is sad. The output files are named output S and T and SQ = sine, tringle, square   Mark what time zone are you in?
« Last Edit: January 31, 2024, 11:41:56 pm by Mick B »
 

Offline MarkL

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Re: 8116A Code 42
« Reply #4 on: February 01, 2024, 04:14:56 pm »
Ok, so as you've noted, when the unit is set on the 999mV range TP4 looks normal, and when set higher it starts to distort.  This is because less attenuation is switched in between TP4 and the output amplifier input on the higher ranges (relays K501-K504).  As you set the unit's output range higher, there's less isolation between TP4 and the output amp, and misbehaving voltages from the output amp input are making it back to TP4 (probably).

And looking at the unit's final output, clearly it's stuck above 0V when the waveform should be more or less symmetric around 0V.  So something is wrongly dragging the output high.  Q502 is one of the intermediate drivers trying to pull the output low, so it's not a surprise it's hot.  It's probably fighting against something that's keeping the output high.

The next thing I would check is voltages around Q501 and associated circuitry.  Q501 is likely the component Q502 is fighting, since Q501 is the high side of the Q501/Q502 pair.

The suggestion of looking at the voltages described on page 10.4-14 is still valid, although perhaps we only need steps 1 to 3 at the moment.  I would further look at the voltages on EBC of both Q501 and Q502 with respect to ground.  If you post your findings, it will probably provide some clues where to look next.  If needed, we can also compare with a working 8116A I have here for voltages not listed or not apparent from the schematic.

(I'm on the east cost of the US, so EST.)
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #5 on: February 01, 2024, 11:11:38 pm »
HP8116A
Hello Mark, I am on the east cost also NC.
Initial Diagnose: All display LEDs on and stops. Found no -24V rail.
Transistors NPN Q512 is bad but not a dead short, PNP Q513 is ok,
NPN Q510 is open--- PNP Q511 is shorted.---Q508 & Q509 are ok. R559 & R560 were burnt and replaced along with all the power transistors from Q505 ~ Q513 except bias transistor Q507 was not. It tested ok. (in circuit)
The 24v rail problem is gone !
Next:
CODE 42: Diagnostics with MarkL settings @ f~1k @ 999v output on.
Testing Transistors Q501 & Q502 results Q501 =
E.- testing at R518=  0.67mV
B.- testing at CR501= 0.670V.     
C.- testing at VR501= 23.58V
results Q502 =
E.- testing at R519= -111.3mV
B.- testing at CR502= - 0.746mV
C.- testing at VR502= - 8.888V
Testing CR501 & CR502
CR501 Anode to Gnd.= 0.66V            Cathode to Gnd.=047.5mV   DROP=0.7V
CR502 “…………………” = -047.3mV        "…………………… “=-0.73V        Drop=0.69V 

Well, after doing this I retested Q503 and Q504 the diode drops are way off, as are CR503 & CR504 I’m hoping it's just because there in circuit.
 

Offline MarkL

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Re: 8116A Code 42
« Reply #6 on: February 02, 2024, 02:31:07 am »
From your measurements, it appears that Q501 is completely off.  It has near +24V on its collector, so is therefore drawing little to no current.

So, my first question is, since Q501 appears to be off, where is Q502 getting its current that's making it so hot?  And should it be on to this extent in the first place when the system output is supposed to be 0V?  I'll bet R527 is hot too.  What voltage are you seeing on R527?

What voltage are you measuring at the junction of R518 and R519?  This is the input to the output amplifier.  It should be near 0V with the unit set to the 999mV range.

It could also be helpful if you could measure the voltages across zeners VR501 and VR502.  They should be limiting the drop across the associated 2k resistor to 12.1V.  It might be on in VR502's case.

Q503 and Q504 are part of the next stage, which is a gain stage, but it may help to know what they are seeing from the Q501/Q502 pair.  It might be helpful if you could do the EBC measurements on them too.

Opamps U501 and U502 both play role in setting quiescent current of the output amp, so it might be interesting to take a look at their respective outputs (pin 6), and in the case of U501, the junction of the emitters of Q514 and Q515, which is the output from the offset current stage.

Also, note that the designers have provided a nice hint:  The heavy line in the schematic is showing you the waveform signal path from input to output, which can be helpful.

In the meantime, I will extract my 8116A so I can open it and take at some voltages too.  It's currently at the bottom of a stack of other instruments with many GPIB cables, so it's a little involved.

Also, a clarification:
...
Testing CR501 & CR502
CR501 Anode to Gnd.= 0.66V            Cathode to Gnd.=047.5mV   DROP=0.7V
CR502 “…………………” = -047.3mV        "…………………… “=-0.73V        Drop=0.69V 
Did you mean "Cathode to Gnd.=047.5mV" is -047.5mV (minus) ?  It should be the same as CR502 anode.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #7 on: February 02, 2024, 10:30:40 pm »

2/2/24
Hello Mark, day 2.
This is as far as I got. Some emergency personal stuff came up, I don’t think I’ll be back in town until Mon the 5th. Thanks for your help, it's just getting interesting. I also noticed U33 and U37 getting hot there on A2 with option 001. On page 10.6-5 OR 236 in acrobat. Maybe there supposed to hot.
PS: Yes, CR502 anode is the same my mistake
I can’t tell if R527 is getting hot It’s between a cap and Q502. The voltage on R527 = -21.2V to ground and 2.8v across it.
The voltage at the junction of R518 & R519 is -026.5mV
The voltage across VR501 is 0.24V and at VR502 its 12.3V
Thanks, Mick.
 
 

Offline MarkL

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Re: 8116A Code 42
« Reply #8 on: February 07, 2024, 11:28:02 pm »
Not sure when you might get back to this, but I had a chance to extract and open my 8116A and I made some measurements on the points from my previous posts so you can compare with a working unit.

First, in text form:
  Settings
  --------
  No Waveform selected
  Amplitude 900mV
  Offset 0mV
  Output enabled
  Freq 1kHz (does not matter)
  Duty 50% (does not matter)
  30 minute warmup
  All voltages with respect to GND (using GND testpoint near the
   large electrolytic capacitor in the power supply section)

  +24V: +24.0729
  -24V: -24.0089
  +15V: +14.9824
  -15V: -15.1512
  U501.7: +14.9222
 
  Q501: E+0.100942  B+0.74338 C+10.6051
  Q502: E-0.105894  B-0.75663 C-10.7324
 
  R518.R519: -0.0022828
 
  CR501: A+0.74359    C-0.0047704
  CR502: A-0.0047704  C-0.75784
 
  U501.6: -0.46839
  Q514E.Q515E: -0.165501
 
  U502.6: +0.0049809
 
  VR501: A+10.6072  C+22.6236
  VR502: A-22.5623  C-10.7285
 
  Q503: E+21.9350  B+22.6268  C+23.2524
  Q504: E-21.8193  B-22.5627  C-23.1768


The above is a lot to probe and digest, and some of the things I suggested in my previous post are duplicates of the same node.  With this many nodes to probe, a better way is to put the measurements right on the schematic, which also makes it easier for troubleshooting.  Attached is the schematic of the output amplifier annotated with the above measurements.

Because the ground I'm using is physically far from the output circuit, there is a consistent small drop of around 2mV for most of the readings.  This ok as long the same ground is used for all measurements.  See photo for suggested ground point.

U33 and U37 should be warm, but shouldn't be so hot you can't keep your finger on them.  I measure them around 42C.  The four chips in that row are ECL, so they tend to use a lot of power and run hot.

My Q501 and Q502 are also quite hot, around 65C.  There are other components that are running even hotter, like R530, R531, and R532 which all seem to be running around 82C.  U401, the shaper IC, is running at a balmy 73C.  I never looked at the insides of a 8116A with a thermal camera before.  Wow, it's a really toasty unit.

I'm starting to wonder if the collector of your Q501 is open.  Q501 has a reasonable bias but doesn't seem to be doing anything.  You could take it out and test it.  You could also try a test in-circuit and try to force more bias current into the base by temporary holding a 10k in parallel with R516 (an 11k) and see if there's any voltage change on Q501's collector or emitter.

As per my previous post, it would be interesting to know what the voltage is at the base of Q503 (which is also the cathode of VR501).  VR501 is also a suspect, but not proven innocent or guilty yet.
 

Offline MarkL

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Re: 8116A Code 42
« Reply #9 on: February 08, 2024, 08:20:12 pm »
Here's another thing if you could please clarify:
...
results Q502 =
E.- testing at R519= -111.3mV
B.- testing at CR502= - 0.746mV
C.- testing at VR502= - 8.888V

...

CR501 Anode to Gnd.= 0.66V            Cathode to Gnd.=047.5mV   DROP=0.7V
CR502 “…………………” = -047.3mV        "…………………… “=-0.73V        Drop=0.69V 
...

Did you mean that Q502 B is at -0.746mV or -0.73V?  It would make more sense if it was the latter.  Please take care to be accurate in recording voltages.  It adds a layer of difficulty having to guess what was meant.

Because this is an inverting amplifier with feedback, we should also consider what's coming back towards the input on the feedback path since there might be something faulty downstream of the stages currently under scrutiny.  A good place to measure the feedback node would be the junction of R528 and R529.  Can you check the voltage there too, please?  Mine reads +0.0026147V (same settings and ground reference point).
 

Offline MarkL

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Re: 8116A Code 42
« Reply #10 on: February 09, 2024, 03:29:52 pm »
Analyzing this a little more closely, I want to correct something I said:
...
And looking at the unit's final output, clearly it's stuck above 0V when the waveform should be more or less symmetric around 0V.  So something is wrongly dragging the output high.  Q502 is one of the intermediate drivers trying to pull the output low, so it's not a surprise it's hot.  It's probably fighting against something that's keeping the output high.
...
First, we've determined Q501 and Q502 just run hot, when comparing to a working unit.  So the elevated temperature of Q502 may not be a useful clue.

Second, I was not taking into account the inverting stage in this amplifier (which happens at Q505 and Q506).  So, when the collector of Q501 goes high, the output is forced low.  Therefore, the collector of Q501 might actually be doing the right thing by being pinned high, as instructed by the feedback.  It could be trying to correct for whatever is dragging the output high.

I'd like to add Q507 to the list of measurements.  It sits conveniently between the inverting gain stage (Q503/Q505 and Q504/Q506) and the output driver (emitter follower) stage consisting of Q508/Q510/Q512 and Q509/Q511/Q513.  It may at least help divide the schematic in half for your troubleshooting focus.

Let's also take a look at voltages around Q508 and Q509, since that's where you had to replace them and their associated collector resistors (R559 and R560).  Maybe there's something else dead in the output driver section that you didn't catch.

Note that Q510/Q512 are essentially in parallel with each other, as is the pair Q511/Q513.  They should be sharing currently equally and a quick check should show the emitters in each pair to be at the same voltage, within a mV or so.

I should have some time later today to update my diagram with measurements for these nodes and will repost.
« Last Edit: February 09, 2024, 03:32:18 pm by MarkL »
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #11 on: February 09, 2024, 07:10:01 pm »
I didn't read the above post yet. I'll be Back.

2/9/24

Hello again Mark, these are the newest measurements. Your schematic idea is brilliant. I was going to edit yours, but I have Adobe Acrobat Pro X, and it doesn’t have the fonts (LibreOffice) has.
I’m having a major issue with my Saab someone stole the ECU. And now I have to learn how to work a Tech 2 Scanner, and the software it uses THAT ONLY WORKS IN XP! Had to bone up on VMware. The updates need to be downloaded (I don’t think XP will access the internet, so I must find the files on the internet and figure out how to get them to load in the software in XP. You can just buy an ECM and reprogram it USING your OLD ECM. See the problem?
 This part is supper complicated, and I’ve only scratched the surface. 
The ECM must be married to the ECM apparently through the security system I have been reading into all hours of the night. For the moment until a few more hours are added into the day is it OK if I forgo the schematic until I get caught up and just post the results.

I used the settings & Gnd. locations noted.

+24v:    +24.0140
-24v:     -24.0123
+15v:    +15.0319
-15v:     -15.0273

U501.7: +14.04263

Q501:    E +066.501mv     B +0.6592v     C +023.8454v
Q502:    E -069.3mv          B -0.7245v     C -08.868v NOTE: these are fluctuating up & down.

R518.R519:  -016.9463mv

CR501:   A +0.65984v      C -035.46mv
CR502:   A -0.2474v         C -034.67mv

U501 . 6:  +013.5805v NOTE: yours is neg.
Q514

Q515: E +012.8370v NOTE: yours is neg.

U502. 6:   -21.2336mv NOTE: yours is pos., and this starts out at -100 and drops to 21. And then starts climbing.

VR501:   A +023.1866v     C +023.9821v
VR502:   A -021.3346        C -08.8716v

Q503:   E +02.23366v       B +23.9812v       C +02.6464v
Q504:   E -020.5156v        B -021.2258v      C -023.6773v

Tempts FREAKEN HOT!! Using UNI-T:  uti260B
U33:  78c
U37:  80c
Q501:  32c
Q502:  53c
R530,31,32:   76c
U401:  74.5c

NOTE: a lot of the voltages were fluctuating,
I also tried jumping R516 w/10K no changes,
Removed Q501 Using a small transistor tester, it tests good. This a 2N2369A
I have NOS   Q501 and 2 transistors coming- it couldn’t hurt.
Thanks Mark
 

Offline MarkL

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Re: 8116A Code 42
« Reply #12 on: February 09, 2024, 11:46:58 pm »
Attached is the schematic with added measurements on the output driver side.  If it would be helpful, I can post the LibreOffice Draw file instead of the PDF.  I can also use a different font if it's picking some weird substitute font.

Let me take a look at your latest measurements and I'll post back.  The pinned output on U501 immediately stands out.  As long as you have waveforms off, I don't see how anything should be fluctuating.

Are you referring to the U33 and U37 on the A3 board where the processor sits, or on the A2 control board?  HP duplicated the U designations on these two boards (how nice of them).  I was referring to the A2 board in my previous post about them being ECL.  But in either case, your U33 and U37 are still too hot, ECL or not.  At the moment I don't think it has anything to do with the distorted output, but it's certainly is something to keep in mind.  Let's focus on the output amp for now and come back to that.


Good luck with your ECM.  I experienced a similar thing with the module security code stuff trying to fix my Toyota Prius about 15 years ago.  After many, many wasted hours, I finally got it to work only to find out the problem was something internal to the motor generator in the engine anyway.  I just take my cars to the dealer now.  I don't give up easily, but they win.
 

Offline MarkL

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Re: 8116A Code 42
« Reply #13 on: February 10, 2024, 12:08:19 am »
And to answer your question about forgoing the schematic, feel free to use text if that's easier.  I put the measurements in the schematic because it's easier to visualize what's going on, but don't let fancy delivery be an impediment to getting the data out there.
 

Offline MarkL

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Re: 8116A Code 42
« Reply #14 on: February 10, 2024, 03:54:31 pm »
Ok, based on your latest measurements there's some issues with and around Q503.

Note that the Q503 B-E junction is nowhere near 0.7V, and the collector should be around +23.3V or more.  It should be +24V - one diode drop from CR503, or R533 could pull the collector voltage even closer to +24V.

So, Q503 appears dead (open B-E junction, >0.7V), CR503 is also dead (open, >0.7V forward voltage, A to C), and R533 too (open, since at those voltages it would be dissipating about 23W and glowing).

I would double check your voltage readings on Q503, and if confirmed pull it out and verify it out of circuit, as well as CR503 and R533.

When double checking voltages, I would also make sure you can see the +24V rail on the upper side of R533 and the anode of CR503.  It's not beyond possibility that there's a fried trace.

If Q503 is indeed bad, it also wouldn't be a bad idea to check R534 and Q505.  The current that killed it had to go somewhere.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #15 on: February 18, 2024, 06:30:24 pm »
Hello Mark, down for parts on the Saab. Well, I was a lot more careful with the measurement's a lot of them not directly connected to the power rails had fluctuating readings as if caps charging. I tried to get the first reading. Where it says mv, that is right off my meter. HP34401A its readings match my Keithley 2015 to within microvolts.
I replaced Q501 because I had a new one and it was already out. I have the TO-93pkg heatsinks so at some point I will replace Q502 also. Looking at the resisters around Q501 and Q503 readings made with 4wire, R516. 10.962k.  R524. 100.437Ω   R525. 2.0012K.  R533. 19.635Ω   R534. 19.599Ω those numbers on the schematic sure look like an 8 but definitely a 6.
I'm going to pull CR503. right now.  Oh ya. notice the polarity difference around U501 & U502?
Thanks, MarkL. 
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #16 on: February 18, 2024, 06:33:33 pm »
For some reason it didn't post my schematic here it is.

UPDATE: CR503 checks fine out of circuit!
AND: found a bad solder joint AT the topside of the MAIN board where Q510 Collector meets the board making a sketchy +24v connection. It was soldered on the bottom but not the top where is gets the +24v Makes me want to test output transistors with heatsinks where you can't see the legs from the bottom of the board at the legs what a pain that will be. perhaps Mark you see some transistors I might want to recheck looking at new voltages? 
« Last Edit: February 18, 2024, 08:37:16 pm by Mick B »
 

Offline MarkL

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Re: 8116A Code 42
« Reply #17 on: February 18, 2024, 09:40:00 pm »
The voltages around Q503 that you're showing on the schematic are very different than those you posted before.  I can no longer conclude there's anything wrong with Q503, CR503, or R533.

The polarity difference wrt. U501 is not a major concern.  U501 is providing an offset current to the amplifier input to keep the amplifier's virtual ground at 0V to compensate for imbalance due to component variability.  So, it could come to rest at any value ideally close to 0V.  But because the amplifier is currently way out of balance due to whatever failure (note mid-point between Q501.E and Q502.E), U501 is pinned to one side as a side effect.  I've learned to never rule anything out completely, but I don't see anything at the moment that leads me to believe there is  a problem with the way U501 is behaving.

I'm seeing some voltages around Q512 that don't make sense: How can it have +0.36152 on its emitter when the base, collector, and other side of the emitter resistor are all higher than that?

Before we go any further, can you describe the "fluctuations" you're seeing?  Or maybe put your scope on a couple of the nodes where you're seeing a lot of fluctuation?  It's not out of the question that in its current failure mode the whole amplifier is oscillating.  Obviously it shouldn't be, but that would make it impossible to obtain stable voltage measurements.

Are the power supply rails stable according to your scope?
 

Offline MarkL

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Re: 8116A Code 42
« Reply #18 on: February 18, 2024, 10:19:04 pm »
In addition to the above, fluctuations notwithstanding, the voltage on the collector of Q506 is not making a lot of sense.  I'd like to know what kind of current is flowing through the emitter.  Can you take a look at the emitter voltage on Q505 and Q506?  We can determine the current from the emitter resistors R534 and R537.  Thanks.
« Last Edit: February 18, 2024, 10:39:04 pm by MarkL »
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #19 on: February 20, 2024, 10:23:56 pm »
In addition to the above, fluctuations notwithstanding, the voltage on the collector of Q506 is not making a lot of sense.  I'd like to know what kind of current is flowing through the emitter.  Can you take a look at the emitter voltage on Q505 and Q506?  We can determine the current from the emitter resistors R534 and R537.  Thanks.

Hi Mark, Ok I spent all day yesterday looking over voltages I am dyslexic and i have to make multiple measurements and read them over and over to make sure I have not transposed numbers and since my first set of numbers, I have been diligent in this. and trying to make since of these voltages. I left question marks at some of the fluctuating numbers. I circled just 3 the numbers were any ware from 0.32??? to what you see in the circles Just an hour or so apart, and it had been warming up well over an hour. This is what I mean by fluctuating the last 3 digits do not stop sometimes changing 2nd digit. the Power supply is rock solid. I looked at a few nodes with my scope really nothing to see just DC voltage, I saw no AC until I got down in the weeds @ 50mv = noise. (I had that thing running all day the 2 ICs on the A2 board haven't caught on fire yet). :-+
When it rains, went to post this yesterday and I internet went down. the same network I had up 5yrs or so no issues, I saw ATT workers at one of their junctions where a lot of their stuff meets. I'm sure they did it. My whole house is wired with Ethernet, using a Cisco 48 port switch & an ATT, fiber router/modem with typical default IP address, long story short. all of a sudden my switch has the same IP add. as the router. That took a min to get to the bottom of and fix. 
« Last Edit: February 20, 2024, 10:27:23 pm by Mick B »
 

Offline MarkL

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Re: 8116A Code 42
« Reply #20 on: February 21, 2024, 11:02:21 pm »
Regarding your description of "fluctuations", it appears you are getting readings that are unstable in the mV in most cases.  It could be noise or possibly a low level oscillation, but you are not seeing anything on your scope.  I'm going to assume for the moment the digits you've shown are stable and valid, and ignore any digits with a "?".

One thing to try is to set your DMM on AC and see what kind of readings you get on some of these nodes that are unstable.  This will block the DC and show just the varying part of the voltage on that node (within the frequency limits of your DMM).

As far as the latest updated measurements, there are several items of note:

1) Q506 B-E junction is significantly more than 0.7V (approx. 3.2V).  This would indicate Q506 B-E is open.  I would remove Q506 and check it out of circuit.

2) Q505 is off, as indicated by the B-E voltage of only about 0.4V.  The collector is therefore floating, and free to wander around (within the bounds imposed by other circuit components attached to it, such as other transistor junctions).  Even connecting your probe to the collector could be influencing the reading.  This could be the reason for the unstable readings.

3) Both Q510 and Q512 also have B-E junctions > 0.7V (approx. 0.9V to 1.0V).  Recall that they are in parallel, and this would indicate neither is working.  I would remove them both and test out of circuit.

I would try to correct #1 first and leave #3 alone for the moment.  Let's find out why Q506 is not reading correctly, fix it, and then move on.  Taking a shot-gun approach and changing multiple things at the same time creates too many variables.

You stated in the beginning that you replaced a large number of transistors.  When checking Q506 out of circuit, make sure it is the right type, PNP or NPN.  You might also want to purchase a transistor tester, as it will identify the transistor type, the pinout, and other important parameters like gain (hFE) and leakage.

For reference, my Q505.E is +22.6483V and Q506.E is -22.5548V.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #21 on: February 24, 2024, 12:01:42 pm »
I pulled Q506 and sure enough it was toast! Q506 & Q505 have the heatsinks on but not the cross bar they got very hot, can you tell me what your temps are for these transistor's before I move on. and the good news NO CODE!
Note: the settings were as you recommended, also all the pots on the main board are centered.
Thanks
« Last Edit: February 24, 2024, 12:09:55 pm by Mick B »
 

Offline MarkL

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Re: 8116A Code 42
« Reply #22 on: February 24, 2024, 03:06:16 pm »
I pulled Q506 and sure enough it was toast! Q506 & Q505 have the heatsinks on but not the cross bar they got very hot, can you tell me what your temps are for these transistor's before I move on. and the good news NO CODE!
Note: the settings were as you recommended, also all the pots on the main board are centered.
Thanks
So, have you replaced Q506 and it now has no error code, or do you mean there is no error code with it out?

My calculations for my Q506 show that it's dissipating about 0.6W when quiescent.  Without a heatsink on such a small part I could see why it's getting quite hot.  I wouldn't run it that way for longer than what's needed to get a very quick check done, maybe less than a minute or so.  The Q505/Q506 heatsink temperature on my unit after a 15 minute warm-up is 60C.  With the case open there's not much airflow directed across it.

How did all the pots get centered?  Were they that way or did you do that?
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #23 on: February 24, 2024, 05:17:28 pm »
Ok I replaced Q506 fired it up and error code 42 is gone. I put the heatsinks on. It still has some issues, I'm doing a rough calibration on it so far it is doing ok, those 2 IC are still blazing hot. The pots were centered by the guy I got it from, He was going to calibrate it that's when he dropped the screwdriver in it, and why I ended up with it. Just going to try and get it in the ballpark before the next big dive. Unless you (MARKL) think I should start else ware in this endeavor. Thanks   
« Last Edit: February 24, 2024, 05:22:39 pm by Mick B »
 

Offline MarkL

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Re: 8116A Code 42
« Reply #24 on: February 24, 2024, 10:22:23 pm »
Centering of all the pots by the former owner was not a great move.  I can say from experience these units can be a real bear to align.  Some of the pots are way too sensitive, i.e. a small movement can radically change parameters, and there is interplay among some that can be difficult to optimize.  It's much easier to start where it's almost right, and then tweak whatever is necessary.  Oh well.

At this point, if something isn't working right, it would be more difficult to say if there was another bad component or an adjustment that's way out.  I agree you should try to get through the adjustment procedure.

On the hot chips, you mentioned they were on the option 001 A2 board.  On page 8-20 of the service manual, there is a short verification procedure for option 001.  See if it passes.
 

Offline MarkL

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Re: 8116A Code 42
« Reply #25 on: February 25, 2024, 02:38:13 pm »
An additional thought on the hot chips A2U33 and A2U37... They are ECL and powered by a -5.2V rail.  You probably have gotten to adjust it already, but if the -5.2V rail is too negative due to "pot recentering", it could be causing extra heat dissipation.  The -5.2V rail is adjusted with A1R12, as shown in the table on page 9-3, along with the other rails.

ECL is fairly robust, but if presented with too extreme a supply voltage, one or more chips could have sustained damage.  Just a theory.

Please post back your progress on the adjustment procedures and the option 001 verification when you can.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #26 on: February 26, 2024, 03:57:45 am »
Greetings, well I got to the end Pg. 9-8. I changed 5 pots for 10 turn pots, yes, the averaging out (for lack a better term) a little here a little there and when there both right move on to the next. It's very time consuming. When I got to Overshoot & Transition Time adjustments, after setting it up correctly the overshoot was always less than<4% but fluctuating. At Steps 5 & 6 is where I noticed a voltage problem at 200mv it was off the screen. I unhooked everything and checked the voltages, and they were way off 2v was 3.19v and so on. Can you explain step 20 Pg. 9.7 I don't understand where to, or how to check the transition time. I'm just not sure what transition they are referring to or how to measure it. 
I kept on, trying to get things in the ballpark. But ended up starting over and decided that to get the first adjustment step5 Pg.9.4 the voltage at 16v is... well look at the square wave photo " The first Procedure." The purple trace is the tracking output. also, the crossover distortion Photo " crossover" seems only to happen at high voltage, I can pin it down. I am wondering if it's because I only changed Q501 Its Hfe was way higher than the one I took out perhaps it's a mismatch, I have a new Q502 in a TO-92 pkg, but I also have the heatsinks for it. also, I just changed Q506 I have to do some checking to find out if I changed Q505 earlier I think I did. will see. I will deal with the IC later unless I'm thinking one problem at a time. but I could be wrong. (it happened once before)   
     
 

Offline MarkL

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Re: 8116A Code 42
« Reply #27 on: February 26, 2024, 08:57:57 pm »
Unless the pots had issues, I would have left them alone.  Depending on what you put in, and where, some 10-turn pots are wirewound and the internal coil of wire adds inductance to the circuit.  In an amplifier that runs up to 50MHz, it could be significant.  I really have to emphasize "if aint't broke, don't fix it".  Especially in the middle of a repair where the thing you're replacing is known working.  It adds more unknowns to what might be wrong.

Transition time (aka rise time or fall time), is how long a signal takes to get from one plateau to another.  A square wave is used for the calculation here.  A change from one voltage level to another doesn't happen instantly, and can be seen as a fast ramp.  The measurement for transition time is the points on the ramp between 10% and 90% of the starting and ending voltage levels, where the difference between starting and ending voltage levels is defined as 100%.  I don't have a Rigol scope, but I'm sure it has a button to measure it automatically for you, probably under the "Measure" menu.  You need to have your horizontal sweep set fast enough so that you can see the ramp of the signal.  If you're curious what it's doing, search for "measure rise time on an oscilloscope" for the old way of manually doing it.

The square wave is not looking great, and it may be related to the crossover issue.  What does it look like at a lower frequency, say 10kHz?  Looks like you have it set to 100kHz in the screen shot.

For the unusually high output voltage, I would start with verifying the amplifier input at TP4 as described on page 10.4-1 1.  If the input isn't right, certainly the output won't be.

In the one scope capture you say the purple is "tracking output"?  Do you mean the trigger output?

The crossover distortion could be caused by very mismatched hFE pairs, or it could be something wrong with the bias in one of the stages.  The transition from the positive side of the amplifier driving to the negative side, and visa-versa, is discontinuous.  You could try changing the frequency of the waveform and observe what it does to the distortion.  If it's less of a problem at lower frequencies, and the distortion gets closer to 0V, it's a problem with the speed of the changeover, perhaps capacitive in nature.


Also, note that the adjustment procedure has you constantly putting in attenuators and taking them out and changing the multiplier on the scope.  This is because HP has chosen an insanely over-powered 20GHz scope for the adjustment procedure that can only do 1mV/div to 80mV/div.  So, all these attenuators are compensating for the scope's deficiencies in this application.  Instead, you can simply put a 50 ohm terminator on your scope (or use the internal 50 ohm termination if it has one) and set the scope according to the needed V/div for any particular step.
 

Offline MarkL

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Re: 8116A Code 42
« Reply #28 on: February 27, 2024, 03:33:34 pm »
Also, it may be worthwhile to re-visit the static operating points on your unit now that it's partially working.  I don't think you need to re-post all fresh readings from your unit since that's a lot of work to transcribe them, but you should compare again to a working unit.  You might find an area with incorrect biasing that is contributing to the distortion.

I've included my readings again below, updated with the two nodes from a few posts ago.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #29 on: February 27, 2024, 05:40:45 pm »
Hello again, just an update. The voltage for the -5.2 rail is set at -5.4 I could not get it to adjust, and then I found this in "UPDATEING/CHANGES/ERRATA Pg.11 this mod had been done. I set the voltages the day I got it, it had no -24v rail. I also did the option 001 verification procedure test it produces a square wave, but it is always on there is no timing function it starts as soon as the output is on and does not stop the counter will continue forever.
And yes, I meant "trigger output" my-bad. and I know what rise and fall times are (you presented a great explanation) DOH! I just couldn't put the two terms together.
I dissected one of my 10 turn pots they are carbon, the ones that were in there should have been 10 turn to start with to call them sensitive is an understatement.
I wondered why all the attenuation, I'm so glad you explained what that was all about. that will shave off a lot of time.
Without the attenuation nonsense I have not been able to reproduce the crossover distortion, YET. I'm going to re-due the calibration today. and take measurements after.
Thanks, Mick
 
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #30 on: February 28, 2024, 10:59:16 pm »
Where to start? this is a half-ass calibration. It went through the procedure up until Pg.9-11 step 7. any width parameter higher than 984 turns on the error light. I putzed around after that. I still have voltage issues and the wave forms start to lose their shape around 7MHz. apparently, there is settings after the Power Supply Preliminary because from Pg.9-3 to 9-7 all to voltages are good up to 16+ volts the and the rise times are < 6.6 but fluctuate a lot. Pg. 9-7 step has to be a misprint. these settings put the signal off the top and out of sight. And then the voltages turnout low?
These are the voltage readings from Amplitude & Offset Performance Test. Pg.8-9 Just posting my results. in The Updating Chapter Pg. 8. there is an update for Offset voltages, & DC Output.  Unfortunately, these won't help my readings.
8v =
RMS 
Sine 2.72v
Trangle 2.23v
Square 3.70v

3v =
Sine 1.036v
Trangle 0.862v
Square 1.425v

1v =
Sine 0.344v
Trangle 0.299v
Square 0.494v

100 mv =
Sine 034.26mv
Trangle 029.78mv
Square 049.14mv

OFFSET
@ 100mv
7.50v =7.46v
5.0v =4.97v
3.0v =2.98v
1.0v =0.957v
100mv =090.8

@10mv
795mv =0.719mv
500mv =0.453mv
100mv =092.4mv

Frequency Performance Test Pg.8-2
50MHz = 50.047MHz
10MHz = 10.086MHz
10kHz = 10.082
1kHz = 998.8Hz

DUTY %
1Hz @ 10% =9.28%. @50%. =47.68%. @90%. =89.02%.
1kHz @ 10% =10.104%. @50%. =49.97%. @90%. =89.87%.
9.99MHz @ 20%. =20.00%. @50%. =50.18%. @80%. =80.00%.
Mark where do you think I should measure first? to take static measurements with the heatsinks on??  if you can pinpoint what nodes we might want to look at I will take a picture of the backside of the board remove the heatsinks and use a bright light to find the nodes on the backside and mark them on the photo so I can find them how did you measure yours?
     
« Last Edit: February 28, 2024, 11:17:30 pm by Mick B »
 

Offline MarkL

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Re: 8116A Code 42
« Reply #31 on: February 29, 2024, 09:58:14 pm »
On width >984us errors, the test frequency is supposed to be 900Hz.  Are you getting that on the output?  Check that you have the proper voltages on the width controller IC U300, page 10.3-17.  On my unit the error light turns on at 1.10ms.  I'm not very familiar with the operation of U300, but the manual says error is asserted when the next trigger happens before a pulse cycle is complete.  So, my guess is that something is off with the duration of the pulse high, low, or repetition rate (frequency) that is making the cycle last too long.

On the poor looking waveforms >7Mhz, keep in mind the transition time of the square wave is 6.6ns or a little less.  In this unit, transition time is a constant since it's a limitation of (at least) the output amplifier.  As the square wave gets higher in frequency, the transition time will consume more and more of a waveform cycle.  By the time you reach 50MHz, the transition time will dominate and the waveform will look almost like a sine wave.

In terms of measuring, I did a lot of mine from the back when the heatsinks were in the way, and I used a flashlight from the top side to cast a shadow to verify I was probing the right pad underneath.  On some of the probe points, sometimes you can find a resistor or diode lead that's the same node and you can measure from the top.

Also keep in mind this unit is essentially an analog function generator that has a microprocessor instead of knobs.  Many of the adjustments are just calibrating the digital display to analog voltages that control frequency, amplitude, pulses, etc.  Because the it's all analog, don't expect precise output for anything like you would on an arbitrary or synthesized waveform generator.

This last set of waveforms you posted are not so bad for the 8116A, but the square wave could be flatter on the bottom, and the triangle is looking a little non-linear on the downward slope.  Again, maybe the crossover distortion is still getting you.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #32 on: March 01, 2024, 02:29:38 am »
Thanks Mark, your help has been invaluable. I was testing the WID settings at 900Hz and @ 100us I got 102 on the counter, but the next setting @ 900us. turned on the error light and like I said it goes out when lowering the setting to 984us turns off the error light I saw -5.3v on pin 9 of U300. I tried hooking up the HP 5005A just because, changing the bridge [W3] to test and changing the jumper to FreeRun turns on the error, STA, DTY, mV and lol lights. It seems locked up, no buttons do anything, having never done this before I don't know what it supposed to do, reset does nothing hooking, up the 5005A does nothing either. where do we want to precede from here?
« Last Edit: March 04, 2024, 04:21:58 pm by Mick B »
 

Offline MarkL

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Re: 8116A Code 42
« Reply #33 on: March 05, 2024, 07:14:11 pm »
To answer your questions...

More explicitly, I was asking how your waveforms compared with the troubleshooting procedure on 10.3-17, not just the voltage on the error signal.  It's fairly certain that the error output on U300 was being asserted correctly.

Free-run mode puts the processor in a tight loop executing a single instruction while incrementing the memory address lines.  The unit does not boot into any operational mode, nor does it even get to any initialization code for the display.  The display is just showing whatever state the latches powered up in.

Because the address lines are incrementing, it allows you to use a signature analyzer to verify ROMs, decode logic, and sometimes other areas that operate independently of the firmware (like the keyboard scan in this unit).


What do I think from here?...  I would go back to the tenet of one thing at a time and finish with the output amplifier repair.  You still have some unexplained crossover distortion, as last reported.  Something is still not right.

I would go through the adjustment procedure and try to adjust everything having to do with output signal quality: voltage levels, linearity, distortion, overshoot, etc.  If you can't get the pulse adjustments right, or some of the other timings right, skip them for now.

After adjusting what you can, if there's still crossover distortion, compare your quiescent voltages with what I posted from a working unit.  I would look for voltages that are unbalanced between the top and bottom drivers in all stages.  If that doesn't turn up anything, output a sine wave and try to find a frequency where the distortion is the worst, and take a look at the waveform along the heavy lines (signal path) shown in the schematic.  Again look for a stage where distortion starts to be introduced, or possibly where it changes (like it's inverted).  Because this amplifier has feedback, keep in mind the feedback is trying to compensate for distortion problems, so you might see some nodes that look distorted but it's actually the correction from the feedback.

And double-check the input of the amplifier to make sure the signal going into it is distortion-free.

If you were able to adjust out the crossover distortion, then great, you can try to get the pulse output adjusted properly and pick up with the troubleshooting procedure on 10.3-17 (U300).
« Last Edit: March 06, 2024, 02:18:09 am by MarkL »
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #34 on: March 14, 2024, 02:55:21 am »
MarkL, I'm back at it, I have been tied up working on the SAAB, Well the Chinese Tech2 Scanner mostly. To the 8116A, as it became apparent that the CAL was just not going well and seemed pointless so many things would not adjust to specs. and I knew it had mismatched transistors. I replaced Q502 with what is supposed to be a direct replacement A (2N5771) to complement Q501 A (2N2369A) Note: this is a TO-18 package and the 2N5771 is a TO-92. I found some heatsinks that slip on the TO-92 Package. Also, as the manual says if the waveform is distorted on the leading edge look at Q503 and Q505 and Q506 and Q505 have already been replaced so I replaced Q503 with a 2N3094 and Q504 with a 2N3906. It was a bitch doing this with the heatsinks, and the other things in the way.
The GOOD NEWS, every adjustment up until the last step (7) of OFFSET ADJUSTMENT Pg.918 dialed right in even fixed the error light in the width adjustment problem.
Step 7 says if any offset adjustments were required (a very small one) repeat the "Overshoot & Transition Time Adjustment" procedure before continuing. I went back to that chapter and the overshoot was wacked I decided to reboot the 8116A and when it came on E-51 greeted me.  :palm:
I Printed out MarkL's known good readings again. I'm thinking one of the new transistors / HEATSINK. I'm not ruling out a solder joint These were ridiculously hard to solder.
We will see. I was just so happy; it was adjusting out like it was new. Voltage reading forth coming. My memory cards from England showed up and I'm expecting a new VCI module for my scanner, the wife's car takes president.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #35 on: March 18, 2024, 08:10:29 pm »
As my last post stated, something went wrong in the middle of calibrating this unit. I'm posting the results of my voltage readings after the failure. I had these ready to go but decided to check one last time so to be sure NONE of the readings were transposed (I'm dyslexic) and I will post those readings as soon as I can SOMETHING MORE is very wrong. Mark please what do you see here?
 
 

Offline MarkL

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Re: 8116A Code 42
« Reply #36 on: March 19, 2024, 08:35:28 pm »
One thing that looks really strange is the -13.172V at the junction of R543, R544, R545, and R546.  The other side of those resistors are at a much lower potential and they're all only 10 ohms, so either they're cooking or they're open if all those measurements in that area are right.

Can you double check that node?  And on the other side of R547 since it's also at approx. -13.2V?

I'm not sure where the extreme negative voltage might be from, except maybe there's something wrong with CR513?
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #37 on: March 21, 2024, 01:38:39 am »
Hello all, while I was going to go over the voltages one last time, but after the error 51 showed up the voltages were so bad and so far off "negative voltages everywhere". it was just to ridiculous to post. I pulled Q512 and it testes good. put it back again, tweaked a few pots and NO error 51 its gone!   :-//
I apologize for the erroneous voltages Mark noted, it was milli-volts at R547 & R545~R546 
Please use these voltage Number 4.PDF file.  Looking at TP4 & pins 18 & 19 of Q401 they test OK except the voltage on TP4 is low by about 1/2. Pg 10.4.12 fig. 10.4.7 on the 1v test, as the voltage goes up these stay the same. see Triangle.JPG.
I'm going to try to recalibrate up to the Shaper, just to see if I can get the basics going again, I don't know what happened, to cause error 51, but that needs to be found.
Mark as always, I will defer to you. Thanks
 
« Last Edit: March 21, 2024, 01:04:10 pm by Mick B »
 

Offline MarkL

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Re: 8116A Code 42
« Reply #38 on: March 21, 2024, 09:38:51 pm »
The voltage at TP4 should be a constant +/-0.5V peak when the output is set to 999mV, 10.0V 9.99V, or 16.0V.  The voltage at TP4 is fed into a set of relay-controlled attenuators that set the final voltage going to the output amplifier.  See the explanation on page 10.4-3 for more detail.

As for the readings at TP4 being low by 50%, first verify your scope is reading ok by looking at a fixed voltage.  Measure something not in the 8116A that you know is right.

Check the reference voltage on the upper side of R411.  It should be about 6.1V.  The adjustment of R410 affects the amplitude, so it might be misadjusted.  I don't know if it has the range to result in 50% like you're seeing, but it's something you're going to have check/adjust in the calibration procedure.


Your A1 board has seen a lot of issues and more are occurring every time you make some progress.  You might want to consider buying a replacement A1, or even a scrap 8116A and take parts from it.  There are also a lot of parts in common with the 8112A, so it would also be a good parts mule.  You can probably get an 8116A for < $80; there's one for $50 being bid on right now with no errors showing.  I guess it depends on your goal in pursuing the unit you have.


EDIT: Fixed voltage threshold; should be 9.99V.
« Last Edit: March 21, 2024, 10:18:12 pm by MarkL »
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #39 on: March 23, 2024, 02:56:14 am »
I made it farther through the cal. this time, most of it. I skipped over some of the shaper adjustments mostly THD Harmonics I have a Siglent 1032X spectrum analyzer but at these low frequency's I am finding the FET in the Rigol MSO5354 to be most excellent. This is where I stopped tonight, at the beginning of Amplitude Modulation Pg. 918 so far so good. This cal. straightened out the strange triangle waveform. I'm thinking some of the shaper adjustments that call for readjusting all the pots that control the waveform balance NOT the balance between normal out, and COMPL. but pos and neg & amplitude that were already set maybe causing issues. This is my 3rd calibration attempt. so far so good.
I took your advice and bid on a $79 Working 8116A with option 001 and WON! It should be here before the end of the month.
Mark, this has been such a great learning experience, I just hope you stay on, I would like to tackle the smoking hot IC's and try out the HP 5005 Signature Analyzer at some point. This unit has had some issues, I just don't want to be defeated. These Function generators are spectacular, I would not like to end up in a landfill. I do not think we are here YET. :horse: After finishing up the basic cal. what next?     
 

Offline MarkL

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Re: 8116A Code 42
« Reply #40 on: March 23, 2024, 10:33:59 pm »
A working one - that's even better!  A working unit of anything makes a great comparison reference to fix a dead one.  Duplicate the settings and start comparing various nodes in the trouble area with either a DMM or oscilloscope, or even signature analyzer.

The scope FFT is definitely the right thing to adjust the harmonic distortion on these units.

It's always a great goal to prevent more landfill and it's why I like fixing this old equipment.  It's often a lot slower with less features than their modern counterparts, but a volt is still a volt, and great bargains can be found.  I think the only exception to that is oscilloscopes  They are such a valuable tool with ever increasing ease-of-use and analysis features, that it's worth the investment to refresh every 5 to 10 years, at least in my opinion.

I have a few things that are beyond repair, and in general I have a working version too.  I keep the dead one for parts, which also keeps it out of a landfill.  But I always make sure it's clearly labeled as broken, and I also mark the areas where I remove parts so when I look at it years later, probably for another part, I'll know what I did to it (hopefully).
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #41 on: March 24, 2024, 05:03:02 pm »
I'm am going to give this a rest. I will be back investigating the very hot IC's Thanks for the help.
 
 

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Re: 8116A Code 42
« Reply #42 on: May 12, 2024, 04:27:54 pm »
Hello MarkL been awhile, hope all is well.  I dove back into this thing with a performance test I got to the burst test and ran into problems. the burst outputs a signal but does not stop at any BUR setting. so, I thought I would go look at 10.3 troubleshooting VCO & Width Gen. it passed up to waveform selection, table 10.3-8 is there is an issue. The 1st test in the table WF2 & WF1 both L (OK) 2nd test, WF2 only L on Sq wave and WF1 only H on Sq wave. I stopped at this point not sure if I'm doing something wrong or if this is a problem and where to go next.
Settings= I.BUR, 9.99 mHz @ 1v
 
 

Offline MarkL

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Re: 8116A Code 42
« Reply #43 on: May 14, 2024, 03:26:35 pm »
Given that burst mode is not working, and your U33 and U37 on the burst option board (middle board) are roasting hot, I would focus on that first.  I'm assuming this is still the case.  Not saying that there isn't something strange or possibly faulty with your results in table 10.3-8, but one problem at a time.

The burst control circuitry is ECL, which will run hot, but not around 80C that you mentioned before.  I would take a look at the power supply going to U33 and U37.  It should be -5.2V.  Since the other ECL chips are not unreasonably hot, it's probably ok.

As a cursory check, take a look at the logic level inputs and outputs on both these chips.  You should see voltages in this range for outputs, and for inputs that are not externally tied low or high:

  ECL switching levels
                  Min    Typ    Max  (mV)
                 -----  -----  -----
    output HIGH   -980   -895   -810
            LOW  -1950  -1790  -1630
    input  HIGH  -1130   -970   -810
            LOW  -1950  -1715  -1480

In particular, outputs that are very negative could be causing heating issues since ECL outputs only have an emitter follower with the collector tied to 0V.  The output could be fighting a short to -5.2V, for example.

If this is all ok, we'll need to dig deeper and verify that the logic functions implemented by the chips are ok.  I wouldn't conclude these particular chips are dead since it could be something external.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #44 on: May 17, 2024, 01:20:22 am »
Hi Mark, glad you're here. After I did this, I decided to swap the A1 Board between the 2 WOW! some disassembly was required the cooling solutions were not the same, ran through a quick check the voltages spot on, over and undershoot < 4% & Rise times < 6ns. this new board is working well.
 I did not know where to set this to check ICs U33 & U37 so punted. Frequency 1K Amp 1V. EBUR mode, EBUR 3. (I'm sure I will have to do this over.) but for now.
U33 MC10104P
Pin 1. VCC -021.27
INPUTS
A pin 4. -03.1582
A      5. -01.7686
B      6. -058.474
B      7. -03.1481
Pin 8. VEE -0.5288
C     10. -0.3147
C     11. -0.8178
D     12. -0.9851
D     13. -0.7788

OUTPUTS
A pin 2. -0.7974
B      3. -0.9647
C    14. -0.7581
D    15.  000.
        ______
D      9.OUT -03.1471
Pin    8.VCC 2. -05.288
*********************************
U37 MC10103P
PIN 1. VCC 1. -020.031
INPUTS
A Pin   4. -02.716
A        5. -02.714
B        6. -0.9660
B        7. -0.7982
PIN 8 VEE -05.2925
C       12. -01.8690
C       13. -01.8310
D       10. -052889
D       11. -02.6613
              _____
C PIN   9. OUT
PIN     16 VCC2. -02.389

Temp's in IC U33 = 79.3 C and U37 = 65C Note: I have new chips
These voltages don't look good. If I tested them right.
 

Offline MarkL

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Re: 8116A Code 42
« Reply #45 on: May 17, 2024, 03:46:19 pm »
I didn't provide test conditions, sorry my bad.  You should measure U33 and U37 with burst off and with waveforms off.  The idea is to create static conditions to make it easier to look for unusual voltage levels.  I think burst/waveforms off will do it, but I'm not going to be able to get my 8116A on the bench for a week or two to verify.

You could also do these measurements with your oscilloscope.  That way if I'm wrong and something is still switching, you can see the high and low levels.  Unlike the analog circuitry, the counter section is digital so precision voltage measurements are not that important.

To simplify, you're looking for:

  Typical (simplified):
    1 = HIGH = -0.90V
    0 = LOW  = -1.75V
    Swing = 0.85V

Unused ECL inputs may be left open or tied to anything <= -1.75V for logic LOW, or tied to -0.7V for logic HIGH.  There are some exceptions to this for specific chips, but not these.

Check power on U33 and U37: ECL Vcc pins 1, 16 should be 0.0V (GND), and Vee pin 8 should be -5.2V.

In the results you posted, I think you are mixing up mV and V and decimal point placement in several places.  Please be accurate and indicate units for sharing results.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #46 on: May 18, 2024, 02:05:44 am »
Looking over my last post there are some decimal points in the wrong place. I will be more diligent. dyslexia sucks.
Setup. amp. 100mv, offset-0, no frequency, mode Normal.
Pins 8 VEE on both IC's is -5.19V Pins 1 & 16 VCC are 0v
IC-37
Input pins
A4. -2.55V
A5. -2.44V
B6. -0.82mv
B7. -0.77mv
D10. -5.19V
D11. -2.63V
C12. -1.84V
C13. -1.81V   
Output pins
A2. -3.12V
B3. -3.12V
D14. -0.80mv
C15. -3.71V
      ___
C9. out=0

IC. 33
Input pins
A4. -3.12V
A5. -1.75V
B6.   58mv drops to 0v
B7. -3.12V
C10. -3.12V
C11. -0.80mv
D12. -0.96mv
D13. -0.76mv
Out pins
A2. -0.78mv
B3. -0.95mv
C14. -0.75mv
D15. -0v
      ___
D9. out -3.12V

These voltages look almost like the last ones and nothing switching.
used my scope this time. for anyone interested here are the datasheets.
 

Offline MarkL

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Re: 8116A Code 42
« Reply #47 on: May 24, 2024, 12:56:04 am »
Those are some very strange voltage readings.

I measured U33 and U37 on my unit.  Here is a comparison, organized differently.  There was no switching observed on the measured pins.  Temps: U33 is 54C, U37 is 51C.

Good unit settings:
  1kHz, no waveform selected, normal mode (burst off), output on

All readings in V and grouped by gate

Pins:
  (I)  - input
  (O)  - output
  (O-) - inverted output

U33 MC10104 - Quad AND
   Pin     Good     Broken
  ----    ------    ------
   4(I)   -0.774    -3.12
   5(I)   -0.756    -1.75
   2(O)   -0.771    -0.00078
 
   6(I)   -1.75      0.058 drops to 0
   7(I)   -0.774    -3.12
   3(O)   -1.77     -0.00095
 
  10(I)   -0.774    -3.12
  11(I)   -1.87     -0.00080
  14(O)   -1.75     -0.00075
 
  12(I)   -0.93     -0.00096
  13(I)   -0.735    -0.00076
  15(O)    0         0
   9(O-)  -0.773    -3.12
 
 
U37 MC10103 - Quad OR
   Pin     Good     Broken
  ----    ------    ------
   4(I)   -2.10     -2.55
   5(I)   -0.465    -2.44
   2(O)   -0.777    -3.12
 
   6(I)   -1.77     -0.00082
   7(I)   -0.773    -0.00077
   3(O)   -0.781    -3.12
 
  10(I)   -5.13     -5.19
  11(I)   -2.08     -2.63
  14(O)   -0.726    -0.00080
 
  12(I)   -0.77     -1.84
  13(I)   -1.75     -1.81
  15(O)   -0.774    -3.71
   9(O-)   0         0

First, please confirm your readings above before we go chasing anything.  The I/O pins at or near 0V are a problem (I count 10 of them), with the exception of the unconnected outputs U33.15 and U37.9.  Several pins in the 3V range should also not be.

What exactly do you mean "58mv drops to 0v" ?
 

Offline MarkL

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Re: 8116A Code 42
« Reply #48 on: May 24, 2024, 03:38:58 pm »
So, it turns out that the burst section is dependent on the last settings made to it, and those settings remain even if the unit is put back into normal mode.  And sometimes there is still clocking present on some of the pins.

In an attempt to get things as static as possible, I put my unit in external burst mode (E.BUR), which makes everything wait until it gets an external trigger.  And I also made note of the burst count setting since that may matter.  Some of the pins changed state from my previous post and I have updated my readings below.

I think there are bigger problems given the ECL logic levels in your unit, but I wanted to make sure we're looking at a consistent comparison before going further.

Good unit settings:
  1kHz, duty 50, no waveform selected, burst 14 cycles, external burst
  mode, output on

All readings in V and grouped by gate

Pins:
  (I)  - input
  (O)  - output
  (O-) - inverted output

U33 MC10104 - Quad AND
   Pin     Good     Broken
  ----    ------    ------
   4(I)   -1.72     -3.12
   5(I)   -0.756    -1.75
   2(O)   -1.77     -0.00078
 
   6(I)   -1.75      0.058 drops to 0
   7(I)   -1.72     -3.12
   3(O)   -1.77     -0.00095
 
  10(I)   -1.72     -3.12
  11(I)   -1.87     -0.00080
  14(O)   -1.75     -0.00075
 
  12(I)   -0.93     -0.00096
  13(I)   -0.735    -0.00076
  15(O)    0         0
   9(O-)  -1.72     -3.12
 
 
U37 MC10103 - Quad OR
   Pin     Good     Broken
  ----    ------    ------
   4(I)   -2.10     -2.55
   5(I)   -2.09     -2.44
   2(O)   -1.72     -3.12
 
   6(I)   -1.77     -0.00082
   7(I)   -1.77     -0.00077
   3(O)   -1.75     -3.12
 
  10(I)   -5.13     -5.19
  11(I)   -0.470    -2.63
  14(O)   -0.726    -0.00080
 
  12(I)   -0.77     -1.84
  13(I)   -1.75     -1.81
  15(O)   -0.774    -3.71
   9(O-)   0         0

Same questions:

First, please confirm your readings above before we go chasing anything.  The I/O pins at or near 0V are a problem (I count 10 of them), with the exception of the unconnected outputs U33.15 and U37.9.  Several pins in the 3V range should also not be.

What exactly do you mean "58mv drops to 0v" ?
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #49 on: May 25, 2024, 02:41:55 am »
Hay, Mark. Settings MODE= EBUR@ 14.BUR Amp. 999mv frequency is 1K. off Output= on WID = 10.0 ns Offset =0 Duty 50%
what I meant by PIN 6 on U33 it went from 58mv and dropped to 0. It is NOW holding steady at 47mv.
 Using the same format as yours, more or less.

Pins:
  (I)  - input
  (O)  - output
  (O-) - inverted output

U33 MC10104 - Quad AND
   Pin     Good     Broken
  ----    ------    ------
   4(I)   -1.72      -3.13
   2(O)   -1.77     -0.785
 
   6(I)   -1.75      -0.047
   7(I)   -1.72      -3.13
   3(O)   -1.77     -0.950
 
  10(I)   -1.72     -3.12
  11(I)   -1.87     -1.75
  14(O)   -1.75    -1.75
 
  12(I)   -0.93     -0.972
  13(I)   -0.735   -0.776
  15(O)    0         0
   9(O-)  -1.72     -3.12
 
 
U37 MC10103 - Quad OR
   Pin     Good     Broken
  ----    ------    ------
   4(I)   -2.10     -2.70
   5(I)   -2.09     -2.70
   2(O)   -1.72    -3.13
 
   6(I)   -1.77      -0.952
   7(I)   -1.77      -0.785
   3(O)   -1.75     -3.12
 
  10(I)   -5.13      -5.26
  11(I)   -0.470    -2.65
  14(O)   -0.726   -0.784
 
  12(I)   -0.77      -1.85
  13(I)   -1.75      -1.82
  15(O)   -0.774   -3.70
   9(O-)   0            0
 

Offline MarkL

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Re: 8116A Code 42
« Reply #50 on: May 27, 2024, 05:33:55 pm »
Ok, there's a few things we should look at.

The first, as you've pointed out, is U33.6 being close to 0V.  Because this pin was changing slightly before, the pulldown for that node might be open (R62.5).  The easiest way to check is to use a 470 ohm resistor and hold it to pin 6 and Vee (pin 8 ) at the same time while watching the voltage on pin 6.  If you get a normal ECL logic level, R62.5 is open.  You can either replace resistor network R62, or just solder in a stand-alone 470R resistor underneath.  I would probably do the latter since it's easier and you can move on to other areas.

If pin 6 stays near 0V, it's likely the output on U32.5 is toast.

What is the voltage at U33.5?


On U37, three of the four outputs, pins 2, 3, and 15 are unusually low.  The fourth, pin 14, is inconclusive because it is wire-OR'd with two other gate outputs.  I am highly suspicious of U37.  The reference voltage generator in the chip is shared between the gates and it might be dead.

A possible way to check is to make the unused output, pin 9, live by connecting it to Vee through a 470R resistor.  See if you get a valid ECL logic level on pin 9.  If not, it may be time to pull U37.

If you remove U37, I'd recommend 1) put a socket in its place, and 2) check the voltages on all the pins while it's out because the isolated readings may provide clues to other problems.

I'm also noting that U37.2 is wire-OR'd with U33.9, but other sections of U33 appear to be working, which goes against the dead U37 reference generator theory.  I'm not sure what to think of that yet, but it may also indicate an issue with that gate on U33.  Measuring the pins on U37 with U37 out can tell us more.

And as with placing a 470R on U37.9, it may also be useful to make U33.15 live and get a voltage reading on that too.  (U37 and U33 pins 9 and 15 should be complements of each other.)


Another approach when there are many logic gates hanging off a single node, like in this circuit, is to use a logic pulser and current tracer combo, such as the HP 546A (adapted for ECL) and HP 547A.  These allow you to determine where the current is going.  They can be very useful with ECL with its wire-OR'd architecture, and can often lead directly to the culprit.  If you have these, let me know and we can make use of them, but they are not common.  They can be had on ebay, but they command a high premium and not worth it at the going rate, in my opinion.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #51 on: May 28, 2024, 02:29:39 am »
Hay there, I can't believe I left off pin 5 :palm: I went back and rechecked pin 6 again and lost where i was.
U33 Pin 5 is -0.814
I will do all the things you ask. I made an offer on one of those logic probes, between my son and I we have several HP devices. of this era. If he excepts, I should have it by June 6 at the latest. I would like to take this time to go through the manual and see if I can make heads or tails of these ECL circuit's I have a basic understanding, but I can do better. I an hoping by the time this HP8116A gets worked out I will have a complete understanding of this unit and how it does what it does at the circuit/component level. Thank you, Mark.
« Last Edit: May 28, 2024, 02:31:26 am by Mick B »
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #52 on: May 28, 2024, 05:30:22 pm »
Things to report. The logic probe will be here on 6/1. The voltage is up to 58mv on pin 6. and holding.
ALSO you said "On U37, three of the four outputs, pins 2, 3, and 15 are unusually low." did you meant high?
Anyway, using 470Ω  as requested produced.
U33.6       -0.085
U33.15     -0.758
 --------------------
U37.9       -3.43
 
 

Offline MarkL

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Re: 8116A Code 42
« Reply #53 on: May 29, 2024, 03:20:54 pm »
Things to report. The logic probe will be here on 6/1.
I had mentioned the HP 546A Logic Pulser and 547A Current Tracer.  There is also a thing called the HP 545A Logic Probe which is often sold with the other two, but not as useful if you already have a scope.  What is it that's on the way?

If you have not used any of these tools before, you can familiarize yourself:

  https://www.hpmemoryproject.org/an/pdf/an_163-2.pdf

Quote
The voltage is up to 58mv on pin 6. and holding.
Is that +58mV or -58mV?  If +58mV, I'm not sure where it's getting a positive voltage.  Maybe take a look at U32.7 since that signal is coming from a TTL IC with positive supplies.  And if -58mV, it's just wrong anyway since it should be between -1.75V and -0.90V (again, typical values).

Quote
ALSO you said "On U37, three of the four outputs, pins 2, 3, and 15 are unusually low." did you meant high?
No, I meant low.  Those outputs are between -3.70V and -3.13V and a typical ECL logic low is -1.75V.  I'm saying those outputs are very low compared to -1.75V (-3.13V < -1.75V).

Quote
Anyway, using 470Ω  as requested produced.
U33.6       -0.085
U33.15     -0.758
 --------------------
U37.9       -3.43
U33.6 is stubbornly staying near 0V and it shouldn't be.  The output is an emitter follower, so should be one diode drop below 0V (approx. -0.7V) at a maximum.  It could be the output driver on U32.5 is shorted.  The other half of the output, U35.2 U32.2, is connected to U33.5 which you report at -0.814V and is ok.

U33.15 is ok.

U37.9 is very low with the only thing on it being the 470R test resistor.  Again it should be in ECL logic level range.  Both of the outputs on this gate are very low and I'm not coming up with a good model (yet) of how this could be happening.


Below is a diagram of a MECL 10k OR gate, for reference on what's going on inside the chip.  Some of the other gate types are structured differently to reduce propagation time, and unfortunately those diagrams are not available so we can't make too many assumptions when considering what might have failed internally.

The diagram is from the Motorola 1989 MECL System Design Handbook, which has a detailed discussion of the circuit's bias levels and transfer characteristics.  Chapter 1 is worth reading to understand how ECL works, and what could be happening internally when things go wrong.

  http://bitsavers.trailing-edge.com/components/motorola/_dataBooks/1989_Motorola_MECL_System_Design_Handbook_4ed.pdf

EDIT: Typo - fixed reference to U32.2.
« Last Edit: May 29, 2024, 03:49:08 pm by MarkL »
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #54 on: June 01, 2024, 10:30:52 pm »
Wow, Information overload I love it!
This is what I received today HP 546A Logic Pulser. I will no longer call this Logic Pulser a probe. So much reading, I downloaded both of these publications and the service manual for the HP 546A.
Quote
Is that +58mV or -58mV?
It is -0.058
Quote
No, I meant low.  Those outputs are between -3.70V and -3.13V and a typical ECL logic low is -1.75V.  I'm saying those outputs are very low compared to -1.75V (-3.13V < -1.75V).

DOH! I was looking at my numbers being higher than yours. I get it, a lower negative voltage referencing ground. I won't make that mistake again.
OK! I'm going to do a lot of reading. I will get back to you in a couple of days, also I have a couple of other things that need my attention. Thanks again.




 
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #55 on: June 05, 2024, 01:52:03 am »
Hello, I'm still reading. I removed U-37 and took voltage readings @ U-32, U-33, U-37 SOCKET sans the chip. I will do this again after I put in the new MC100103. U-37 chip. The settings are the same.

PINS U-32

4(I)     -2.260
7(I)     -0.461
10(I)   -0.463
12(I)   -5.3
13(I)   -0.810
 
2(O)   -0.813   
3(O)   -1.773
5(O)   -053.6mv
6(O)   -050.6mv
9(O)   -0.816
11(O)  -0.816
14(O)  -1.773
15(O)  -0
VCC PINS 1 & 16 = -013.6mv
VEE PIN 8 = 5.3

PINS U-33

4(I)   -4.266
5(I)   -0.814
2(O)  -0.740 

6(I)    -052.9mv
7(I)    -4.266
3(O)   -0.740

10(I)   -4.266
11(I)   -1.773
14(O)  -1.768

12(I)   -0.984
13(I)   -0.774
15(O)  -0
9(O)    -4.265
VCC PINS 1 & 16 = -016.5mv
VEE PIN 8 = -5.3

PINS EMPTY SOCKET U-37

4(I)     -2.088
5(I)     -2.069
2(O)    -4.266
 
6(I)     -0.771
7(I)     -0.740
3(O)    -5.3

10(I)    -5.3
11(I)    -0   
14(O)   -0.805

12(I)    -1.805
13(I)    -1.488
15(O)   -5.3
9(O)     -0

1 VCC    -016.5mv
16 VCC  -016.5mv
8 VEE    -5.3
 

Offline MarkL

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Re: 8116A Code 42
« Reply #56 on: June 05, 2024, 05:04:01 pm »
Well, that's some interesting values with U37 out of the way.

- Pins U37.3 and U37.15 are now being pulled fully to -5.3V (-5.2V nominal), which is correct.  This says the inputs they are going to on other gates are probably ok, and it was the outputs on U37.3 and U37.15 that were bad.

- Pin U37.2 should now also be pulled to -5.3V but it's not.  Output U33.9 could be bad, or there's an input on that node among the six inputs on U33 and U34 that's bad.

- It's odd that pin 11 is 0V, because that's coming from a level shifted output on U39, a 74LS109.  I would double check that, and check output U39.7.

I wouldn't put a new U37 in just yet until you're satisfied the other connected chips surrounding it are ok.  ECL outputs can sustain an absolute maximum of 50mA on outputs which is easy to exceed with a short or low impedance path to Vee.  You don't want to kill the new U37.

I think I would be tempted to pull U32 next.  U32.5 and U32.6 are both near 0V, and it seems more likely it is a C-E short on both those outputs than an identical input issue on both U33.6 and U34.6.  (This is an example of where the current tracer would help, instead of pulling the chip.)
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #57 on: June 11, 2024, 01:29:19 am »
Hi Mark, VERY EXPENSIVE but
I made an offer on a HP 547A current tracer Should have an answer soon.  When I was reading HP troubleshooting tools it looked like that is something to have, these chips are not fun to pull being soldered on both sides.
« Last Edit: June 11, 2024, 01:32:55 am by Mick B »
 

Offline MarkL

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Re: 8116A Code 42
« Reply #58 on: June 11, 2024, 02:26:40 pm »
The 547A is handy for troubleshooting this era equipment, and some of these problems in particular, but certainly is not required if you don't get your bid.

For many years all I used was an Edsyn SoldaPullt for desoldering.  Any good solder sucker should pull the solder from both sides.  Sometimes you need to put more solder on for it to be effective, and applying flux can also help.  If there's excessive solder on the top side that's not melting, you could try removing the excess with solder wick first, and then proceed with the solder sucker from the bottom.

I recently purchased a Hakko FR-301 vacuum desoldering tool which does a decent job.  It's much faster when there's a lot of pins.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #59 on: June 11, 2024, 09:16:19 pm »
Hay, the one I bid on someone bought it outright. as I should have. O-well. I have a power vacuum sucker as well as a few manual ones. I just worry about damaging the pads. but it's never stopped me. That tracer looked like such a time saver; I will keep my eye out for a reasonable priced one for the future.
Back to the issue. I followed Pin U37.11 & U39.7
Pin U39.7 has +3.596 and get lost trying to find components do you know what that is in the photo.
What is really needed is a component locater do you have one for option 001? my manual says its located at the end of the chapter but it's not.
I'm going to remove U32 now.
I have U32 on order. nothing local.
« Last Edit: June 11, 2024, 10:35:56 pm by Mick B »
 

Offline MarkL

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Re: 8116A Code 42
« Reply #60 on: June 12, 2024, 03:05:06 pm »
That yellow component is a resistor network.  The "59" next to it means R59, and 1810-0243 is the part number that you can also look up in the parts list.

I never noticed that the Option 001 parts locator was missing from my PDF service manual too.  I have a printed version of the service manual and scanned in that page, attached.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #61 on: June 12, 2024, 06:49:52 pm »
WOW!, thank you for the missing pages, I suspected that was R59 but wasn't sure where R61 was the way the chips jump around. Really helpful. 
  I'm supposed to have the MC10101P ICs by the 17th. I pulled U32 and took voltage readings
U32 EMPTY SOCKET.
U33 CHIP IS STILL IN.
U34 CHIP IS STILL IN.
U37 EMPTY SOCKIT.

U32 Pins
1 & 16 VCC =010.9mv

2(O)    -5.134
4(I)     -2.080
5(O)    -052.12mv

3.(O)     -5.315
6.(O)     -048.63mv
7. (I)     -021.93mv

9.(O)     -1.173
13.(I)    -1.806
15.(O)   -0

10.(I)    -023.44mv
11.(O)   -5.316
14.(O)   -4.515
12.Common Input -5.318


U33 pins
1 & 16 VCC= .014.59mv

4.(I)    -4.380
5.(I)    -5.310
2.(O)   -.752mv

6.(I)    -051.19mv
7.(O)   -4.378
3.(O)   -.772mv

10.(I)   -4.378
11.(I)   -4.517 
14.(O)  -1.771

12.(I)   -1.075
13.(I)   -1.771
  9.(O)  -4.378
15.(O)  -0
8. VEE  -5.314

Pins U34
1 &16. VCC -014.384mv

4.(I)   -4.376
5.(I)   -5.315
2.(O)   -.790mv

6.(I)    -0.475mv
7.(I)    -4.375
3.(O)   -.820mv

10.(I)   -4.375
11.(I)   -5.316
14.(O)  -1.807
 
12.(I)   -1.075
13.(I)   -.778mv
  9.(O)  -1.806
15.(O)  -0
8. VEE  -5.314

Pins U37
1 &16. VCC -013.72mv

4.(I)   -2.091
5.(I)   -2.071
2.(O)  -4.377

6.(I)   -.771mv
7.(I)   -.751mv
3.(O)   -5.311

12.(I)   -1.806
13.(I)   -1.431
15.(O)  -5.317
  9.(O)   -0

10.(I)    -5.315
11.(I)    -2.088
14.(O)   -1.172
8. VEE    -5.315
 
NOTE:   You asked check U39.7. It has +3.596v
And the temp on U33 is 70C Still.



 



 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #62 on: June 12, 2024, 09:37:35 pm »
Notice the voltage on U37.11 @-2.08 there is an intermittent problem also the BUR light. I don't know what the problem is YET but sometimes when turning on, the voltage is missing from pin 11 and not at the same time as the BUR light. I will poke around and see if I can't narrow this down oh ya I can get the voltage up on pin 11 by messing with the mode switch (EBUR)

OK, it seems turning it on when in EBUR mode after being off for a min or so there is no voltage on pin U37.11
Pushing lower left buttons. Pos slope trigger, MAN, 1 Cycle will turn on -2.08v @ pin11 on U37. as well as the EBUR mode button.
I can't get the BUR light to mess up again. :-//
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #63 on: June 20, 2024, 04:51:06 pm »
Good afternoon, The MC10101P (U32) chips have arrived, I have a JBL amp on my bench. I will get back into the HP 8116A tomorrow for those following along. Looking forward to your input Mark.
 

Offline MarkL

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Re: 8116A Code 42
« Reply #64 on: June 21, 2024, 02:36:33 am »
I've been out traveling for the last week.  Will review your latest readings and post some suggestions for next steps in the next day or two...  sorry for the delay.
 

Offline Mick BTopic starter

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Re: 8116A Code 42
« Reply #65 on: June 21, 2024, 10:18:46 pm »
I've been out traveling for the last week.  Will review your latest readings and post some suggestions for next steps in the next day or two...  sorry for the delay.

Hope your journeys went well, Glad your back. I have since removed U33 also, measuring U32 with U33 missing
U32 OUTPUT PINS
  2.  -5.3
  5.  -5.3
  3.  -5.3
  6.  -039.53mv
14.  -5.3
11.  -5.3
15.  -0
  9.  -0.833mv

U32 INPUT PINS
12.  -5.3
  4.  -2.08
  7.  -010.00mv
10.  - 010.67mv
13.  -1.81

U34B PINS
  6. (I) -038 .31mv
  7. (I) -5.07
  3. (O) -0.828mv
 
 


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