68kMLA Classic Interface

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Colour Classic - identifying resistor
Posted by: macintosh2002 on 2023-07-11 12:54:33 Hello, I got a Colour Classic with working logic board (no battery damage, I replaced the caps, it chimes when you hit the power button) but the screen won't torn on. I replaced all capacitors on analog board too, and found a toasted resistor "RF19". Bomarc schematic doesn't include schematics of the analog board, so I need your help to identify this resistor please. Last picture is a from my working CC... Thank you Patrick
Posted by: ymk on 2023-07-11 14:08:48 4.7Ω
Posted by: macintosh2002 on 2023-07-12 08:55:05 Thank you, what performance should be used, 1W should be enough? Do you have a schematic of the this analog board?
Posted by: ymk on 2023-07-12 12:47:09 Nobody has produced a schematic as far as I know. 1W should be enough, but it doesn't hurt to go higher. Many of the parts in that area run very hot and the PCB is often scorched underneath. See this thread: Color Classic analog board trouble When I got this machine, the logic board had been fully recapped and the analog board partially recapped. The display and soft power both worked, but the picture was pinched horizontally in the middle, like an hourglass. The DL21 and DL22 18V zeners were cooked and burned the PCB around them... tinkerdifferent.com The hot parts are identified with links to larger replacements.
Posted by: pizzigri on 2023-07-14 03:02:06 Nobody has produced a schematic as far as I know. that is not correct, there was a reverse engineer attempt, that was not completed but still helps a lot: GitHub - pferronato/MacCCAB: Macintosh Color Classic Analog Board reverse engineered Macintosh Color Classic Analog Board reverse engineered - GitHub - pferronato/MacCCAB: Macintosh Color Classic Analog Board reverse engineered github.com
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