I have a 7B92 (not the A version) plugin that has an odd problem. There's no trace in auto trigger mode unless it's triggered from a signal. Basically, auto behaves the same as normal.
I've confirmed that the voltage from the auto mode switch is getting to the sweep control IC (U310), and that the IC appears to be responding to the signal properly. I've swapped U310 (155-0049-01) with a known good one with no change. I've also confirmed that sweep is actually stopping when the trace disappears (it's not a blanking problem).
All other functions (including the delayed sweep) seem to be working. I think the trigger control logic is working, but I'm running into a dead end trying to trace things beyond that.
The service manual I'm using has a very poorly scanned schematic (downloaded from tekwiki), so tracing signals is not easy. It's split over multiple pages and just fuzzy enough so that you're not sure if it's an 8, 3, R, or B... I would appreciate any insight into how auto mode works compared to normal mode.
