I saw your question go by on groups.io too.
I don't think the 9361 schematics are around anywhere. (other than the PSU that AFAIK is common to the 930x, 931x)
Just my typical "luck".
I've never owned a 9361 but they are like the 9362 or Tek TDS600 scopes with a fast CCD sampling then slowly clocked out to a modest ADC.
The 9361 may share some common components with the 9310, hopefully the analog frontend and trigger IC's. (The service manual is available.)
Are you sure it's the 9310 you meant?
I can't seem to find the service manual for that model.
Maybe you meant 9320 instead (in which case the ext trigger input differs from the 9361)?
Could you post some detailed photos of the PCB that could give some clue to how things ate tied together.
Sure. Please see below (for the close up on the external trigger input, please don't mind the missing op-amp and transistor - the green rectangle areas - I removed those as part of the troubleshooting, but that made no difference to the error on the screen).
A not so uncommon problem is failure of an analog MUX between the DAC that generates the various control voltages and the components these control voltages are meant to reach. (Output stuck high to trigger level control or offset compensation voltage.)
On other 9300 models the scope will self calibrate on powering up, if the calibration signal that's switched-in to the F.E's (can't remember if that's square or DC) is stuck too high it could lead to some error, not sure if that would come out as an overload or Cal error though.
Hmmm... Thing is, at this point in time, I am not convinced there is anything wrong in the external trigger input and a communication path issue is something that did cross my mind.
However, I have no hard data to support this.
FE and Trig circuitry should be identical between channel inputs and ext. trig. Assuming the problem only hits the ext. trig you should be able to do some comparative probing.
Amm... I'm not sure of that, but happy to be proved wrong, based on the pictures attached.
Are you able to access the maintenance menu and read the error logs?
No, but maybe because I didn't know how to get there.
Is it based on a combination of soft keys being pressed at power up?
Or is it by navigating through the various menu options?
If the former, I don't know the key combination for that (so far, I've tried only soft reset and hard reset key combinations).
If the latter, as I mentioned before, the scope gets stuck in the boot process and there is no menu/option to select.
Thanks!