Electronics > Repair

Fluke 77 iv - erratic behaviour

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cardosoluis:
Hello everyone,

i bought a fluke 77 iv for parts/repair, and i thought it would be a fun and simple project to repair since in the pictures it look like it was working ok, only strange part was that in the volts selection, would show ohms, a few days later and i have it with me, and the multimeter has a really weird behavior.

when i turn it on, despite what measure i chose, i always get the same screen in ohms and it beeps randomly, like i was measuring continuity, after taking it apart i saw that the previous owner soldered a wire in the fuses (probably that's why it got in this state).

Visualy i don't see anything wrong apart from that, if someone has any ideia of what the problem could be, i would apreciate your help!

i'll attach some pictures of the meter

cardosoluis:
Forgot to mention, the bridge rectifier looks like was resoldered, also the battery connector doesn't look oem.
also added pictures of the meter running and a video:

https://youtube.com/shorts/DXS7XyqXIfE?si=lsCTkQ1AN_zlttl2

lowimpedance:
Are the switch contacts still all there and in correct positions, (in the function switch in top case half!), given this unit has been worked on before you ?

You may find the below thread useful.

https://www.eevblog.com/forum/repair/fluke-77-repair-184173/

good luck

cardosoluis:
yes they are, i saw a video where one of the contacts was broken so was my first check, i already saw that thread and tested all that, and its fine on mine.

i ordered a new bridge rectifier to test, lets see.

Thanks!

cardosoluis:
i'm guessing the issue is not with the bridge rectifier, i removed mine from the board, and the strange behaviour persists, if anyone has any idea please let me know

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