Macintosh Plus Display vertically compressed

keelus

keelus

New Tinkerer
Jan 5, 2023
24
7
3
Hello! I've been working on my Mac Plus for a month and I got this issue out of nowhere.
IMG_6303.jpeg

(The diagonal lines are from the camera)​
As you can see, the display is very compressed vertically, strange display resolution. I tried adjusting the height potentiometer, but it's maxed out, if i turn it in the other way, it goes even more compressed.
This is what I have done to this Mac Plus so far:
  • For other issues I had (no display, clicking, and sad mac):
    • I replaced these electrolytic capacitors for brand new ones: C2,C3,C6,C7,C10,C12,C18,C24,C27,C28,C30,C31,C32,C34,C35,C38,C39,C42,C45.
    • I replaced the U3 optocoupler for a 4N35.
    • Brand new RAM (x4 256k)
  • Trying to fix this issue:
    • LM324N - Brand new
    • Q3 (2N4401) - Brand new
    • Q6 (2N4401) - Brand new
    • Q4 (MPSU51) - Brand new
    • CR15 - Brand new
I need help to fix this. Does anyone went throught this problem/know what could be causing it?
Also (might be a dumb question), if I buy a different potentiometer to control the height, could I make it stretch a lot so it matches the correct vertical height?
Any kind of help or suggestions will be appreciated.


Thanks for your time,

keelus
 
How could I test if the flyback is bad? The resistors and diodes controlling the vertical deflection work as they should.
 
Sadly I don’t have one that’s known good. And from what I have seen, new ones are very expensive. Will try resoldering the flyback joints and see if that helps…
 
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