Resistor Test problems Fluke 75 Series II

[kdl1950]

Hello everyone, I have a problem again.

This time with a Fluke 75.

The error lies in the fact that a value of 0.00 ohms is not possible when measuring the resistance.
If the input is short-circuited, the measuring device starts at approx. 20 ohms and runs to a final value of 1.2 ohms in approx. 1 minute. (see pictures).
I have already tested internally without the connection socket. Same error pattern.
Thus the bushings can be excluded. The cable is new and tested on other measuring devices. It looks like a capacitor is changing?!?!

Does anyone have an idea or knows the problem? I checked the various internal resistances. All OK.

What is also noticeable is a similar problem with the diode/continuity test.
It takes a certain amount of time until the value approaches 0.00.
It won't be quite 0 either.
Continuity testing works immediately and has no problems.

Greets from Germany

[m k]

Manual has Schematics.

Get hair dryer and non conducting cold spray can.

Warm up the thing with a hair dryer.
If lower resistance value appears sooner than without the dryer move to the next step.

Learn to shoot cold spray so little that only a single drop comes out.
Put that drop on the suspicious component.
You can also drop it on a single pin.

With luck you find a source that is external.
It can also be a dirty selection wheel.

[steerage250]

Any luck solving this?  (I have the same problem - and I don't want to through-away my faithful old Fluke!)

I found a service manual for it on the Fluke website, but the schematic and component layout differ from my circuit board (the differences start immediately at the V/ohms input terminal where the schematic shows it connecting to 2 resistors, whereas mine connects to one resistor and the spark gap device)

[kdl1950]

Hello steerage250,
yes, there are insights and I can make it relatively short.

I found the crucial clue here: "Fluke 77 III Resistance measurement fault"

U1 has a defect or breaks.

I heated the chip properly for a short time using a hot air dryer.

The result is or was that the resistance measurement immediately goes back to 0.00 ohms. Unfortunately the measurement drifts away again after a few days.

You can try it.
The problem is definitely with the chip U1.

I just reheated the chip. Here the result. From 0.02 to 0.00 in about 5 seconds.

It remains to be seen how long the “repair” will last.

At some point even a solid multimeter will reach the end of its life.

[squadchannel]

Is it any chance that the solder has cracks in it?
If it does not work after re-soldering, then give up