Tektronix DPO7104: all channels have high offset

[thefloe]

Hi,

Some time ago my DPO7104 failed to start and by exchanging the hard disk and disconnecting the cdrom drive I managed to get it up running again. Unfortunately there is one remaining problem: all four channels show an offset in the range of 200mV to 500mV and the offset is depending on the vertical range setting. The amplitude shown of the signal is correct. Also timebase is correct.
I had the scope running over night, the offset do not seem to drift or change with time / temperature.

SPC fails without showing much information and system diagnostics shows only a 412 code on the trigger system. Which relates to CH2.

Any idea on how to get rid of the offset without sending this outdated model to repair / service?

Thanks a lot,
T