Recent content by monzamess

For closure: it was the flyback. I picked up another grungy Mac Plus with a working display. I did some parts swapping and tried every combo of analog board, CRT, and logic board. The problem followed the old analog board. Then I swapped flybacks between the analog boards and the problem...

Thanks everyone! I think my next step is to buy a parts unit with a newer (and working) flyback. I wouldn't mind replacing my CRT as well since it has burn-in.

I haven't done anything with the logic board. I attached an image of what I think is the video logic...? Appreciate the help.

Here are a few things I just tried. The problem persists -- no better, no worse. 1) Replaced C1 again. My original replacement was a NOS electrolytic and I thought maybe it was bad too, so I put in a ECW-FD2W395K 3.9uf film capacitor. No change. 2) Replaced the horizontal output BU406 at Q3...

Thank you for responding. The main rails are 5.04V and 12.1V and steady. If you are asking about voltages in the CRT drive circuitry, I am not sure what to measure.

The problem starts as soon as I turn on the Mac. I did try it without the floppy attached and no change. I'll look into replacing that transistor. I attached a video of the problem here to better represent it. (note: the image doesn't sway back-and-forth -- that's me being unsteady holding...

Update: Swapped out C1; no change.

Clarification: My cap kit didn't include C1 so I didn't replace it. Mine is electrolytic. I've seen it described as the "horizontal deflection capacitor" and highly likely to fail, so that is very suspicious and I will find a replacement for it. Other ideas still very welcome!

Hi, first post, glad to be here. I have a new-to-me Mac Plus. It appears to be an earlier Mac that was upgraded. It has the Samsung CRT and the "early" flyback transformer without yellow(brown) glue on it. It has a 4MB RAM upgrade. The problem with the CRT is that some horizontal rows will...