Monitor Apple 12" RGB M1296Z V sync issues and ...

[ironborn65]

I have a Macintosh 12" RGB M1296Z that was working properly until the image on the screen became slanted and compressed along the vertical axis.

I disassembled the monitor and found three leaking capacitors in what I believe are in the VSync section.

I was unable to find a replacement for the 83 µF 160 V capacitor, and I was advised that a 100 µF could work as a substitute. It was noted that in case I could have adjusted the rear potentiometers, to compensate any vertical compression or expansion adjustments I might have had.
Mmm .. I was skeptical, but I don’t have deep knowledge in this area.

The capacitors marked with 'N' have been replaced. The empty position circled in red was for the 83 µF 120 V capacitor, which I replaced with a 100 µF 120 V capacitor.
Now, the screen shows a white image with diagonal stripes, which seems worse than before, but at least the "image" is whole screen. Adjusting the contrast and brightness knobs has no effect.
Can you advise whether using a proper 83 µF capacitor would likely solve the problem, or if something else might have failed?

 

[Durosity]

I can’t comment on whether the 17µF difference would cause this issue or not (I suspect not but I don’t have enough knowledge to say for sure), but did you test the new caps before installing them? I’ve found that some caps tested ratings vary wildly from what they’re actually supposed to be. When I recapped my 14” Macintosh Colour Display it started to work again, but with weird distortion.. I then removed and tested the caps and found some were out by 40%… replaced them with other ones that closer matched the spec and boom, the issue was gone!

 

[ironborn65]

mmm, not really, they were all brand new and from known factories ... this does not prove much, but, no, I did not test them.
The ESP can be critical, but I thought I could improve the parts later if the image was not good enough, but this is ...bad!

 

[ironborn65]

Shame on me — the brightness connector had come loose during disassembly.

Now the image is back, but I still can’t set the brightness and contrast correctly: it’s either too dark, or, when I increase the brightness, diagonal stripes appear. From this, I can reasonably conclude that there is a reason for using a precise 83 µF value. I’ll order the correct, high-quality capacitors and replace them.

Thanks for taking the time to read this.