Display on Mac 128K-to-Plus upgrade is blurry at corners, hurts my eyes

[djfitzgerald]

I am trying to restore a Macintosh Plus that started its' life out as a Mac 128K. As its' flyback transformer came busted, I spent the past month using the system with the analog board from a different Mac Plus. Last week, I gave the original analog board the flyback transformer from an early Mac Classic and put it in the Plus; this works, but the display is blurry and hurts my eyes. I believe it to be blurrier at the corners than the cente. It wasn't hurting my eyes with the other logic board, so I know the CRT is good. I replaced the C1 capacitor, resistor R9, and tweaked the focus POT, but the problem remains. I am in the process of recapping the rest of the analog board for good measure.

Does anybody have any ideas as to what may be going on and how to potentially resolve it?

Slightly related: I also have a Mac SE FDHD with a screen that does not appear to be blurry, but which also hurts my eyes. Thats been on my repair list for a while, but I haven't gotten to it yet. Any suggestions there would also be appreciated.

 

[bibilit]

The flyback from a Classic is not a suitable replacement for a Plus or 128 k analog board

 

[djfitzgerald]

The flyback from a Classic is not a suitable replacement for a Plus or 128 k analog board

I'd heard that, but I had also heard that was only the case for later Mac Classic analog boards, and the Classic II analog boards. Could you explain what the difference is between a Classic/Classic II flyback, and the flybacks used on the 128K/512K/Plus/SE/30?

 

[bibilit]

Don’t know really, but for me the rules are:

128/512/Plus
SE/SE 30
Classic I & II

Never heard any flyback from a group can fit another.

Classic and Classic II are very similar, only the connector from the board to the yoke is different. But those are an easy swap.

 

[LaPorta]

Don’t know really, but for me the rules are:

128/512/Plus
SE/SE 30
Classic I & II

Never heard any flyback from a group can fit another.

Classic and Classic II are very similar, only the connector from the board to the yoke is different. But those are an easy swap.

I agree.

OP, was it working before or not? If not, it sounds like it could have used a little adjustment in general, not uncommon.

 

[zigzagjoe]

AFAIK out of focus at the corners/edges is a symptom of a worn CRT, assuming that as you adjust the focus control you can get the picture sharp in the center but not at the edges. That wouldn't be an analog board issue, only "fix" is to replace the CRT.

However if you can't get it sharp in the center/anywhere, it's something else going on.

Hurting your eyes could be refresh rate: these screens refresh 60ish hertz which does not agree with some folks.