I was helping my Mom prepare for moving, and the JVC 7860 we had with the Apple II plus turned up. The paperwork was still with it, including service guide and schematics. So I shipped it to my place and found it worked fine for a few days on my Apple IIe. Then failures started to appear. One failure is that text sometimes shows color artifacts (see image). The other is that scan lines get out of sync, with drop in brightness (see other image). These two things don't seem to happen at the same time, and cycling power may fix one or both. When switching on or off you can see a good picture appear very briefly. None of this happens with my other screen, a newish LCD that features a composite video input. I am posting (a) to share the technical sheet, and (b) ask if anyone has advice on whether/how the issues could be fixed.
Note: there is an artifact of the camera/screen timing leading to diagonal strips of light and dark in the photos.
Your images are not posted correctly. They are tiny and it's impossible to read anything. Always set the Display to Teaser, not Preview:
jvc-7860-color-failure.jpg
jvc-7860-scan-failure.jpg
jvc-7860-service.png
jvc-7860-schematic.png
It is highly likely that a cold solder joint is the cause.If you have experience, you should carefully inspect all the solder joints using a magnifying glass.You can also try touching them up with a soldering iron right away.Just remember to fully discharge the capacitors—you can disconnect the power supply for at least 24 hours before you start soldering.It is quite possible that doing this will resolve the problem.
Thanks Gregor for the suggestion, and thanks CVT for fixing the images. Use teaser, perhaps typing it will make me remember!
Please confirm that this is the correct unit that you are having issues with:
https://crtdatabase.com/crts/jvc/jvc-7860
If this is correct, given the age of the unit you are probably going to need to replace the electrolytic capacitors because they dry out over time. You might also consider replacing the IC's (see this video as a reference - https://www.youtube.com/watch?v=W45IO6vlqOw). This model has adjustment potentiometers externally and internally. You might want to clean those with some Deoxit.
I also agree with the possibility of a lose solder joint. Either way, safety first! Discharge the CRT twice before servicing. If you work on the unit over several days, do the discharge routine each day just to make sure that it hasn't re-charged somehow (some do). As previously recommended, discharge the capacitors as well.
Good luck!
Joe