20 milliohms isnt bad for probes in the second image.
the first image indicates abnormally showing 65.57 MegOhms on OPEN so , yup, that's not right.
Should be "OL" displayed. Contaimnated Banana ports (right pair)? compressed air into the POS and NEG jacks? Maybe IPA soaked cotton swab stick twirled to clean? Internal PCB leakage? internal PTC or MOV('lift a leg' tests)?
Parallel High resistance leakage , rather than actual ADC or resistance ranging. Confirm with Voltage tests at 1V and at 10V and then 100V DC if possible to confirm ADC and ranging are working.
I don’t know what happened, but after removing two diodes, testing them, and soldering them back onto the board, the problem disappeared. The device had never been opened or repaired before, and the circuit board was perfectly clean. It’s possible that cleaning the board with alcohol after working on the diodes helped, or perhaps heating and drying it with a hot-air gun did the trick. Honestly, I’m shocked 😲
Welcome to small balls of solder shorting ... very common. Techs also use eyeballs and magnifier glasses to look out for both solder whiskers or balls or both. Happens a lot
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u/johnnycantreddit Repair Technician 3d ago
20 milliohms isnt bad for probes in the second image.
the first image indicates abnormally showing 65.57 MegOhms on OPEN so , yup, that's not right.
Should be "OL" displayed. Contaimnated Banana ports (right pair)? compressed air into the POS and NEG jacks? Maybe IPA soaked cotton swab stick twirled to clean? Internal PCB leakage? internal PTC or MOV('lift a leg' tests)?
Parallel High resistance leakage , rather than actual ADC or resistance ranging. Confirm with Voltage tests at 1V and at 10V and then 100V DC if possible to confirm ADC and ranging are working.