yes i got the servicemanual, it includes a schematic.
when i was at it i changed the one electrolytic cap, but that didnt do anything any better. tought since its probably 20-25 years old.
when i was at it i changed the one electrolytic cap, but that didnt do anything any better. tought since its probably 20-25 years old.
I have this problem regularly, and normally I don't need that Meg range. This problem occurs because of the moisture in the pcb due to humid climate. Just heat the pcb under a 40-60watt bulb taking care not to heat the display.
I repair a lot of Fluke meters at work but there have been a few of the old 77's and 23's with this MOhm fault that I just couldnt repair.
I put it down to a fault with the processor but didn't have any replacements to try.
I put it down to a fault with the processor but didn't have any replacements to try.
Hi Flange_UK,
It must be leakage. It could develop in the PCB or divider, or some other component. There may even be moisture under the chip possibly. There is leakage somewhere, and the meter is only indicating what it "sees".
I wonder if sticking the meter in a warm, low humidity environment might work? It might be a week, but that is your best bet right now. If it wasn't such a good meter, you would probably never see this problem as it would be above the range of many others.
Have you cleaned out the function switch? You might want to try carefully removing it and clean it carefully. Hit it with some kind of moisture displacing fluid, then a zero residue cleaner. Lubricate the moving parts and contacts with some "barrier grease" Lithium might work. I've never tried that. Normally, I would have installed a new switch after cleaning the PCB underneath where the switch was.
I have a '77 I still use. It's great as an auxiliary meter on the bench. Heck, it's good enough as a main meter if that's all you've got.
-Chris
It must be leakage. It could develop in the PCB or divider, or some other component. There may even be moisture under the chip possibly. There is leakage somewhere, and the meter is only indicating what it "sees".
I wonder if sticking the meter in a warm, low humidity environment might work? It might be a week, but that is your best bet right now. If it wasn't such a good meter, you would probably never see this problem as it would be above the range of many others.
Have you cleaned out the function switch? You might want to try carefully removing it and clean it carefully. Hit it with some kind of moisture displacing fluid, then a zero residue cleaner. Lubricate the moving parts and contacts with some "barrier grease" Lithium might work. I've never tried that. Normally, I would have installed a new switch after cleaning the PCB underneath where the switch was.
I have a '77 I still use. It's great as an auxiliary meter on the bench. Heck, it's good enough as a main meter if that's all you've got.
-Chris
well thanks for the info.
i´ll take a closer look at the switch.
btw are the 77 and 23 the same?
i´ll take a closer look at the switch.
btw are the 77 and 23 the same?
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