So, i'm in the middle of restoring a recent eBay purchase, a very low serial number Bell & Howell Apple II. The unit is remarkably unscathed after 43 years, with a case in near perfect condition. The hardware inside is all Apple-manufactured. There's just one problem. The video is out of sync..and I dont know enough about how video works to fix it, or even explain what's going on.
What I _do_ know is that there are two adjustable potentiometers inside the case near slot 7. One adjusts the black level, and one is labelled "color trim". Both the black level and the color trim can be adjusted nicely, but, the frame of the image itself is slanted diagonally, and seems to drift both horizontally, and vertically, slowly.. Here's a video or two explaining what i'm talking about:
Video problem vid #1 (I power off/on the unit a few times over the course of this video)
Video problem vid #2 (I power on the unit, and power it off)
For what its worth, the definition of the text itself seems fine. Each letter is well-defined, clear, and crisp...its just the sync timing of the image itself that's all jacked up. Where do I begin to diagnose this? I have a spare Apple II+ that I can pull parts from...can this be solved with a simple chip replacement?
The only other thing I can think to mention is this -- I recently had a peek inside, and discovered there's some sort of daughterboard plugged into an area (or near an area) i've read is associated with producing the video signal. Does anyone happen to recognize what this might be?
Any light anyone might be able to shed would be greatly appreciated..I'm new to Apple II hardware diagnostics, and doing my best to do my homework, here, but i'm at my limit of understanding. :(