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How to take apart Voltcraft/Metex 3650B

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retiredcaps:

--- Quote from: j-man on January 12, 2015, 12:53:08 pm ---It stopped working after I measured a resistor connected to a capacitor that was still charged... Big mistake  :palm:

--- End quote ---
BTW, what is the voltage rating of that capacitor?

My guess is that most of the older multimeters can handle at least 250V RMS on the ohm range setting.

j-man:
No, it was much less than 250 volts. I was working on an old Denon PMA510 hi-fi amp, which has a +/- 51v power supply. But I made a mess with the ground connections...
Both multimeters (one for measuring voltages and one for ohms) were connected to the same external power supply, instead of the internal battery. The "voltmeter" ground probe was also connected to the amp chassis. When I measured the resistor with the Metex it read over-range, but the buzzer also made a weird tone... It's just my guessing, but I suspect that something coming through the ground loop did harm to my DMM. A quite empiric diagnosis, I reckon  :-\

j-man:
Great news. Today I found in the mail the ICL7106 I bought: I replaced the old Maxim IC and my Metex is back in business, working like a charm :D :D :D

retiredcaps:
Thanks for reporting back on resolution and glad to hear your meter is working again.  :-DMM

Erik_Belgium:
Hi guys,

This is my first post since I can't find an answer online about my METEX M-3650B which is causing me a headache due to an always on "low battery" warning.
I've been looking and searching the web, read the ICL7106 datasheet and looked into the ICL8069.

I know it's an old meter but I've had it since college and I would like to repair it.
Took it all apart (which was an adventure on it's own ), checked the pcb and did test the battery with the it's own leads and it shows full ( added the 3,06V and 6,46V measured on the battery connections )

I don't have a scope to check, only another multimeter.

Where does the meter check it's low battery value? I can't locate the ICL8069 zener on my PCB.

It's the same version as shown in this topic from "Chicken".
The meter does seem to function normally except for the low battery indication.

thanks for any suggestions.
( I finally joined the EEvblog forum after watching Dave's channel and lurking on this forum for years. )

Erik.   

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