I recently brought my old Sony VPH-1270Q out of storage to use as a basement system. It turned on without issue, and ran for about 10 minutes before it just shut off on its own. I was playing with the convergence crosshatch when it shut off, and there was no indication of a problem. Now it only turns on for about half a second before it clicks off. I'm very experienced with electronic repair, but this one has me stumped for now, and I don't want to spend a ton of time on it. I do have the full service manual.
I've thoroughly checked it over for obvious problems like bad soldering, physical damage, water damage,... I traced the protection signals to the CPU board, and none of them seemed to be active in the brief time it would stay on. I also confirmed that the power supply voltages were present and not too high. I had to look at them with an oscilloscope because it shut off too quickly to take a reading with a volt meter. The HV is coming up just before shutdown.
Since it didn't seem to have an obvious fatal problem, I tried jumpering the power on signal to force it on. It will stay on and everything looks normal (rules out the power supply shutting itself down). All the protection signals at the CPU board are correct, the fans are running, there is HV and deflection, and nothing has blown up. I haven't left it on long enough for the CRTs to warm up yet because I would hate to ruin a good set of CRTs.
Does anyone have any suggestions before I pull the CRTs and wait for a 1271, or 1272 to show up on Craigslist?