Diagnosing Macintosh Classic

[SpocksBeer]

It does that much without UA5 being present? Interesting I would not have expected that.

The variation in screen brightness may be down to electrolyte that has seeped into the PCB of the analogue board. It's quite porous and a real pain to deal with. Usually a deep soaking clean is required if this is the case - hot soapy water, or a ultrasonic cleaner if you have one

 

[DJ68K]

It looks like the "Screen" adjustment is overdriving the flyback. I suggest you adjust the brightness/contrast dials on the analog board. The Service Manual (page 89) has instructions on how to do this; ignore the light meter stuff (unless you have one) and adjust it so the non-lit areas around the sides of the screen (glass, but no image being projected) is as dark as possible.

 

[musawir]

will try the adjusting the dials and if that doesn't help i'll pull the boards out for another cleaning.

Any clues on the sad mac icon and the error code?

 

[Byrd]

Nicely done! I suspect cap goo is still present, have you checked the other culprits as noted TDA4605 @ IP1, CNY17G @ QP1, and diodes on the analog board, also clean the CRT adjustment pots and check voltages now showing life.

The Sad Mac: related to the motherboard likely caps or bad RAM; check again for cap goo, double check recap work and reseat the RAM, ROM chips (if socketed), electronic solvent cleaning spray on the sockets/slots helps.