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After some extensive testing, I found that it's definitely a broken solder joint somewhere on the analog board. When I lightly press the upper corner of the board inward (at the location of C1), causing it to flex just a bit, the screen comes to life. I reflowed the major connectors (J1, J2 and...

I reflowed J1 but that didn't fix it. Also, ChatGPT says that the cathode is expected to be positive since the bias is negative, and that +50V DC is normal. If that's the case, then all voltages on both the analog board and logic board are correct. But still the screen is black

Hi All, I recently acquired a non-functioning Mac Plus 1Mb in good physical condition. It boots and gets the chime on startup, all of the usual signals and voltages are present, but it has no image on the screen. I think I have traced the issue to a weird voltage reading on the CRT cathode...

Are you testing the PSU under a load, or just connected to the scope?

Thanks for all of the fantastic information in this thread. I am preparing to recap a faulty TDK 699-0153, but in addition to new caps, it also seems L52 has failed. Does anyone know the exact specs on that inductor? I am finding a wide range of 4.7uH inductors on Mouser, with various current...