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Everything posted by theorime

  1. Hi everyone, I just bought a Macintosh Classic from 1991. When I turn it on, I have to wait for a few seconds/minutes to make it startup (probably due to the analog board capacitors), but then I have the checkerboard screen issue with a wobbly image. I washed the motherboard with solder flux cleaner, and then changed the capacitors, but it had no effects. So I have a few questions : - Can the lack of battery cause this issue ? I couldn't find a suitable one for the moment - I did not change the analog card capacitors, could it be the reason ? - What are the expected voltages on the analog board to motherboard cables ? - Do you think solder flux cleaner is not enough to wash the board ? Should I use water and soap ? Thank you very much !
  2. theorime

    Macintosh Classic Checkerboard screen

    I finally found the problem ! After cleaning the logic board, replacing the capacitors on both boards and two diodes on the analog board (as suggested by @bibilit on another thread), still nothing worked. My voltage was a little bit better, but still not enough. So I changed the CNY75GB optocoupler, and now everything works perfectly fine ! Thank you all for your help
  3. theorime

    Macintosh Classic Checkerboard screen

    Thank you all for your answers ! I washed the board with soap and water, but still no results... On the motherboard, I have 3.6V or 9V, but never 5V or 12V. Maybe the analog board doesn't deliver enough voltage to make the motherboard works properly. I think i'll try to recap it. What could be the problem on the RAM, and how could I check it ? About the ROM, I have to admit that I'm scared to remove it. Is there a special technique to do so ? I'm trying to pull it raw but it doesn't move even a little bit