EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: Zucca on November 24, 2019, 09:13:36 pm
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The previous owner did not care too much, he deserve a middle finger >:( ...
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=81471.0;attach=868682;image)
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=81471.0;attach=868248;image)
I want to save this sick device!
What I did:
1) Replaces all leaking and not caps. Yeah they did leak but not soo much... board cleaned and it was not corroded.
2) Fan replaced (just becaused it was cheap)
3) the poor tortured U629 was replaced with a new one and put back in the original location.
4) The missing R100 was installed with a similar model... the cement one was too expensive.
5) Zip tied the big blue capacitor C611 15000µF closed to U629
Now I got the following errors:
404.1 – Absolute value (x1 gain); -full-scale DAC output
404.2 – Absolute value (x1 gain); -half scale DAC output
404.3 – Absolute value (x1 gain); zero DAC output
404.4 – Absolute value (x1 gain); +half-scale DAC output
404.5 – Absolute value (x1 gain); +full-scale DAC output
405.2 – Absolute value x10 gain comparison; large +DAC output
405.4 – Absolute value x10 gain comparison; small +DAC output
406.6 – Voltage comparison
407.1 – Front end; 2V range
407.2 – Front end; 200V range
407.3 – Front end; 750V range
412.1 – AC amps switch
This is just the first post, now I will start the investigation.
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Power supply check ok. The only thing somehow strange was
U103, pin 3: 22,3V (~+18V in the manual)
U103, pin 2: 7,89V (+8V in the manual)
but I will not consider it as a defect.
Now with the unit warmed up I got these errors as well in addition to the others before:
405.6 – Absolute value x10 gain comparison; small –DAC output
405.8 – Absolute value x10 gain comparison; large –DAC output
410.1 – True RMS converter
411.1 – Filter; true RMS
411.2 – Filter; true RMS
:horse:
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Check booster power stage and stuff around dual JFETs U5** , if my memory still serve me well.
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Did you recap all the electrolytics ?
Better do it before you really get a mess.
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Did you recap all the electrolytics ?
Better do it before you really get a mess.
oh yes read above point 1).
What I did:
1) Replaces all leaking and not caps. Yeah they did leak but not soo much... board cleaned and it was not corroded.
I opened up the unit and fond some elco pee, it just started leacking.
I did not power up the unit and replaced and cleaned everything like a good EE boy.
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https://xdevs.com/fix/kei2001/ (https://xdevs.com/fix/kei2001/)
https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/ (https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/)
Did some homework with the excellent TiN article and previous posts:
If you have many 4xx.x series errors check U520 and U525. These op-amps have floating power and can be damaged from bad capacitors in doubled voltage supply.
[...]
Many 4xx.x tests we failing in self-diagnostics.
After few days of troubleshooting culprit was found in Linear Systems U441 dual JFET pair in floating FE circuitry, causing current mirror to become unleveled and failing all related tests and operation. U520 had incorrect drive due to one of JFETs in Q512 gone bad.
will check it.
Desolder U507, U508, U509 and clean surface/pads in this area with clean acetone. After cleaning – solder U507,U509 back, and replace U508 to new 74LS00 as it’s just jellybean part and easier to put new in, than testing if original is ok.
Mine were in contamination for about 12-14 hours, I cleaned them well and they look good... I pospone this.
https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg727146/#msg727146 (https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg727146/#msg727146)
The failed component was Q547 - it wasn't totally open but but didn't turn on properly so relay K503 never closed.
https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg762210/#msg762210 (https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg762210/#msg762210)
Q518 was shot, IMHO because K503 was stuck closed before.
will check
PS: If you need the Service stuff, look here:
https://cal.equipment/doc/Keithley/2001M/CDROM/Model%202001%20Repair%20Manuals/ (https://cal.equipment/doc/Keithley/2001M/CDROM/Model%202001%20Repair%20Manuals/)
at https://xdevs.com/ (https://xdevs.com/) the links do not work anymore.
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TO DO List after repair:
1) New Front Panel (Assembly or not?)
2) Missing Bolt at rear coax input, those are important to keep the analog board in place. where I can find them with washer?
3) MEM2 update with DS1245Y or for the future:
https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg956554/#msg956554 (https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg956554/#msg956554)
4) FW Upgrade
OPTIONAL
1) µV Meter option
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I got stuck with an ADC selftest error while the meter itself works flawlessly.
The problem is probably somewhere a single corroded pcb trace perhaps inside layer that is high ohmish.
The ADC draws current during selftest and then the voltage drops.
Can not find the culprit, I like Keithley very much but the way they overcrowded this pcb with its tiny electrolytes stuffed against the very hot voltage regulators made me rethink if I like them really that much.
So lessons learned, really spent time to see if the traces are clean and you don't have any corrosion inside the pcb.
I do hope your patient on your table is in better condition than mine and you will get it to work 100% :)
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I got stuck with an ADC selftest error while the meter itself works flawlessly.
The problem is probably somewhere a single corroded pcb trace perhaps inside layer that is high ohmish.
The ADC draws current during selftest and then the voltage drops.
Can not find the culprit, I like Keithley very much but the way they overcrowded this pcb with its tiny electrolytes stuffed against the very hot voltage regulators made me rethink if I like them really that much.
So lessons learned, really spent time to see if the traces are clean and you don't have any corrosion inside the pcb.
I do hope your patient on your table is in better condition than mine and you will get it to work 100% :)
Put it on the bench again, we will fix it together.
Yes the Keithely EE did some sloppy job somewhere in the K2001. That's why the EEVblog EE are here to help.
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Put it on the bench again, we will fix it together.
Yes the Keithely EE did some sloppy job somewhere in the K2001. That's why the EEVblog EE are here to help.
:) I have my patient put in another EE hospital with a doctor that has about 20 years more repair and faultfinding experience than I do 8)
He has it as a pet project spending a few hours here and there.
The nice thing about the Keithleys is that the service manuals and schematics are often available, perhaps not 100% complete but still thanks to TiN for a larger part.
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Test 400.1 – DAC; -4.21V output
The TRIG bits for OUT B of the DAC (U531) are programmed to produce -4.21V at PRECOM+
(pin 1 of U528). This signal is routed through R560 and U532 (DAC line pulled
low). This line, now called ACF, is selected by multiplexer U511. The output (OUT) of
the multiplexer is routed through buffer U342 and resistor R223 (where the line is
called ACV/A). The signal on ACV/A is then routed through U320 (/AC pulled low)
and applied to Op Amp U322. Measure -4.21v at A/D IN.
this passes.
This 404.1 fails:
Test 404.1 – Absolute value (x1 gain); -full-scale DAC output
DAC U531 is programmed to generate -4.21 VDC at PRECOMP+. That signal is then
applied to ACF through R560 and U532 (DAC line pulled low). ACF is routed to AMP
IN via U526, Q516, and the AC input buffer.
AMP IN is tied to the inverting and non-inverting paths of the variable gain ampliÞer
(VGA). NETOUT (output of U519) is routed to the Zero-Crossing AmpliÞer which,
based on the polarity, generates the appropriate COMP- signal that is applied to comparator
U507. The comparator selects the path that the AMP IN signal will follow
through the VGA by closing the appropriate analog switches of U509.
The negative (inverting) AMP IN path is through R530, U515, U509, Q501, and U516 to
pin 12 of the multiplexer (U511). The output (OUT) of the multiplexer is routed
through buffer U342 to ACV/A. The signal on ACV/A is switched through U320 (/AC
pulled low) to the A/D buffer (U322) which is conÞgured for x1 gain. Measure +4.21V
at A/D IN.
the circle is getting smaller.
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U509 is mentioned in all the failing tests and only there.
We have a high suspect component.
Next move is to listen to TiN advise and
Desolder U507, U508, U509 and clean surface/pads in this area with clean acetone.
:popcorn:
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But do you use acetone or IPA, I am afraid that acetone could remove the silkscreen ?
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IPA should be enough... silkscreen ist partially already gone.. do not care too much.
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Under U507, U508, U509 there was some junk and I cleaned everything up.
Unfortunately nothing changed.
Time to dig more into the problem.
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IPA should be enough... silkscreen ist partially already gone.. do not care too much.
For cleaning things like leaking electrolyte water may be a better solvent than IPA. So it can be a good ideal to start with water or at least a water IPA mixture. Pure IPA or methanol would be than the last step.
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Thanks Kleinstein, I did wash the chips with IPA and water. On the boardI used IPA to remove the tacky flux and whatever was there. At the end it looked very clean.
Anyway tonight one step back.... maybe.
I powered off the unit to look for a good A ground with a 34461A so I could poke around for the signals...
Guess what... I powered the unit back and got these new errors:
400.1, 2, 4, 5
and they stayed there no matter what I did.
So back to the schematics and here what I found while running 400.1 (schematic 2001-902-06.pdf page 4)
[attachimg=1 width=400]
R560 is connected correctly and I measure 10KOhm betweem PRECOMP+ and U532 pin2.
There is too much current flowing through R560 causing the big voltage drop.
Are those DG411 and DG211 started to leak right now?
Time to listed to plesa:
https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg1064632/#msg1064632 (https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg1064632/#msg1064632)
I propose replace shift registers 14094 and all analog switches (DG411/DG404/DG211). It is much faster than troubleshooting these failures.
(http://www.runkarlarun.com/wp-content/uploads/2012/12/alice-falling-down-rabbit-hole.jpg)
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OPTIONAL
1) µV Meter option
Only if your meter has B-type firmware (2 ROMs) and you don't mind spending $1K+ for amplifier setup.
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Only if your meter has B-type firmware (2 ROMs) and you don't mind spending $1K+ for amplifier setup.
B-type 2 (ROMs) is there. That said I am very happy it's just an option for me, I do not really need a µV.
Anyway much cheaper than many others µVmeters out there.
Thanks you again TiN for all your effort to document your fixings.
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Coming next...
IC, CMOS ANAL. SWITCH, DG411DY(SOIC)
VISHAY DG-411DY-E3
U317
U522
2 Qty
IC,CMOS ANALOG SWITCH DG211DY(SOIC)
VISHAY DG211BDY-E3
U510,U515,532
U318-320,323
7 Qty
and if they are in stock and cheap:
IC, CMOS ANAL SWITCH, DG444DY, (SOIC)
VISHAY DG444DY-T1-E3
U526
1 Qty
IC, 8 STAGE SHIFT/STORE,MC14094BD(SOIC)
ON SEMI MC14094BDR2G
U500,501,505,530
U800,801
U300,302,303,305,307
11 Qty
IC, MCHAN LAT DMOS QUAD FET, SD5400CY (SOIC)
Unknow in Manual
U509
1 Qty
IC, QUAD 2-INPUT NAND, 74HC00M (SOIC)
Unknow in Manual
U508,513,536
3 Qty
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DG411 can be upgraded to:
https://www.mouser.de/datasheet/2/256/maxim%20integrated%20products_dg411-dg413-1178575.pdf (https://www.mouser.de/datasheet/2/256/maxim%20integrated%20products_dg411-dg413-1178575.pdf)
same with DG444
https://datasheets.maximintegrated.com/en/ds/DG444-DG445.pdf (https://datasheets.maximintegrated.com/en/ds/DG444-DG445.pdf)
Bonus: same with DG408
https://datasheets.maximintegrated.com/en/ds/DG408-DG409.pdf (https://datasheets.maximintegrated.com/en/ds/DG408-DG409.pdf)
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Those old CMOS switches somehow seem to be prone to failure.
Not many of the switches are really critical and need very low leakage or resistance matching.
The new chips are usually DG2xxB and thus already an upgrade to the old version without the B.
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Those old CMOS switches somehow seem to be prone to failure.
Not many of the switches are really critical and need very low leakage or resistance matching.
The new chips are usually DG2xxB and thus already an upgrade to the old version without the B.
Correct but I could not find the B version of DG411, DG444, DG408 and I went to Maxim.
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[attachimg=1]
if nobody has a better plan I will order tonight.
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For the switches in the AC part, I would be careful with an "upgrade", as for these switches the capacitance can be more important than leakage. So changing the switches would likely need a new low level Cal / adjustment for the AC part.
Also many of the other switches are not with high impedance parts and not that critical. So no need for the more expensive Maxim parts. It looks like the really critical signals are switched with JFETs anyway.
AFIAK most of the DG4xx are new chips and thus no separate old and B version.
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Thanks Kleinstein to stay with me in this madness.
I am planning to re-calibrate the unit at the end anyway also to have the certanty it works properly.
Moreover this device with full schematics makes a lot of fun and I want play a little bit with it.. so it's more a learning experience than a proper fix it and forget it project. That's also the reason why I keept this 20 years old DMM and not turned in a DMM6500 or so.
If someone have some idea to try it out just let me know.
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Order placed.
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All right, Digikey delivered.
One minor step forward tonight.
Replaced U522, U532. Nothing changed.
Well not so fast.
Everytime after de- or soldering a chip, always power on the unit to check if and where something changed.
I traced the problem at U526 (the next after U532 in the signal path).
Replaced U526 and bingo the 400.x Problem went away.
Now I got:
402.1
404.1-5
405.2, 4 ,6 ,8
406.6
407.2-3
412.1
before was
400.1, 2, 4, 5
404.1-5
405.2, 4, 6, 8
406.6
407.1-3
410.1
411.1-2
412.1
I could be more happy that I bough all the DGxxx chips.
The plan is to get the unit error free again and then replace all the chips with new ones.
It takes time but it is fun.
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oh oh..
402.1
OUT B of the DAC (U531) is set up to output 4.33V at PRECOMP+ (U528 pin 1). The
operation of the frequency switch, U522 (FREQ pulled low), is veriÞed by dividing the
PRECOMP+ voltage by the voltage ratio across R560 and R558. The "on" resistance
(approximately 25Ω) of the analog switch (U522) is added to the resistance of R558
since it is part of the ratio. Again, as in the 400 series tests, this voltage is routed to the
A/D buffer (U322) which is conÞgured for x1 gain. Measure 32mV at A/D IN.
my new fancy improved U522 has a Ron of 3Ω max.... :horse:
Tempted to replace R588 with a 75Ω to compensate >:D
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404.1 on hold, I start to suspect the U509 (IC, MCHAN LAT DMOS QUAD FET, SD5400CY (SOIC)) is gone... :popcorn:
[attachimg=1]
U508 and U515 were replaced with brand new ones....
:horse:
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Two SD5400CY are on the way to me. I paid them 9€ incl. shipping :horse:
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Darn looks like your 2001 was a zombie.
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This is a painful fun, the worse it is the more happy you will be at the end.
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Check and doublecheck internal pcb trace corrosion when the ics are removed with a bright led lamp below it. ;)
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Check and doublecheck internal pcb trace corrosion when the ics are removed with a bright led lamp below it. ;)
Generally yes, in my case the leacking damage was very little on the surface, so I don't think it will help.
What is mandatory is to check if the same voltage is on the pins connected togheter, and if there is something not OK power down the unit and check the traces resistance with a DMM.
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Desoldered Q501, between D and S 1,2KOhm with nothing on the gate.
:horse:
Maybe I did/do not need a new SD5400CY, oh well...
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For testing the MOSFETs, one should use a defined signal at the gate, more like gate connected to source and substrate: should give high impedance.
Testing with an open CMOS gate is like a random number generator.
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R gate to source = R gate to drain = 1,03 MOhm
I don't like it.
Moreover I tried to put a negative square wave at the gate and I did not get nothing on the drain out (yes with a 1K pull up resistor to 10V).
Then I applied -10V=Vgs and the R between drain(+) and source was -2,1MOhm, between source(+) and drain was 30MOhm... :scared:
With Vgs=0V (gate shorted to source), Rdrain-source 135Ohm.
To me it's dead.
And of course the SST4416 JFET is obsolete.
https://eu.mouser.com/datasheet/2/427/910019-1211380.pdf (https://eu.mouser.com/datasheet/2/427/910019-1211380.pdf)
:horse:
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MMBFJ112?
https://www.onsemi.com/pub/Collateral/MMBFJ113-D.PDF (https://www.onsemi.com/pub/Collateral/MMBFJ113-D.PDF)
I go in bed, see ya.... :=\
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New SD5400CY arrived today, replaced.
Ah I resolder the q501 back.
Now I get:
402.1
404.1 ,2
405.6 ,8
before it was:
402.1
404.1-5
405.2, 4 ,6 ,8
406.6
407.2-3
412.1
(http://mullans.me.uk/wp-content/uploads/2017/07/893714.png)
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Power down and up again.
Now I got:
402.1
404.4, 5
405.2, 4
407.1, 2, 3
412.1
:horse:
ar the third time power up:
402.1
404.4, 5
405.2, 4
407.1, 2, 3
412.1
looks stable now.
mmmm the temperature is playing a role here?
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xxx4416 FETs of some kind should still be available, possibly in a SOT23 case.
AFAIK J112/J113 are essentially the same as the usual 4391/4392 JFETs typical used as switches.
Getting JFETs is becoming tricky if a TO92 / TO18 case is needed. The same chip in SOT23 is usually still available.
There are quite a lot of similar FETs from the same process, but different testing sold under different numbers.
A good reference for JFET data / replacements can be Fairchild AN6609.
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Kleinstein Thanks you so much, one day you need to tell me why you know everything about EE componets.
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Well power it up today, here what I got:
402.1
404.1, 2
405.6, 8
I tried to let it warm it up, turn it off and on again but it did not moved from there.
Is my bench slowly repairing the devices just by holding them against gravity?
No sense, or I have an intermittent contact somewhere. :-//
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Today's errors:
402.1
404.4, 5
405.2, 4
407.1, 2, 3
412.1
:horse:
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Different errors coming up could be a parameter that is just boarder-line. Something like a intermittent error (e.g. cold solder joint) is also possible.
The 40x self tests are testing mainly the AC part.
The service manual describes the test in quite some detail and AFAIK one can run them one at a time to bring the meter in a defined state.
A point to check would be the DAC to generate test signals. Also have an eye on some of the CMOS switches - some of the old DG2xx tend to fail with age.
Besides the build in tests one could also create a test case by hand: measure some AC voltage and follow the signal to the RMS converter.
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Thanks Kleinstein, always a pleasure to read your comments.
Now I know what is going on.
The problem (thank God!) is the zero crossing amplifier, The input signal NETOUT is correct but the output signal COMP- goes bananas.
For some reasons COMP- either is always >0V or <0 so U509 can not switch between the non inverting or the inverting path in the VGA amplifier.
It is a very simple circuit and I am almost sure I will fix it easily.
Stay tuned, I see the light at the end of this tunnel.
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[attachimg=1]
Do you see the bastard? 8)
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U514?
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I'll bet on CR501.
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If the signals are all DC, U514 is not working normal.
The current through R436 is rather high and there must be a way for it to go - looks like some path not intended: U514 is the main candidate, U515 is possible too. Q546 could be the culprit too though unlikely to be partially broken and the gate driver must be strong to still get 4.95 V.
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Yes all DC in Volts.
U514 is already been shipped to me. U515 was replaced before.
Funny thing it was the last AD847JR in stock at TME. After my order stock TME=0 Unit. :phew:
Another gossip is that U514 started up either generating an always positive -COMP signal or a always negative one (maybe the nature of a sick unit in a positive feedback). That's why I was getting either one set of errors or the other one.
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For a fist test one could try a more normal, slower OP for U514 (e.g. LM318, maybe LF356 or similar). Chances are one would install a socket for the suspect OP anyway.
A broken (conducting) Q542 could also cause the comparator to stay at it's state, as the hysteresis would than be quite large. However it can not explain the high current through R436 (unless R436 is broken). One could measure the other side of R279 and this way check if U515 is the culprit.
With the positive voltage at the inverting input the AD847 should normally be all the way negative, so there is something wrong with the OP (unless the circuit is oscillating).
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Well U514 was replaced,
Now I got:
404.1, 2
405.6, 8
there is another bastard on the board. :box:
EDIT: I forgot to point out that Q542 and Q546 are p-ch JFET
http://www.learningaboutelectronics.com/Articles/P-channel-JFET (http://www.learningaboutelectronics.com/Articles/P-channel-JFET)
http://pdf.datasheetcatalog.com/datasheet/calogic/J270.PDF (http://pdf.datasheetcatalog.com/datasheet/calogic/J270.PDF)
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[attachimg=1]
Unbelievable, check out U507 [everything in VDC]:
| TEST | Pin 2 | Pin 3 (-COMP) | Pin 7 | Pin 8 |
| 404.1 | 2,5m | -0,294 | +0,29 | +4,49 |
| 404.2 | 2,5m | -0,257 | +0,29 | +4,49 |
| 404.3 | 3,29m | +0,42 | +0,29 | +4,55 |
| 404.4 | 3,25m | +0,59 | +0,29 | +4,57 |
| 404.5 | 3,3m | +0,628 | +0,29 | +4,57 |
None of the circuits are oscillating. Because with the faulty U514 -COMP was always positive I could not detect that U507 was stuck and not switching.... FUUUUUUUU :horse: --> other 7€ to DHL for the next chip... :rant:
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hi, last weeks how i have some time, i begin repair two 2001.
first defect spend parts for second repair.
pcb blow up neer caps, repair pcb and caps, change relais and parts from power supply part, change all chips marked in blue!, change fan and pcb is running with many erros, but run :D. too many party needed so i do nothing more.
defect now :transformer frontinterface, completed frontinterface (display+chips), thermalfuse (ceramic), transformer ...
offer for new 2001 with many of discount is 2600euro, needed parts cost more!
(offer for rebuild front transformer 580euro, offer transformer 960euro, offer frontinterface 1800euro)
[attach=2]
second repair same, blow up caps, change many of chips same other repair (blue marked), use transformer and thermalfuse from 1. (transformer positions needs new screwhole to mount, hole now left bevor in middle of transformer , change fan ...
last error, Software 1991, A06, A01:
200.1 A/D
200.6 A/D
200.7 A/D
201.2 Testcal
412.1 ACA Switch
the 200.x are errors from firmware??
i reading her https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/500/ (https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/500/)
what can i do as next step??
for test i calibrated the 2001 and runs without errors. voltage and current looks like good.
[attach=1]
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The 200.x Tests are supposed to be mainly for the ADC itself. So this may be the ADC board. With a 2nd K2001 bad at hand one could try swapping the ADC board - however only after checking the supplies, to make sure not to damage the ADC board.
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2nd board has the same error 200.x.
i read that the firmware A08 has not the problem with 200.x. it is???? must change from A06 to A08?
https://xdevs.com/fix/kei2001/ (https://xdevs.com/fix/kei2001/)
https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/ (https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/)
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No the 200.x tests can be many things, causes. Often has nothing to do with the A/D board it self as with some of the needed signals , reference floating voltages.
I am still trying to find my cause, even have a good friend who has 20 yr repair experience on it but it is hard when the cause is not continuous.
His last thought about it is that due to the cap leakage some pcb trace inside the pcb has corroded might even make contact with other trace which influences the floating voltage reference.
Hard to find.
The meter it self is working and in calibration range on all inputs/settings, still get these weird ST errors.
https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg2303367/#msg2303367 (https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg2303367/#msg2303367)
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thanks, idea in wich part of board is to search?
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Iam concentrating on the traces near the powersupplies where the caps leaked.
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thanks, idea in wich part of board is to search?
A first part could be looking for the signals that are measured in the self test. The general idea of the test is to generate a test voltage and measure than. AFAIK one can run the self tests in a kind of single step more and thus have a more static mode of operation.
So one could than follow the path of the signal and do extra measurements with a scope or DMM, e.g. at the ADC inputs, DAC to generate the signal or amplifier input. This way one can often narrow down the area where the defect is.
Different firmware version could be slightly different in the acceptable limits for the tests.
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AFAIK one can run the self tests in a kind of single step more and thus have a more static mode of operation.
This, that's why I am investing time and energy in this old piece of equipment. The manuals (service + schematics) are awesome and the diagnostic test steps will make easy future fixes (I hope).
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thermalfuse (ceramic)
So R100 is a thermalfuse and not a power resistor? I am confused.
EDIT:
Original Part is:
RES, 470, 5%, 10W, VERTICAL MOUNT Keithely Part Number R-401-470.
Made by KRL/BANTRY code R-LF3476.
I replaced it with:
https://www.tme.eu/de/en/details/hs10-470rj/10w-resistors/arcol/ (https://www.tme.eu/de/en/details/hs10-470rj/10w-resistors/arcol/)
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U507 replaced, no more errors!
https://www.youtube.com/watch?v=vQhqikWnQCU (https://www.youtube.com/watch?v=vQhqikWnQCU)
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That was quite the adventure. Congrats, Zucca!
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Well done :clap: :clap:
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:-+ great result.
You tortured me a bit with the jodelahi video, but I'll survive.
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some pcb trace inside the pcb has corroded
How about let some current flow through the suspected traces and check with your Flir E4 if there are any hot spots? If a trace is corroded R goes up ---> heat will be generated there.
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must change from A06 to A08?
Try to upgrade the firmware and see what happens (Not wasting time, I would do it anyway). Are both your K2001 old A-Units?
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Guys slowly is time to think about low prio little parts.
I would like to buy:
1) 2 Nuts and 2 washers for the rear coax
2) If the rear writings are still good maybe I could upgrade the entire metal case
3) GPIB connector screws
4) Front Bezel with oder without display-key board
see the pics below regarding 1), 2) and 3):
[attachimg=1]
If anyone has something for cheap please PM me.
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thermalfuse (ceramic)
So R100 is a thermalfuse and not a power resistor? I am confused.
EDIT:
Original Part is:
RES, 470, 5%, 10W, VERTICAL MOUNT Keithely Part Number R-401-470.
Made by KRL/BANTRY code R-LF3476.
oh no, it is a resistor with thermalfuse. You find it in many device from HP and Agilent. Its an producer in USA, you can order it by them or keithley.
i open the ceramic resistor case and in this you find them in picture. i fixed it for testing device with new thermalfuse (red is original) and have order new in USA.
[attach=1]
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Thanks now everything is cristal clear, and finally I know why R100 goes open so often.
I do not like thermalfuse, I think I will take the risk to live without it.
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This constant regulation of effective resistance in series with the transformer regulates the power delivered to the instrument.
Interesting, now I understood how the Pre-regulator circuit works (service manual page 2-17).
Since the previous owner moron put his dirty handy on R100, I need to check if this circuit is working since is it not tested in the self test.
Moreover I have to be carefull around R100, it is main voltage territory.
:popcorn:
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I am in despair, my second batch of 27C4096 eproms i ordered is also not good.
They all fail on some bits , some can't be programmed at all.
Is there a modern flash chip, pin equivalent for this chip that anyone knows or a trustworthy source ?
I still would like to update the firmware to see if it solves my last error.