Electronics > Repair
[SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
JohnAH:
yes, i just checked, i mixed them up
R I Range
100ohm .998mA 100 range
1k ohm .998mA 1K range
1k .o991 mA 10k range
1k .0094 mA 100k range
80k .0043mA 1M range
80k .00012mA 10M range
u201 was new. QS
Dr. Frank:
All right, now the 500nA seems NOK, but already the 5µA might be just an error from your other DMM, due to lack of resolution. What other DMMs do you have?
Please try to measure with an appropriate 1% shunt, to decide, whether the sources are ok, or not.
What about Q201, 202? Have you changed anything with them?
Or what's the meaning of to "swap out"?
In which range and mode did you measure the voltages in your diagram?
Open jacks, or something connected?
JohnAH:
Sorry it looks like half the message I sent last was truncated.
We don't have any better DMMs.
both Qs were known good used stock. They were not swapped with each other.
The diagram was 2 wire auto range, open jacks.
I can probably get high ohm precision resistors but it going to take a little time.
The meter has been working for a long time. It died when a customer borrowed it. It is being used to verify accuracy in a ICT machine via IEEE program.
Dr. Frank:
OK, under these circumstances, at first please measure the voltages with a load connected, e.g. 1k resistor in 1k range.
I assume, that U201, Q201, Q202 are fine, as the currents might work ok, as far as one can tell from your measurements.
If you have a 2nd 34401A, then you might measure the 80k resistor precisely, use it as a shunt, and measure 10µA and 500nA, using the 2nd DMM in its 1V and 100mV range, i.e. about 800mV @ 10µA and 40mV @ 500nA, but with much higher resolution. Simply use a calculator, and set the 34401A to R > 1010 Ohm. The absolute accuracy is not important, 1% is fine, but I just want to get rid of offsets and alike.
I assume that the transistor array might be damaged, or the 3rd FET which goes to GND.
Didn't we have that here, recently?
Sorry, need to sleep a bit now, continuation by tomorrow.
Frank
Dr. Frank:
Another idea: Please check if a 10V dc signal is read correctly in the 100V range, compared to the 10V range. maybe the relay is damaged, as it's used also for all these failing tests.
I assume, that the Ohm circuit was not damaged at all, initially (have you checked the correct function before you changed the components?).
Only the 5 tests for current source compliance failed, but that could also be caused by components in a completely different section, like this relay, or other components inside the DCV path.
Therefore please check all DCV ranges also.
Frank
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