On 16/01/2014 13:45, William Sommerwerck wrote:
I would simply flush out everything inside with contact cleaner. It's
more likely to be an accumulation of schmutz, than something wrong with
the electronics.

The uk has been permanently damp for about 2 months now. Perhaps
something has gone hydroscopic. Brushed meths over both sides of the
lower part of the pcb and allowed to dry off. Much the same 10s of megs.
When powered up and open I played a distant hot air gun over the dvm,
held in hand at the time so only hair drier temp and the o/c ohms
suddenly dropped to 10s of K . Let it cool down and gradually went to
33M and repeated switching on/off the last few times has stayed that way.
Reminded of a batch of Marshall amp pcbs that had contamination inside
them combined with damp perhaps and marked increase in conductivity with
relatively slight warming of the pcb, but HV there in that case