Fluke multi. No AC or component test functions. Do I even try to fix? Can't win....

[fastline]

Just my luck, got rolled on a used Fluke today. Need a good multimeter. Instead I got another project or likely a lost cause.

This is a graphing model well over a decade old. Fluke does not support it anymore. I highly doubt I can get schematics from them either. All functions seem to work but when you switch to AC or the "component test (test mode for FETs)" modes, the screen just stays blank for the most part. When you push buttons, they all beep and act like things are working but no display. I don't suspect the display is bad though. Works fine in other modes.

there is also a self test on the meter which checks a few things but does not come back with any errors. However, apparently there is supposed to be a graph also displayed during self test which may be more of a display test and it only shows a small line segment and that is it.

Not sure what to make of it. To some extent, it seems there might be a display issue but i know from other modes that the display seems to otherwise work.

 

[Tony Stewart]

Check all solder joints and contamination. THen check voltage waveforms if you can on all interface pins. Failing that a VI scope trace with a small current source AC signal and series R to any junction can often find EsD damage on pins ( Huntron tracker method) with large capacitance and phase shift on 1kHz not being a linear straight line in XY mode on scope. but a round phase shifted trace due to ESD damage or shorts or opens.

or give up

 

[dr pepper]

The displayed trace might be off the screen, probably because someones stuffed mains up it in comp test mode.

 

[Mikebits]

Check all solder joints and contamination. THen check voltage waveforms if you can on all interface pins. Failing that a VI scope trace with a small current source AC signal and series R to any junction can often find EsD damage on pins ( Huntron tracker method) with large capacitance and phase shift on 1kHz not being a linear straight line in XY mode on scope. but a round phase shifted trace due to ESD damage or shorts or opens.

or give up

Is the like the old octopus tester?
**broken link removed**

 

[Tony Stewart]

Something like that... The capacitance of CMOS increases dramatically when wounded by ESD, (but not shorted yet), ( as do all diodes incl LEDs) so it detects faults not easily found when thousands of nodes and no documentation exists. No need for transformer, just signal and series R for current sensing and limiting with VI mode on scope. Sensitivity increases with f (kHz) for capacitance and also increases with forward voltage outside the rails of Vcc/Vdd, thus highly non-linear response beyond the rectangular zener-like curves can occur with damaged IO circuits.

Huntron has been a favoured tool for "supertechs" to debug unusual prblems. With two units (one known good) a comparison gives even more information.

\

Modern units have full schematics with fixtures for bed of nails and RF probes and memorized waveforms for automated testing.