Recent content by mdhokie

OK. So after all that troubleshooting I just reconnected the vertical deflection yoke and tried again. And it works now. So what did I learn? Nothing. I still have no idea what caused the fuses to blow initially. None of the solder joints I reworked looked bad, I saw no shorts anywhere...

I did another experiment, because I was unsure whether the no-load of having the vertical deflector yoke disconnected was affecting voltages etc. in the circuit. So I hooked up a 1k resistor in between the disconnected wire and E27, to give it at least a little load without allowing enough...

OK I did a lot more troubleshooting and have to admit I'm stumped. Anybody understand this design enough to know what's going on? I have lots of information though: - I have the wire from post E27 disconnected (one side of the deflector yoke vertical coil) to keep it from blowing the fuse...

With horizontal output wire reconnected, tube does indeed light up, and I see the lower voltages are present and roughly the correct values. Hey that's progress! Now to figure out what's going wrong with the vertical output...

Got more fuses. @Hugo Holden : Today I tried disconnecting the white wire from above the resistor that says "vert out" that goes to the tube. Not sure if this was what you meant by disabling the vertical output, but it was an effective test. With both that and the horizontal output wire...

Disconnected horizontal output (Q101) black wire that went to the high voltage, still blows fuse. So still hunting, but that definitely seems like a useful test. That was my last spare fuse though, so I need to go buy some fuses before I can do any more disconnect/fuse experiments with the...

Thank you! That sounds like a good place to start. I can definitely do that, and see what happens. I understand basic circuit components, but don't have any experience with CRTs so I don't understand the block-level circuit designs. Regarding the hot chassis; it's wired to neutral, and I know...

Update on diode readings: - CR7 is indeed parallel to a resistor in the circuit which would explain the resistance in each direction, and isn't shorted or it would be 0 ohms - I removed CR19 from the circuit and got a good diode check voltage, so I put it back. Every resistance reading I make...

I bought a TRS-80 Model I (Level II) and monitor at the VCF East event this weekend. Awaiting purchased power supply to test/troubleshoot the computer, but the monitor definitely doesn't work. The 1A fuse in the power supply was blown; replaced it and blew again immediately so troubleshooting...