I've got a 3456A that I think has a problem, trying to measure a resistance above about 100k is a hopeless exercise.
The 3 least significant digits oscillate at about 1Hz. It gets worse the higher the resistance measured, with a 10M resistor it can't hold a value within 1% It also does this to a lesser degree on the voltage ranges.
I always figured it was just something I was doing wrong. But I figure if I get a 500k 1% metal film resistor, and clamp it directly into the screw down binding posts, I should reasonably expect that I would make that measurement, or is there something stupid I'm missing here?
I remember a thread maybe a year or two back (I can't find it now) which I think Vincent was talking about some caps in them always going bad over time. So I was thinking maybe there's some power supply ripple getting through and putting things out of whack?