| Attachment | Size |
|---|---|
 Screen Distortion on Apple Monitor II | 1.91 MB |
| Cross Hatch picture looks OK. | 2.09 MB |
| Grayscale pattern get distortion, too. | 1.96 MB |
Hi,
I have a picture problem on my Apple Monitor II (A2M2010) at near the top of screen. (Please see the attachment) I try to repair it by changed all Electrolyte capacitors, but they were not help. I need the suggestion what the components should have defective.
Looks like a V Sync issue. The picture of the Apple screen looks typical of early motherboards that had bad vertical sync generation. But the greyscale is obviously coming from a generator that presumably is outputting a correct signal. Other possibility is the input capacitor on the video input of the monitor. Are you sure you changed that?
That monitor looks like it is way out of adjustment as far as picture size goes. Both horizontal and vertical. In general Apple II video should have a black border around the displayable portion. The cross hatch pattern goes off the screen at the edges, and it shoudn't. Control may be better if the picture size is reduced to fit all in the displayable part of the CRT with a small border all the way around. Also brightness and contrast probably need to be adjusted. Brightness should be turned down so that lit pixels don't bloom out. Contrast should be set so the background is dark.
Wow! I made the assumption that the crosshatch and grayscale images were from a test pattern generator because they were overscanned. If all of these images are from the Apple, then I would agree that the first thing to do is adjust the H and V sizes. If that doesn't help then I would suspect the Apple and not the monitor. What Rev motherboard is it?
My Apple II mainboard is very old. It should be Rev. 0. The picture from pattern generator are overscanned because I use the pattern generator for PAL system (625 lines) to test with the monitor.
Do you have this issue if you plug your monitor straight to the back of the Apple II and not though the 80-column card?
Btw, is your motherboard really a Rev.0 - you sounded like you are not sure. A small detail worth several grand last time I checked on eBay. :)
Yes, I have the same problem in 40-Columns mode, too.
Finally I found the root cause of the problem which came from the sync signal problem from my Apple II Rec.0. I found many document to discuss about the same problem on other monitors. Then, I switch to Apple IIe, there is no problem anymore. Thank you for all comments.