R. D. Davis wrote:
Picked up a cheap Fluke AC/DC differential voltmeter, model 887AB/AN,
at a hamfest this past weekend that's acting a little flakey. When
it's switched to battery operation, the meter deflects full scale and
remains that way until switched off. Any ideas? Is this a typical
failure with these? I haven't attempted to connect a power cord to it
yet since it has a few disconnected wires coming from the area where
the transformer, AC plug, etc. is and I haven't obtained a schematic,
calibration info., etc. for it yet.

The battery pack is said to be good, and I was told that it should be
charged once every week or two... not sure for how long though; will
the batteries be overcharged if charged for too long?


Pegging of the needle on a meter is often due to an open shunt
resistor. I am not familiar with this unit, but that is the first thing
I would look for.