AFG3021 self calibration error

[analogRF]

I recently bought a used AFG3021 (fairly cheap I guess at $325 delivered). It seems to work fine and I cannot find anything wrong with its output waveform but when I do the self CAL it gives error 1103,0 (CH1 Output offset calibration failure) all other tests pass OK.

Anyone has experience with these units? Where should I start troubleshooting for this error? I thought it must be a DAC or Vref (related to the DAC) which is in the self calibration path. I see a PCM56PU on the board and that seems to be the only DAC. Is that it? But if it is faulty I should be getting more errors because it must be responsible for more parameters than just offset, no?

How serious is this error? because when operating the unit I cannot really detect anything wrong with it.

The firmware version is 1.04 Sept 2005. Can I upgrade the firmware from the file that exists on the TeK website?

your help is greatly appreciated
thanks

[analogRF]

this topic is closed for now as I have accidentally killed the signal generator. please see the following post

https://www.eevblog.com/forum/testgear/tektronix-afg3021-died-firmware-update-gone-horribly-wrong-(/

i have also posted on tektronix support forum

any help is appreciated