Since my Apple II+ is modded for the PAL region and I don't have a PAL encoder card, it can't display color. So I decided to restore it to NTSC, but the result is not so successful.
As you can see in the video, the display is far too bright and unstable, with visible vertical bars. It is mainly in text mode that the image flickers, in color mode it is slightly more stable (but still too bright with visible bars).
To restore it to NTSC, I have made the following changes:
- replaced the crystal with a 14.318 (from ReActive Micro)
- removed the solder blobs from the circle jumpers on the motherboard
- joined the triangle jumpers on the motherboard
- removed the wires from B10 and B11 to slot 7 on the backside of the motherboard
I've adjusted the composite trim pot and it is set as good I can get it. I've also adjusted the color pot and I think the colors look as they should.
Does anyone have any suggestions on what the issue might be?
I should add that I've tried to do the same modification once before, but with a crystal bought at the local electronics store. The result was pretty much the same (with some additional issues). What I then noticed was that it was when I changed between bridged circle jumpers to bridged triangle jumpers that the problem with the washed out and unstable image started. The replacement of the crystal itself had no negative effect on the image quality.