agilent 54845A project ( REOPENED )

[charlyd]

Hi TRN THX.!! that would be very helpfull, maybe a good idea to see how the test outputs it self with a Hybrid off.  so NOT SEEN for the unit. When you run the logging maybe some puzzle pieces fall into place.

[TRN]

I removed Hybrid#1, ran the Self Test, and measured all the DC voltages at the Hybrid socket.

The attached PDF shows the self test results. The XLS sheet shows the DC values measured.

rgds

[charlyd]

@TRN:  you did great work. Which was your reference point? one of the GND pins??   First thing when i am in the workbench i gonna check it.

today i took my all 4 hybrids off so there is no heat problem. for this moment i want to figure out where my trigger signal is...
 

[TRN]

Yes all voltages reference GND.

[charlyd]

this is with the attentuator on? 

[TRN]

Yes,

Both attentuators installed; only Hybrid #1 removed

[charlyd]

Hello everbody maybe it is good idea because there is not much info known about the acquisition boards. to collect all REVERSIONS of the board with the Original problem.

username            VIN#           AcQ reversion     Mobo version      problem
charlyd                033             Rev. C                VA-503              Fine Interpolator Handshake error; service required

[Ashevil78]

Hello there I'm new to this blog I have a agilent 54845a myself
The scope it self works perfectly all on board tests pass with no failures as well as on boot up no failures also
I changed the cmos battery because it was dead
The only issue I have is when I start it up for the first time after being shut off for awhile it hangs in the windows boot up .
So it usually takes about 3 or 4 power cycles to get it to boot completely once its booted it runs perfectly .
Is there anything on the windows side that would cause this issue or maybe the ram is causing this .
Any help would be great thanks
Bill

[charlyd]

i saw in some topics and even on the keysight website that reinstalll the unit sometimes does magic...as a quick win i will try that first ..

:edit:  re-install did not help me. on first reboot i got a calibration message, for a short while i hope to have fixed it.
          But after the second reboot the error was back visible.

[charlyd]

ok did a deep dive on component level.


The interpolator is a circuit designed to measure the time from the input signal initiated trigger event to the next edge of the timebase post trigger delay clock. To measure the time interval, a capacitor will be charged rapidly through a constant current source. The charge on the capacitor will be  directly proportional to the time interval during which the constant current is applied. The capacitor is then discharged through a stretcher circuit consisting of a constant current source which may be as much as one thousand times smaller than the constant current source used to charge the capacitor. Two voltage ramps are observed, a charging ramp and a discharge ramp. The discharge ramp is used to gate a counter on at start of the ramp and off at the end of the ramp. While gated on, the counter counts clocks of a known clock width to measure the time of the discharge ramp. If the ratio between the charge and discharge constant current sources is known then the time between the trigger event and first delay time post trigger delay clock can be calculated. The test of the interpolator circuit is a re-run of the calibration software for the interpolator. There are two time intervals measured in the interpolator calibration. A short interval of two periods of a known clock and a long interval of three periods of the same clock.  The difference between the two time intervals will be an accurate measure of the clock period since fixed system errors will cancel out.

Getting you started

Error Symptom   Diagnosis   
Interpolator Self Test fails   Look for evidence of short and long ramps.  Probe at base or emitter of Q36 or around zener diode VR1
Check ramp control                        U127A pin 3   (MC 10H131)
Check set line of D-flip flop             U127A pin 7   (MC 10H131)
Check start interp cal line               U128C pin 17 (MC 10H116)
Check interp cal control line            U116A pin 8   (MC 10H131)
Check interp cal width control line   U124   pin 13 (MC 10H105)

i probe arround Q36 (smd code : 1AM)  and VR1  (smd code : Z11)

can somebode help me out telling me what voltage is on the emitter and base in a good working 54845A.

(Q36 is located on the topside in the corner where the flatcable from the computer card is connected to the AQ board.)

[charlyd]

today i went into the faults again  i have 3 failed situations in my tests so i decided to drill down into there to see if there is a common component.

[charlyd]

;EDITTED:

i think i am in the need of some dump parts.   Who can help me out with a hybrid

please PM me if you have parts like a hybrid 1NB7-8348 or the mylar flat cable which goes to the input panel.
[ this message is not relevant anymore]

[free_electron]

i may have that flatcable. i need to delve in my parts bin.
i don't have donor boards for the 845.

the fact that you have so many errors leads me to believe you have a bigger isssue.
your relay clicks for example are nonsense. which leads me to believe the calibration ram is corrupted or empty.

take that cr2450 battery off the scope adapter card and install a fresh one. then attempt to run the self calibration. that will reset the cal ram.

[charlyd]

@free_electron: hello thanks for you reply i for sure keep the flat cable in mind but first fix...but does the battery create a "Fine Interpolator Handshake error" ? did you even see that error with the solution of the battery. my batterij measures ok if i am right.  but will check as soon as i am at work.

pitty no donor board. so my question stays open

Who can help me with a donor board?

[free_electron]

if the calibration ram gets corrupted there is no telling what the machine will do. it may load wrong constants.
disconnecting that battery and reconnecting will erase the ram. the scope will detect that and load factory defaults and then ask to perform a calibration. this will bring the machine to a known state.

[charlyd]

meanwhile i arrived at component level U133 there should be some clocks…-> no clocks at all...U133 is a Actel A1010B PL44C FPGA.  thats why i was looking for a donor part board.

also discovered [closeup pictures are taking under a microscope]dirty solder work arround the U121 (pins 19 and 20 were shorted) and on some neighbour chip also dirty solder work, chips like U120 & U133 ..  Somebody must have been in a terrible haste !

Or was it a matter of "shotgun trouble shooting" at the service centre?

[charlyd]

@free_electron: i tried the battery trick from the pci-card without any succes.

so i decided to probe arround for a while again last night. My conclusion for now: i miss the clock on U133 so the U130[SC64031FN] is next to look at the so called clock manager.

i can t find any datasheet from this guy SC64031FN  so datasheet wanted / donor chip wanted    [parked for now]

Interpolator error says:  U127  [check pin 3 and 7] but what about the power supply on this chip it has as power pins  1,16 & 8  what should they be? 

one of the pins show -1.8v  (measured to GND) i would say not ok.

the 100Mhz crystal on the other corner/side of the board is checked and ok.

[TRN]

charlyd, the pinout from the datasheet of U127 is for a 16-DIL package. Pinouts for 20-PLLC are different.

See the attached conversion sheet.
So pinout is as follows:

VCC1 = pin 2 =0VDC
VCC2=  pin 20 =0VDC
VEE = pin 10 = -5.1VDC

I measured the  following voltages over VR1:

Between Kathode & Anode: 2.45VDC
Between Kathode and ground: 2.92VDC

[charlyd]

Ah this is a good point special thanks to @TRN for the conversion sheet. Apart from i was missing the pins of course nothing was written in my datasheets....but this makes sense

an update is on its way, and also about the other power supplies and on the pins in that area ….

[charlyd]

After spending hours searching for something to holdon. i took the attachments again and looked for a general thing..
Let s see if there is a steady 100Mhz  on the PLCC chips and on U130 pin 2 it should give a 100Mhz in. Probing arround with the Tektronix i discovered the 100Mhz is not like it should be. sometimes visible sometimes not.

100Mhz were does that come from..

Ok looking for crystal Oscillators on the board i found 100Mhz were does that come from.. I found a 2 Oscillators a big Vectron 2Ghz en NEL HS2810. - 100Mhz on the otherside of the board. checked over and over again and then went to "the NEL HS2810 corner" is this Crystal failing from time to time.. or more failing then working.
i decided to take it out and build a test circuit. it is a negative powered Oscillator so -5.1v is powered.  see picture.

and i didn t get any output...

 

[charlyd]

For my feeling the NEL is not ok.   

A few things kept spinning in my mind and bringing the 100Mhz from one side of the board to the complete otherside is really weird.
The U121 with the shorted pin 19, 20 from dirty solder work made way back in time before i got the unit. 
and some not responding PLCC chips. Let find the datasheet from the big vectron 2Ghz Oscillator. 
mmmm difficult to find a datasheet from this bigboy but i found something what cleared things for me..
this is a Double Crystal Oscillator  pin A = 100Mhz and  pin B = 2Ghz and this one is located next to the PLCC chips. so i pulled the bigboy and
it is powered with +15v to GND. see picture.

i took the Double Crystal Oscillator out and after feeding 15 volt i got nothing out.. on this one also..

this is really strange a failed Double Crystal Oscillator. If that is the case where does the pin A (100Mhz)  lead to.

Exactly to the U121, the 10H116 with the dirty solder work so it looks like the Double Crystal Oscillator has been shorted for a longer time and died??

the Double Crystal Oscillator is on its way.  together with a 10H116.

   
 

[charlyd]

on the bottomside in the neighbourhood of the NEL HS2810 there is a 14 pin ACT14 ( 74ACT14 - 6 Hex Schmitt-Triggered Inverters)
they also past this chip a while back with the "Art of soldering" i checked it, it was ok but it needed resoldering to be fitted good.

so now it is waiting for the parts…… and the NEL HS2810 is added to list of wanted parts from a donor board.

@tony_g   you were right this unit was a MULE.

[charlyd]

some weeks past before the parts arrived.. I replaced the U121 and the 100Mhz osc. and when powering on i fell into the next problem…. 
the LCD went white after moving the Long white flat cable a bit the picture was back and gone..  so that cable needs also be to replaced but no problem…

let s connect a External monitor and yes the picture was there...ok now fingers crossed and boot the Mule.

after booting i got a message like needs calibration …..my "Fine Interpolator handshake failed: Service is required". was gone.. so that is a real positive step forward..! but i still have all 4 my ADC of the board and my both Attentuators are also not connected.. so no triggered signal..
ok let first find the flat cables which i need so my LCD is also working again. and then easy build the mule together with one channel.. ans see what happens.

 

[dzseki]

Sligthly off topic, but I was just reading the October 1993 issue of the HP Journal, where they go into detail with the interpolator of the HP 54720 from page 24, which is of course a different model than yours, but I believe they are based on the same concept, they also give specs on the 2GHz oscillator, although it might be a different model, but sure looks similar enough. It should be a good read for those who are interested in the art.

[charlyd]

so today i spended an other day again at the 54845A project.

i decided to have a look at the display to see if there is the reson from my flickering LCD and yes ...1 very small connector was not connected on the LCD side. So pulled apart the front and see if it is fixable...ah reconnect and see if the LCD is working.  Yes strange but ok.. fixed.

Time to build the mule back together.. and see what happens with the selftest and when that shows many "PASSED" i can go on to the Calibration part and see what is happening there. 

i decided to put all Hybrids back in and then bring it to life…

so after a while when the mule looked a bit like a scope again...it is time for power on and selftest.  I long while ago i already decided to disconnect the Original harddrive because i don t want to damage or delete usefull history data.

So already on het start of this project i took a 20GB maxtor drive and restored the 4.3 software version using a extra CDROM drive connected to the second IDE port from the VA-503A which i needed to load bios defaults to get the second IDE back to life again. Ater that i restored like the procedure explained howto reinstall the scope.  with the #VIN033 first restore was software version 4.3 and then upgrade to version 4.5. so i ended up with a new installed drive leaving the Original in tact.

after booting i got the calibration needed message .. and as i told 2 posts back my error was definitely gone.  i connected a keyboard and mouse and now it is time for the selftest… with all hybrids reinstalled again…

after powering on first thing i saw was i got 3 good triggered signals ch2/ch3/ch4  and my channel 1 trigger signal was gone..   
next step "the selftest"...
A to D convertor and FISO error.  all errors were in the first few tests and somewhere a warning that the Attentuators contacts were totally out limited…Attentuators needs to be replaced...

of course why should the mule would work already in one time. of course not...