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Apple Color Monitor IIc

H

Hjalmar

Experienced Member
Joined
Apr 28, 2022
Messages
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I'm trying to revive an Apple Color Monitor IIc A2M4043. I t was dead on arrival. It came with Samyoung electrolytic caps and some of them appear to have corroded through their aluminum cans. Never seen that before. I've replaced all of them with new caps and now all I get is a vertical line on the screen. Before it was just a dot. Does anyone have any experience with these monitors? I could use some pointers. I'm aware of the high voltage hazards. There doesn't appear to be any service info online. There's 16.406 KH audio from the board when it's turned on using Spectroid spectrum analyzer app on my Android phone. I assume from the flyback circuit.

Also have an Apple Color Composite Monitor A2M6020. It powers on then shuts itself down fairly quickly. I haven't had the cover off it yet.

Any insights or a pointers to a similar schematic.

Thanks
Todd
 
Last edited:
Update on the two monitors, they have the exact same chassis number. CHASSIS NO TWE CODE 3003-705-910

The same bad corroding Samyoung caps.
 
"I have not seen the inside of that model or a schematic but a couple sleepers - sometimes there is a service switch internal on the board to disable vertical to a line to do white balance adjustments, not
sure if Apple had that but easy to get bumped while working on the board. Another is the capacitor from vertical yoke to ground (if it exists) would be non-polarized and often mistakenly replaced with a polarized one.
The vertical IC would be a single row chip attached to a heatsink. It can develop cracked solder joints because of that.

Larry G"

I did see a switch and will try that. Another look for bad solder joints as well. I was aware that there are non polarized caps but none of the ones I removed appeared to be that way. It doesn't hurt to double check however.

Thanks for the pointers

Todd
 
I just noticed you said vertical line. You mean a line up and down ? Then it would be a totally different problem. The signal path would be the flyback drive thru the horizontal yoke then thru a width coil, maybe then thru a pincushion transformer to ground. Might not even be a cap in the path. Follow the path with an ohmmeter for an open component or trace. As far as the A2M6020 I'll attach a detailed hand drawn schematic (not by me). It shows the yoke paths I'm talking about which is a similar concept for many color CRT's.
 

Attachments

Thanks for all the help. I will dig into it some more when I feel a bit better. There should be enough here to get me on the right path.
 
Double check for capacitor leaks have caused corrosion of signal traces causing opens too.
 
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