Hi All,
Have been watching Dave for the last few years and thoroughly enjoy his videos. Recently, I picked up an old Fluke 88 for cheap and found it accurate with one exception: the lower DC voltages do not indicate correctly. Specifically the 4 and 40-volt DC range. Hopefully, someone here can point me in the right direction.
Details: This is an automotive meter. The AC Volts, amps AC/DC, ohms, diode check, and DC millivolts all work fine. The DC ranges 400 and 4000 also indicate just fine compared to a power supply. When DC voltage is selected in the 4-volt range with no voltage applied, the meter indicates -OL and -16.16 in the 40-volt range. The negative voltages do not change if the V and COM are connected. If you zero the meter and apply voltage, the meter indicates about 60% at 10VDC. At higher voltages, the gap between applied and indicated increases; at 32 VDC applied, the meter indicates approximately 55% of the applied value.
What I have checked:
Wafer switch - resistance checked and found to be good. Cleaned
Both fuses - good
1K fusible resistor - good
Resistor Net - checked resistance from the processor chip to the wafer switch. All resistances were found to be within specifications.
The board looks nice and clean with no burn marks, cracked solders, or apparent damage.
Any help is appreciated.
Thanks