Mac SE/30 Display Issues: Analog Board?

  • Board Nominations
    Nominations have now closed and the results are available here.
  • Hey Guest, MARCHintosh 2026 is upon us. Check out community projects, join GlobalTalk, and have fun!

powellb

New Tinkerer
Mar 6, 2025
2
0
1
Greetings,

I had my SE/30 running all of last weekend for a #Marchintosh project I was trying. While it was on, I turned the brightness knob to blacken the internal CRT. On Monday, I turned it back up, but I had to go to full Maximum before I could start to see any image, and the image that was there was completely stretched off of the physical bounds of the CRT (see attached photo). The horizontal is extremely stretched and the vertical is compressed but cuts off half of the display. My primary display is an external VGA with an SE/30 video card from zigzagjoe.

I opened the case and adjusted the brightness (the camera is making it seem brighter in the photo), stretching, etc. potentiometers to no avail. I physically checked the flyback transformer and the analog board with no apparent issues. I had reflowed and recapped the analog board 18 months ago. I recapped the logic board 2 years ago. I have a modern babyface power supply.

I thought maybe there is an issue with the CRT, particularly because the brightness hardly works any longer. I had a spare CRT from a junked Classic. I swapped in the other CRT, but it behaves in the exact same way. This means the only suspect (to me) is something on the analog board is no longer driving the CRT properly: very low brightness, mistimed driving of the horizontal and vertical scanlines, etc.

Any ideas what this could be and how to fix? Thanks!
 

Attachments

  • mac.jpeg
    mac.jpeg
    637.4 KB · Views: 30

powellb

New Tinkerer
Mar 6, 2025
2
0
1
I have been working trying to figure this out, and it seems that the issue is with the "width" control circuit. When I put a metal hex driver in there to turn it, the screen width gets much smaller, and I can adjust it. However, once I remove the small hex driver, it immediately reverts to the image uploaded. Additionally, the hex driver gets very hot.

I recall reading years ago of people using small metal objects in there to correct it (homemade coils or screws), but I would like to know what the issue/correction is. I imagine that component is now unobtanium (other than to recover one from another board).

Any ideas on the width control circuit? The capacitors connected were all replaced as per above during the recapping.