Keithley 2015-THD troubleshooting

[TheRuler8510]

Hello Group,

I am trying to troubleshoot a Keithley 2015-THD, and I am stumped.  The oscillator and THD functions work OK as well as the frequency counter functions, but it will not measure volts, ohms or amps, neither AC or DC. 

Any idea where to focus in on? Could it be a relay?

All the SMD parts are so small, they are difficult to probe, and there are no obvious bad or burned out components.

Regards,

Tom

[macboy]

Run the self tests, and address the lowest numbered tests first (failures in the lower numbered tests often cause failure in higher ones). Refer the the service manual linked by TiN, there are usually good troubleshooting tips in there including which components are most likely to cause certain tests to fail. No schematics unfortunately.

[casinada]

Make sure that the input selector switch is set to measure from the front if that is where you have the probes connected. 

[mimmus78]

I had similar problem on a Keithley 2000, everything was not working except the frequency counter. The problem was caused by U163 not switching the various signals for measurement.

If you have an oscilloscope put ground on the "hi impedance shield" and probe on the test point (TP105) near ADC and set meter to any V measurement. If you see a flat line this means is U163 not switching. Find why should be quite easy.

In any case start with Macboy suggestions.

[TheRuler8510]

Run the self tests, and address the lowest numbered tests first (failures in the lower numbered tests often cause failure in higher ones). Refer the the service manual linked by TiN, there are usually good troubleshooting tips in there including which components are most likely to cause certain tests to fail. No schematics unfortunately.

macboy--thanks for your input.  The power on self-test seem to pass as OK. The only other built-in testing is the display and keyboard test, and are OK.

I'll be moving on to the other troubleshooting stuff.

[TheRuler8510]

Make sure that the input selector switch is set to measure from the front if that is where you have the probes connected. 

Yes, that all checks out--no response from either front or rear terminals.

[TheRuler8510]

I had similar problem on a Keithley 2000, everything was not working except the frequency counter. The problem was caused by U163 not switching the various signals for measurement.

If you have an oscilloscope put ground on the "hi impedance shield" and probe on the test point (TP105) near ADC and set meter to any V measurement. If you see a flat line this means is U163 not switching. Find why should be quite easy.

In any case start with Macboy suggestions.

TP105 has seems to be working OK, as there is a different set of pulse trains for each mode, i.e. V, A, AC, DC, etc.

[TheRuler8510]

Try check analog modules per 2015 service manual.

TiN, thanks for the response, I'll check the analog stuff.

[mimmus78]

Power on tests exercise only ram and eeprom ... nothing else.

You should run Built-In tests as described on page 2-18 of the repair manual.

Take your time to study the repair manual ... raving around without reading it carefully will cause only unrepairable damages.

[TheRuler8510]

Power on tests exercise only ram and eeprom ... nothing else.

You should run Built-In tests as described on page 2-18 of the repair manual.

Take your time to study the repair manual ... raving around without reading it carefully will cause only unrepairable damages.

mimmus78, the self testing you are referring to is for the model 2000.  On the 2015 model, those self test do not exist, which makes it more difficult to troubleshoot. Unless I am missing something?

[ketil b]

the 2000 and the 2015 have the same MB.

"SHIFT" then "TEST / FILTER" will get you into the Built-In test menu

thanks

ketil

[TheRuler8510]

"SHIFT" then "TEST / FILTER" will get you into the Built-In test menu

ketil,

Right, same MB, but only two built-in tests, namely "Key" and "Disp." Believe me--that is all that is in there, as I have tried it many times. It is very strange that Keithly would drop those important tests from the 2015.

From the 2015 manual:

Front panel tests
There are two front panel tests: one to test the functionality of the front panel keys and one to
test the display. In the event of a test failure, refer to Display board checks for details on troubleshooting
the display board.

[casinada]

You're right about the display and keyboard tests only. Try to Check if there is a command you can send from the GPIB or serial port. I'll try to find out later myself.

[TheRuler8510]

You're right about the display and keyboard tests only. Try to Check if there is a command you can send from the GPIB or serial port. I'll try to find out later myself.

I don't see anything in the GPIB commands that does a self test, but then again the manual is a bit sparse on that subject.

Let me know if you find something, thanks.

[mimmus78]

 

Maybe they needed space on ROM for the THD stuff and deleted this autotest procedure from firmware or else I cannot find any good reason for doing it.

[casinada]

I just checked the service manual and there are no test commands beyond the 2 ones you've mentioned. It does test everything and only will show the display if the power on is successful.
There are commands for calibration but I don't think you want to get on to that part without proper calibration equipment. There are a few troubleshooting charts with voltages, logic levels, etc that might be helpful trying to find the fault in your meter. If you have spare flash memories you can probably flash the 2000 firmware and replace them to run the tests. I don't have a 2000. My firmware is B15 A02. I know that there is newer firmware (i don't have) but if you replace it you'll probably have to re-calibrate the whole instrument again.
Good luck with the troubleshooting.