EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: carl_lab on November 17, 2016, 01:10:09 pm
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A colleague brought me a defective 34410A.
(http://s7.images.keysight.com/is/image/Keysight/PROD-692834-01?$MAIN$)
Voltage and Ohm ranges show "house numbers" on display.
Current works OK.
Self test results:
- 330 Self Test Failed
- 612 Ohms 500nA Source Test Failed
- 614 Ohms 5uA Source Test Failed
- 615 Ohms 10uA Source Test Failed
- 621 Precharge Amp Zero Test Failed
- 621 Precharge Aperture Test Failed
What does current source have to do with voltage measuring?
Any ideas for locating the root cause?
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Check all voltage ranges. After that I will measure current in all ohms ranges.
Did you checked this thread
https://www.eevblog.com/forum/repair/hp-34401a-error-612-613-615-617-618-619-621/ (https://www.eevblog.com/forum/repair/hp-34401a-error-612-613-615-617-618-619-621/)
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Also, check this thread, I fixed a similar problem before.
https://www.eevblog.com/forum/repair/agilent-34401a-error-613-(ohms-5ua-source-failed)-help-please/ (https://www.eevblog.com/forum/repair/agilent-34401a-error-613-(ohms-5ua-source-failed)-help-please/)
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Voltage ranges:
<10V: display is counting up permanently
10V: works correctly PS: display is counting up permanently
100V: works correctly
1000V: works correctly
Ohm ranges (measuring current):
1GOhm: ~0.5uA
100MOhm: ~0.5uA
10MOhm: ~0.5uA
1MOhm: 5.01uA
100kOhm: 10.03uA
10kOhm: 100.64uA
1kOhm: 1.006mA
100Ohm: 1.006mA
Display (all ranges): OVLD GOHM
I know both threads you referred to.
Some time ago, when I had some 34401A to repair.
Most of them had similar error codes as this 34410A.
Root cause: mostly broken 24k chip resistors.
I didn't find the several 24k resistors in the 34410A input circuit, I found some 27k, they seem to be OK.
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With the 10 V range working, but the 1 V / 100 mV not, I would suspect the switching chips for the amplification or maybe the resistors involved. I don't know why but there DGxxx chips tend to fail sometimes. A failure in that area might also explain the errors messages, as it makes sense to use the 1 V / 100 mV range to check the Ohms current source or precharge amplifier.
Without an schematics it might take a little effort to find the chips. Locating the input amplifier and resistor network to set the gain should still make this possible.
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Without an schematics it might take a little effort to find the chips. Locating the input amplifier and resistor network to set the gain should still make this possible.
The Schematics are available for the 34410A but no longer on the Keysight website.
Send me a PM, if you need them.
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With the 10 V range working, but the 1 V / 100 mV not...
Sorry, I made a mistake when transferring from paper to forum:
10V: works correctly display is counting up permanently
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I am sorry for being late to the party - the house was burning here.
In my 34401A, the experience was that a missing Gowanda inductor in the input stage caused very, very similar behavior. I replaced the U201 opamp at risk at first, which turned out well (surprisingly, given my uncalm hand) but did not solve the problem.
The 3xxxx series measure their resistance via the voltage. So you need working DC voltage meas, before looking at fuck like current source. Oh, and sth evil: current path can be OK while voltage path is fucked.
P.S. If you need more on that urgently, pls PM me to remind me to come back here. The next week will also be hell.
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In my 34401A, the experience was that a missing Gowanda inductor in the input stage caused very, very similar behavior.
Gowanda sounds somehow african...
How could the inductor disappear? Voodoo? :D
BTW, my device is still under warranty, so I'll send it to our local service center to repair.
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Hello,
sadly no - Gowanda Inductor works of the VSA. I think they are in Neujork, but it could also be Neu-Jersey or Neu-Furzstadt for all i care - I am not good at Geography. What counts for me is http://www.gowanda.com/, (http://www.gowanda.com/,) and that no one can get me ONE of these fuckers.
As for how the inductor went MIA: dont ask me. The unit was shipped working and arrived dead. And as it was a 170$ affair two years ago, SWIMBO and I d g a f. When finally getting to it, we replaced the opamp on "fuckit", only to find out the problem did not get better. And then we started thinking and saw the two missing spots on the PCB and compared it to a working unit.
Was very embarrassing. We will make a video on it one day...
Tam
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Hello,
sadly no - Gowanda Inductor works of the VSA. I think they are in Neujork, but it could also be Neu-Jersey or Neu-Furzstadt for all i care - I am not good at Geography. What counts for me is http://www.gowanda.com/, (http://www.gowanda.com/,) and that no one can get me ONE of these fuckers.
As for how the inductor went MIA: dont ask me. The unit was shipped working and arrived dead. And as it was a 170$ affair two years ago, SWIMBO and I d g a f. When finally getting to it, we replaced the opamp on "fuckit", only to find out the problem did not get better. And then we started thinking and saw the two missing spots on the PCB and compared it to a working unit.
Was very embarrassing. We will make a video on it one day...
Tam
Why don't you un-solder the inductor from a working unit, measure it and and find out what you need and get a generic inductor from DigiKey or so?
Or is it so special, like the 1100V relay I could not find on my 34410A repair?
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I think they are in Neujork, but it could also be Neu-Jersey or Neu-Furzstadt for all i care - I am not good at Geography.
New York, New Jersey, OK, but "Neu-Furzstadt"? :-DD
Don't know any New Fart Town, did you mean Darmstadt or Pforzheim in Germany?
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Hello,
no, just a random bit of cussing to express my lack of interest in where Gowanda is based. They can even be based in Hell, for all I care...
Re Pforzheim: know about that town too well. But Austria has the funniest one, which goes by the name Fucking.
Tam
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If this missing inductor is in input filter, you could just use a jumper instead, to check function of DMM.
If it works, you could replace by another inductor, later.
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Hello,
Annette already found a similar one which has a little lower current rating. But as we rarely do high currents anyways, and as the DC Current path works, were prolly gonna risk it. But we already thought about a jumper ;)
Its now just a question of getting it done. I am back in my lab on the 4th, and then we will get to it.
But big big thanks for your concern, all!
Tam