Author Topic: Tektronix 2465B oscilloscope teardown  (Read 460532 times)

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Online Howardlong

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Re: Tektronix 2465B oscilloscope teardown
« Reply #475 on: April 05, 2015, 07:07:31 pm »
All,
  My scope is currently fully assembled, so I could not look at the inverter board. However, I did consult my 2445B manual (also covers 2455B) and saw the same component size mismatch as shown in previous posts. I also have a copy of the service manuals for the 2445 and the 2465. Those have the diagrams with the physical size correct, but positioned slightly different. According to all three manuals I have, the parts list C1114 and C1115 as the same value. When looking at the 2445 board layout, the physical size of both C1114 and C1115 are the same, with C1132 being physically smaller. According to what I see in my manuals, C1132 is supposed to be 10uf@160v, C1115 is supposed to be 250uf@20v.

Mitch

It may be that only the "B" versions are affected judging from your layouts.

As stated before, the BOM and schematics are correct. Here are annotated uncorrected and corrected versions of fig 10-13 from service manual 070-6863-01

Uncorrected:


Corrected:
 

Offline malch

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Re: Tektronix 2465B oscilloscope teardown
« Reply #476 on: April 05, 2015, 07:17:55 pm »
Yup that last pic is how my caps are laid out.
 

Offline zze110

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Re: Tektronix 2465B oscilloscope teardown
« Reply #477 on: April 20, 2015, 10:38:25 pm »
So... my 2445 power supply is dead. (Almost identical to 2465).

I went through and replaced all the electrolytic caps... no good.   I made it somewhat through the flowchart but sorta dead ended.

10 > Power Supply Troubleshooting > Audible clicking when power is applied?  YES > Current limit or startup problem > Refer to inverter procedure > Go to 11.

11 > Inverter troubleshooting Procedure > Disconnect Fan > Does supply start? NO > Fuses F1101 and F1102 open NO > Remove comb filter P232 > Connect +5V load to J303 > Does supply start NO >  Remove comb filters P233 and P234> Does supply start? "click click click RF whine from A3 inverter board"  > Check for excessive loading by regulator board shorted pass transistor or regulator IC.


I started measuring some of the resistors on the A2 regulator board.  None seem to meet spec or even close   R1334, R1331, R1332, R1358, R1357, R1354, R1355, R1352, R1353.  Most are between 20 and 70% off of marked value on the parts.  Any idea what is going on here?  How can every part on the board test bad. About 10% of the parts I measured are within 1% and perfect.

Thanks for your help!!
« Last Edit: April 20, 2015, 10:40:58 pm by zze110 »
 

Online Howardlong

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Re: Tektronix 2465B oscilloscope teardown
« Reply #478 on: April 21, 2015, 12:31:16 am »
So just to confirm, with the three combs removed (not the three pin one), running on AC, and a dummy load on the 5V, all comb voltages look reasonable on the inverter board? I assume the whine isn't too loud either, it should be fairly quiet.

I'm not going to be much help on the regulator board, but man do I know that inverter board after finally finding that documentation error!
 

Offline mskobier

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Re: Tektronix 2465B oscilloscope teardown
« Reply #479 on: April 21, 2015, 12:44:41 am »
zze110,

Did you measure all of the voltages on J119 as specified in Table 5-1 on page 5-3 of the manual prior to removing the power supply, and if so, what were the values?

Was the power supply dead, or is it not currently working as a results of the capacitor replacement?

Did you change out the problem prone poly caps?

Did you lift one end of each resistor before you took the resistance measurement? If not, then there is probably nothing wrong with the resistors, and you are seeing more than just the one resistor you were trying to measure. Did all of the resistors measure lower in value than expected? If so, that's probably the reason.


Sorry for all the questions, but it really helps to know what you have or have not done.

Mitch
 

Offline zze110

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Re: Tektronix 2465B oscilloscope teardown
« Reply #480 on: April 21, 2015, 01:01:00 am »
Did you measure all of the voltages on J119 as specified in Table 5-1 on page 5-3 of the manual prior to removing the power supply, and if so, what were the values?
+10V was 0V, +84V was 1.21V... after that I gave up taking measurements.

Was the power supply dead, or is it not currently working as a results of the capacitor replacement?
Identical behavior before and after cap replacement.  It will power up once in 10 tries, the rest of the time I get the 'click click click' and nothing happens

Did you change out the problem prone poly caps?
I replaced them in the high voltage section of the regulator board.  Skipped them on the inverter board. I am getting an lcr meter so I can test the remaining caps.  I don't have another scope so my options are limited to lcr tester and dmm.  I checked the large transistors and they seemed good


Did you lift one end of each resistor before you took the resistance measurement? If not, then there is probably nothing wrong with the resistors, and you are seeing more than just the one resistor you were trying to measure. Did all of the resistors measure lower in value than expected? If so, that's probably the reason.
No, that was dumb I guess.

Sorry for all the questions, but it really helps to know what you have or have not done.
Mitch


Not sure if the voltage was OK or not on the inverter board.  I'm a bit afraid to touch this thing while plugged into the wall.  I pulled all 3 combs and it did the coil whine sound.  Pretty loud to me but I am sensitive to those frequencies.

Tomorrow I am going to replace my EMI filter on the input (leads are in really poor shape) and run the load test again.  Maybe I can get some better measurements this time.
« Last Edit: April 21, 2015, 01:15:45 am by zze110 »
 

Offline mskobier

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Re: Tektronix 2465B oscilloscope teardown
« Reply #481 on: April 21, 2015, 01:20:31 am »
zze110,
   You said you pulled the comb's, but you never said that you hooked up the test load. Did you make up a test load and did you hook it up? The inverter board needs that load for the inverter to start as stated in the manual under the test load diagram. If not try that and see what happens.

Mitch
 

Offline zze110

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Re: Tektronix 2465B oscilloscope teardown
« Reply #482 on: April 21, 2015, 01:28:58 am »
yes, I did connect the test load as specified on the previous page.  I'm going to repeat the whole thing tomorrow.  btw this is a 1xxxxxxxx serial # scope, channel islands built (not sure if that matters in any way).

 

Offline mskobier

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Re: Tektronix 2465B oscilloscope teardown
« Reply #483 on: April 21, 2015, 02:17:34 am »
zze110,
     It should not matter where it was made. I have a 2445B, a 2465 and a 2465CTS. The 2445B works great, and I am working out the bugs on the other two. the 2465 is a B01xxxxx and the 2465CTS is a B02xxxxx, so I am working with a similar vintage to yours. I have a hard copy of the 2445 and 2465 manuals, as well as electronic versions for the 2445B and 2465B series scopes. if you need a scan of anything in particular from the manual, just drop me a PM and I will do what I can.

Mitch
 

Offline zze110

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Re: Tektronix 2465B oscilloscope teardown
« Reply #484 on: April 23, 2015, 11:13:04 pm »
Small update. I set the power supply on my bench (ESD mat 8Mohm to ground) and it started up with all the combs installed.  Observed behavior:

Pulsing fan on startup, very slow to start.  Eventually reached full speed.  Could smell something burning on the board so I looked around a bit...

On the A3 board, R1071 has a nice black burned section through the middle.  I cut the power and measured the resistance, still perfect.
Connect to that is C1072 (one of the caps I replaced).  Slightly warm after 15 seconds but not hot.  According to the PCB marks I have the cap installed the right way around... going to have to check the pcb tomorrow.

R1073 & R1069 test good.  On the part of the schematic right next to those there is a label "+12.6V"  I measured 11.5V but it was bouncing around a lot.

So, tomorrow I guess I will check out the C1072 capacitor.  It isn't shorted and seems to increase in resistance showing it is charging with a meter... and it is installed correctly according to the board.  So something tells me the board has the wrong + mark OR the capacitor is defective and they labeled the wrong lead as negative.
 

Online Howardlong

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Re: Tektronix 2465B oscilloscope teardown
« Reply #485 on: April 23, 2015, 11:51:13 pm »
As I remember, I had a similar concern over that resistor in my scope. Turns out if the supply is not under enough load, it will get quite sweaty, and mine discoloured as a result. Spent a while chasing my tail on that as a result, when in fact all was working. This bit of the circuit is used as a temporary load at startup, and if there's not a load across the supplies this is what takes the hit. The 3.3uF C1072 is quite a high working voltage, 350VDC, I assume you have that?

It's quite a design that inverter board that's for sure!
 

Offline zze110

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Re: Tektronix 2465B oscilloscope teardown
« Reply #486 on: April 24, 2015, 12:23:59 am »
Yes, I replaced C1072 with a panasonic 3.3uF 450VDC.  Having the circuit bake itself isn't what I'd call a good design but oh well...
I'll poke around a bit tomorrow with the 5V dc test load installed.  See if it still starts smoking.  I just need it to work long enough to do the real test  |O
« Last Edit: April 24, 2015, 12:25:46 am by zze110 »
 

Offline zze110

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Re: Tektronix 2465B oscilloscope teardown
« Reply #487 on: April 24, 2015, 11:06:05 pm »
Got the supply working stable with the 5V dc load installed.  Started walking through the regulator troubleshooting guide.

TP201 measurement: 10.00V, perfect.
P232 Pin 1 @ 5V?: No, 5.87V, way out of spec.
Check +5Vd feedback by varying R1292: Feedback working?: No.  I measure -8.7VDC on P233 pin 1 regardless of potentiometer position. -> "Repair path through U1371C and U1040"

Not sure where to look next.  I guess i'll try to look at the circuits surrounding U1371C and U1040 for a bad part.
 

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Re: Tektronix 2465B oscilloscope teardown
« Reply #488 on: May 26, 2015, 02:19:52 am »
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« Last Edit: May 29, 2015, 02:25:55 pm by Simon »
 

Offline Ridgh

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Re: Tektronix 2465B oscilloscope teardown
« Reply #489 on: July 01, 2015, 12:48:37 am »
Hello ALL!
I need - as far as I know - a major help and assistance:
I've bought 2 scopes: 2465A and 2465B. I've tested them prior purchasing for about half an hour and they worked perfect.
After a while, on the 2465B, I've observed that the trace and readout are dimming after approx. half hour up to disappearing completely. I found a friend that told me to change the capacitors on PSU and I did it.
The new capacitors are on specs, but maybe it was mentioned on this forum that 2 capacitors are interchanged on Layout. After this "incident", I got no trace or readout.
The 'scope does several tests (the 4 channels, and at ADD it remains stuck. After pressing A/B Trig, the panel lamps are working and responding, there are "clicks" when they should be (compared to the A version, but nothing appears on CRT. Just after several hours it is disconnected (5-24 hours), the beam appeared, without readout.
I understood that A5 PCB has a problem, and indeed I've found several leakages from electrolytic caps. There was a lot of "salt" on the solder, and as well a 10k resistor (0.1%) burnt. I exchange then with what I had on my lab and ordered new ones that are supposed to arrive within 2-3 days. All the voltages at J119 are good. The DAC shows me that I have inputs as they should be, the microprocessor pin 40 is high (it should be), and I have a good stable clock at pin 39. The DAC has normal measurements at pin 16 and 19.
The U800 is not too hot (approx. 50*C after 20 minutes).
These are the details so far. From time to time, (long time...) the 'scope has a beam, but it surf down the screen up to ~70%. It can be moved up or down, right and left. However, if I turn it off even for a second, I can see nothing again on screen.
The recall button works, I can recall the saved configurations. The beam finder doesn't work.
I'll be more than thankful if any of the members from this forum may help or get an idea for what I am supposed to look for further.
This is the summary, and I have no idea  what to do further...
Thanks in advance,
Ridgh 
« Last Edit: July 01, 2015, 12:52:18 am by Ridgh »
 

Offline MarkL

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Re: Tektronix 2465B oscilloscope teardown
« Reply #490 on: July 15, 2015, 05:46:55 pm »
I have a printed copy of the "2445/2465 Option 06 and Option 09 Counter/Timer/Trigger and Word Recognizer Service Manual", pub #070-4632-00, so I can say the service manual is not the same.
Dredging up this old thread...

I've had several requests for this manual since the 2445/2465 (plain version) CTT WR service manual doesn't seem to be out there anywhere.  I've scanned in my copy and you can pick it up here if you're interested (no index or OCR):

  http://employees.org/~markl/Tektronix_2445_2465_Opt_06_09_CTT_WR_Service.pdf

I've also uploaded it to http://www.ko4bb.com.  I will delete the above copy once KO4BB publishes it.
 

Offline SoundTech-LG

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Re: Tektronix 2465B oscilloscope teardown
« Reply #491 on: July 19, 2015, 11:27:40 pm »
Speaking of CTT...

I just now finally solved this on 2467B/2465B.

I got a CTT 87 error 78 message after having the TV/CTT option board out of my scope.
I swapped it with another board from another scope. Now both scopes had the same CTT error message.
I have been pulling hair trying to figure out what I blew up/ESD etc.

Nope... just hidden under the J101/J102 cables for the options board is another connector that connects to J104. :palm: In the case of TV options, it also connects to  J100, J103, J105, J109, but the error is generated off J104 not being connected.
You can't see this connection to the bottom edge of the option board, unless you peer down under the cables going through the main board hole!!!

Quite relieved to find this. Been playing around with this for months!
Something to be aware of if you remove the CTT or TV options board on 2465B's or 2467B's.
« Last Edit: July 19, 2015, 11:31:02 pm by SoundTech-LG »
 

Offline SoundTech-LG

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Re: Tektronix 2465B oscilloscope teardown
« Reply #492 on: July 27, 2015, 06:23:30 pm »
Did the CRT replacement on one of the 2467B's. Pretty straightforward. Just be careful with the neck terminals. Quite fragile. Attaching the wires back on to the neck required a small flashlight. Hard to see in there at the mainboard. Threading the cables through the shield holes is critical for lead length, so take note as you remove them. I was able to find the CRT on ebay, which is a miracle in itself, but the fact that NO SCREEN BURNS was 100% true, was amazing. the original CRT had some, not real bad at all, very usable, and only noticeable under a full screen flooding. So now I have that one as a spare, just in case...
 

Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #493 on: August 11, 2015, 10:23:54 am »
Hey guys, I got a 2465B (>B04xxx serial) back in January to fix up. I had taken it apart, cleaned it, checked caps, swapped the BBSRAM, etc.

Unfortunately, I had a bunch of other pressing projects come up so I didn't get the scope back together until last week. At least, it *seems* back together... I've got a mystery part that, for the life of me, I can't figure out where it goes. I've checked the exploded diagrams in the service manual with no luck.

Any ideas?






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Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #494 on: August 11, 2015, 11:04:46 am »
Annnnd nevermind. I found it in the 2465A Options Service manual, of all places...





Oh, if anyone needs knobs, buttons or a replacement front panel board, let me know. The overlay on my unit was trashed and I scored a deal on an entire front panel assembly, so I've got parts!







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Offline SoundTech-LG

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Re: Tektronix 2465B oscilloscope teardown
« Reply #495 on: August 11, 2015, 07:34:01 pm »
knobs, shaft extenders, and pots. How much???
 

Offline timb

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Tektronix 2465B oscilloscope teardown
« Reply #496 on: August 12, 2015, 09:11:42 pm »
knobs, shaft extenders, and pots. How much???

Send me a PM and we'll figure out something. Do you want the entire board, or just the pots? (The board 100% works and has been fully cleaned with DeoxIT.)


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Offline SoundTech-LG

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Re: Tektronix 2465B oscilloscope teardown
« Reply #497 on: August 13, 2015, 04:31:08 pm »
Sent the PM. not seeing responses... :-/O
 

Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #498 on: August 14, 2015, 12:16:29 am »
Sorry, I've been tied up all day.  I'll get to it this evening! :)


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Offline timb

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Tektronix 2465B oscilloscope teardown
« Reply #499 on: August 14, 2015, 09:46:48 am »
Sent the PM. not seeing responses... :-/O

Replied!

In other news, I got my 2465B back together tonight and it lives! Originally, I had put it back together on Saturday, but when I turned it on all I got was a flashing TRIG'D light. Turns out I had put the A20 (buffer board) ROM in backwards... Doh! Of course it was fried. Luckily, I had a dump of it! (Which was the entire reason it was taken out in the first place.)

Ordered some NOS M2732A's with a 1998 date code from a US seller that got here today. Programmed one, popped it in and everything seems to work! Hurray!

My unit is a 2465B-CT with a Pre-B049999 serial. I replaced the SRAM with FRAM, which works fine. Unfortunately I lost the cal data when trying to read the SRAM with my programmer while simultaneously keeping it powered. (These low serial units used a discrete battery and SRAM chip.)

Another issue I noticed is an error 06 02, which relates to the battery voltage. Obviously, since there's no battery installed there can't be any voltage to detect! The fix ended up being pretty easy:

Remove CR2770 and replace it with a 4.7K resistor, then add a jumper wire across the former battery + and - pads. The negative battery pad goes through a 10K resistor to ground; CR2770 connects the positive battery pad to the SRAM's VCC line.

Without the diode, +5VD flows through the new 4.7K resistor, which together with the existing 10K unit create a voltage divider. This feeds about 3.4V into the battery voltage detection op-amp.

Here's before and after schematics:


Before


After


The Mod

No more error 05 on startup! (I am getting CT TEST 81 FAIL 02 and 86 FAIL 02, but after having a look at the options service manual, these are related to calibration.)

Now, to figure out what I need to calibrate the unit...


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