I just got an HP 1661C logic analyzer for cheap, the first 20 minutes or so, it worked like a charm. However, it suddenly started making some crackling noises, and it smelled like burned electronics. I immediately turned it off and when I turned it back on again, it made clicking noises and the CRT only showed a single line. With a quick Google search, I was able to find the service guide, which had a guide for troubleshooting the PS. From what I could find on the Internet, it is apparently a weak point of this machine. The first time measuring voltage rails under load showed the same problem, my multimeter jumped between the 5V it should have and 0V. After powercycling, it started working perfectly fine, every voltage rail was perfect. After connecting everything back up, the logic analyzer booted up just fine.
I am not quite sure what the problem was or is. My first guess would be some bad caps however, none of them look bad. Does it make sense to do a complete recap of the PSU and the CRT control board when I am at it? I was not able to find a replacement PSU on eBay, so I have to work with what I have.
Thanks in advance!