New poster here. Found y'all in a google search.
I've been using an old Beckman industrial 9100 100mhz scope. It's been having trace problems. At first it would make popping noises and the trace would disappear. I would tap the top of the scope and it would come back. A few months back I decided to open it up and look for obvious issues. Found broken solder joint and 2watt resistor that had broken loose. I repaired them and it was back to normal.

Then it started developing the popping again, but trace would stay on. Then I turned it on one morning, no trace.......
Hasn't came back on and I've searched for broken solder joints and burnt components. My thoughts are a shorted cap.

I can't find a schematic and Beckman no longer offers support or documents.

Well today I read on this forum about injecting a signal on the z axis to troubleshoot and sure enough, I have a trace!

Without schematic, how should I troubleshoot now?
Start at the trigger controls and work back to its pr supply?

 

if you can get in on the z axis, that is usually directly coupled to the cathode. it sounds like the video circuits are bad. have you tried the BAMA site for a manual yet?

 

I'll check. Thanks

 

popping noises and the trace would disappear. I would tap the top of the scope and it would come back. A few months back I decided to open it up and look for obvious issues. Found broken solder joint and 2watt resistor that had broken loose. I repaired them and it was back to normal.

You need to have a really good look inside as you likely have other similar faults. Perhaps some dying (electrolytic) capacitors. Look for signs of arcing causing the popping noises.