After a long wet day out in the field, my HP8560A has started giving
all readouts 16 dB high. With the input reference at -10 dBm, the
display says +6 dBm. Switching the attenuator makes no difference.
The very low level internal noise floor (atn=0) is also showing 16 dB
high but if I input known very low level signals there appears to have
been no increase in the true internal noise floor. C/N for very low
level carriers measure as normal. It is the display position and
readout values on the screen scale that are all too high. The RL
offset is zero dB.

Other old faults are non-functional up/down step buttons and
intermittent 0 buttons.
Any ideas welcome. Best regards, Eric