Wierd DMM issue - can't seem to get a reading

[MikeH]

Anyone had anything like this happen to them?  I'm modding a mic pre that I have (Nothing fancy just swapping the opamps) and I figure while I'm in there I'll put in an LED to illuminate the VU meter (It's a Bellari RP503 to be specific).  I'm using my DMM to find a place to get power for the LED but every time I try to get a voltage reading it starts high and immediately jumps down to about 1 or 2 volts, and then keeps trickling down from there.  What gives?  I can't get any voltages off this damn thing!

[aleister]

try to measure a 9 volt battery with the dmm, if it still gives a screwy reading check the battery in the multimeter. this happened to me a couple days ago and i did not think it was the battery cause the low batt indicator did not come on but once i put a fresh 9v in i was back in bussiness. good luck, i hope it is that simple.

[amptramp]

A lot of the time, the probes will not pierce the crud that is on wires.  Oxidation and flux quite often keeps readings from being correct.  The other cause is the selector switch gets oxidized and needs a shot of contact cleaner.  One trick I saw technicians use on a military program I was on:  instead of probes, they would use wires with banana plugs on each end.  One end plugs into the DMM and the other into a #28 tuberculin needle,  This is sharp enough to probe right through most insulation and will pierce most oxidation.

[MikeH]

Batteries read fine- and I did put a fresh battery in my DMM.  I'll try and make sure my probe is piercing and goop that is insulating the traces.

[MikeH]

Well that's not it- is it possible it has some sort of protection circuitry built in?  Even when I probe with an LED/resistor at a spot where I', sure there's good voltage (like on the regulators or the collector of a transistor) the LED lights for a second and then goes out (the LED is not blowing btw, I checked it after).  A little while later I can probe the same spot and get the same result. Weird!