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Thanks @nathall for the reply - Apologies for the late response, I missed the notification in my email. Will poke around a bit more. Thanks

Hi All, Bumping this back up again. Well I've had some more time to debug my Color Classic Mystic (575 + VGA Mod). 1. Audio works perfectly through the speakers and headphone jack, but there is a high pitched background hum/noise present through speakers. 2. The background noise/hum goes...

Thanks, this is very helpful. I kind of wish the issue was with the AB as that only has a handful of components... Where would you start troubleshooting on this board? Replace the main caps? I've heard of removing the DFAC, cleaning around and re-soldering. Thanks again.

Thank you, that makes sense to exclude the amplifier section on the AB. What would be the most promising culprit on the LB: resistors, capacitors associate with the sound circuit or the sound chip itself? Thanks again

Hi All, Last year I converted a Color Classic into a Mystic (575 + VGA Mod) and there is this high pitched squeal coming from the machine. I originally thought it was the flyback transformer, but it's actually the sound circuit. When I unplug the speaker or plug headphones in the noise goes...

Hi All. Anyone know what pin 21 does? I by mistake severed it while trying isolate pin 20. Is it a simple signal wire that I could use a bodge wire to fix or is it something more important that requires a thicker wire? Thanks in advance.

Thanks @olePigeon, I saw that thread but that method is quite a bit more involved than the one I’m trying. Besides, I have a Rev D board and its not totally clear what changes need to be made for that.

I found another site listing a very similar mod: https://www.micromac.com/instructions/CC_Video_upgrade/index.html which keeps the diode intact. Only difference with this version is that it connects pin 20 and pin 3 instead of 20 and 24. Any idea on which is "correct"? Thanks.

Hi All, I'm about to perform the VGA mod (Option 1) on a color classic analog board and ran across a discrepancy with my boards revision: My board doesn't have J78 so the instructions say I have to disconnect (isolate) pin 20. However, at DD1, there appears to be a diode (M5C) where in the...

I just tried 7.1 on a Zip disk with the system enabler and it booted just fine. So I’m assuming something up with 7.5.3?

Hi All, I picked up an LC575 motherboard to go with my color classic. I've done the software mod, using ResEdit modifying the boot process from 21->10 for gestalt id 99. This seems to have no effect as I'm always getting a bus error. I can probably rule out hardware error, since I've tried...

Oh yes of course, I meant either to part it out or sell it as is. Thanks

For some reason, I'm not seeing a whole lot of junker CCs on eBay...

Thanks All… at this point I may just cut my losses and dump it as I’m not seeing that characteristic trinitron line. 😞

Thanks! I’ll give that a shot. Any idea what these horizontal lines every ~ inch are?

Thanks. I hear the hum when turning the unit on so I assume the degaussing circuit is working. I bought a degaussing wand but it seems to have minimal effect aside from improving the initial “rainbow” picture to the one side green one.

Hi All, I’ve been able to open it up and have a little improvement in the picture. I don’t see anything obvious on the inside that is broken or missing. The tilt was corrected easily with a twist of the yoke. I’m having trouble with the color correction however. If I adjust the ring for red...

Thank you All! Once I crack it open I'll see what we're dealt with and report back with some pics.

Ahhh, gotcha... What have I gotten myself into? ha. When I saw the picture I had assume the color distortion was due to magnetic issue which could be solved with a degaussing wand/tool. Hopefully when I open it up I can see if anything looks out of alignment. Thanks

Thanks. Still waiting to have the unit in front of me, but you think based upon how much the picture is skewed, the Vertical Angle (PR) adjustment won't help?