I started this new thread because my previous post about it was in an old thread about a similar one. It seemed better to start a new thread. (Hopefully not a noob mistake...???) I wanted to copy the advice I'd gotten so far as to avoid duplicate info.
From Barry Bennett
Quote:
Troubleshooting a scope without a schematic is going to be extremely challenging. That said, blowing a fuse 5 seconds after startup sounds like a perfect candidate for old power supply filter electrolytics that need to be replaced. Of course, it could be about anything, but that's where I'd start while searching for a schematic.
If it blew the fuse instantly, I'd be more inclined to suspect a shorted rectifier or power transistor. The 5 second delay seems to indicate an overload rather than a dead short somewhere, but of course, no guarantee. Easy to check the rectifier or bridge, and any higher power transistors.
Second suspect for me would be something in the HV power supply, but you can pretty easily eliminate that as the issue by just disconnecting the power going to the HV section of the instrument. For this, you WILL need the schematic. H or V deflection would be the third suspect, and again you'd need the schematic.
From Tim Tress
Quote:
I suspect the capacitors in the HV power supply.
Another common scope problem is drifted resistors around the intensity and focus potentiometers. Check the voltages in that circuit at turn-on, and see if they go down.
