I've been building a good Mystic Colour Classic out of two flaky ones ...
- One in perfect physical nick but seemingly had the Mystic mod attempted, and failed. Chimes and boots but no video
- Another CC sprayed black with successful Mystic mod *but* sound chip removed! Has yellow tint on screen.
So, I desoldered the sound chip off the better one and got the "good" Mystic AB working, in the good condition case, sound and VGA video working.
Now it's all going a treat but it the yellow tint still remains. Adjusting the green or red pots on the AB (for drive and background respectively) elicits a change in hue but adjusting blue drive does nothing - no perceptible change.
I've resoldered the PCB at the back of the yoke to no avail - which leaves me with the AB - could there be a cold solder joint somewhere, where should I look/start?
I resoldered the R/G/B cables going to the analog board to nil effect. "Banging" around the CC will make the CRT jump.
I trust you already played the swap-game: putting M/B and HD into the CC with chime but no video. I'm not sure if the missing video is to be blamed to a bad A/B.
Beyond that, I'm afraid you have to re-check all wires, especially in the harness. Missing tint is annoying.
I have the same prob temporarily and so far I haven't yet invested the time to go thru the harness.
If all that doesn't help, the good news is that CCs have come down in pricing and it should be possible to get a working stock one and pull the A/B. (It's sometimes cheaper than to invest hours over hours of spare time to get something working.)
Good luck anyway! Make sure to post the solution in case you can make it.
Thanks for your reply Hansego - appreciated
I thought she was a goner but I did get it working. Ended up taking out the AB and retouched/soldered about thirty pads, of note ...
- Every point on the yoke PCB (sorry not sure what this is called), and continuity tested, all OK
- Every coloured wire going to the AB
- Removed small grille on underside of AB and I suspect this is where the problem was - heaps of dust etc. Resoldered all the pads where wires went to.
Fired it up, and normal colour had returned! Although I'll need to recalibrate the monitor as I did play around with the pinchpots a little too much .... that's for tomorrow night.
Congrats on your repair, byrd!
FYI for recalibrating CC screens, I've found the Apple Service Manual invaluable. It's of course not difficult to recalibrate just by eye, but using the Apple Display Service Utility, and doing the adjustments in the order the Service Manual recommends, always produces a terrific image in just a few minutes.