Hi mates,
I have an analogue board from a Mac Classic that wasn’t working. There was visible corrosion from a leaking capacitor, but it seemed fairly isolated.
I’ve now replaced all the capacitors, and I’m getting a steady 5V and 12V from the Molex connector with the digital board disconnected, but:
when I connected the digital board and powered it on, I saw the checkerboard pattern, and then it started boot cycling — the warmer the board got, the more stable it seemed.
I noticed the 5V rail was dropping below 4.85V, so I adjusted the variable resistor near the optocoupler until I got a clean 5.2V with the digital board disconnected.
Now, with the digital board connected, it boots up and I get a steady 4.98V, and it can even boot from BlueSCSI. However, it still randomly restarts when the voltage drops to around 4.86V — or maybe it's restarting for another reason and the voltage drop is just a side effect. Not sure.
I know the digital board is fine because it works perfectly in another healthy Mac Classic.
I’ve already reflowed all the solder joints in the video and high-voltage sections of the analogue board.
At this point, I’m stuck. I don’t have the skills to go deeper with diagnosis or pinpoint which component might be failing.
Any suggestions on what to try next?
Happy Easter to those who celebrate, and best wishes to everyone!
I have an analogue board from a Mac Classic that wasn’t working. There was visible corrosion from a leaking capacitor, but it seemed fairly isolated.
I’ve now replaced all the capacitors, and I’m getting a steady 5V and 12V from the Molex connector with the digital board disconnected, but:
when I connected the digital board and powered it on, I saw the checkerboard pattern, and then it started boot cycling — the warmer the board got, the more stable it seemed.
I noticed the 5V rail was dropping below 4.85V, so I adjusted the variable resistor near the optocoupler until I got a clean 5.2V with the digital board disconnected.
Now, with the digital board connected, it boots up and I get a steady 4.98V, and it can even boot from BlueSCSI. However, it still randomly restarts when the voltage drops to around 4.86V — or maybe it's restarting for another reason and the voltage drop is just a side effect. Not sure.
I know the digital board is fine because it works perfectly in another healthy Mac Classic.
I’ve already reflowed all the solder joints in the video and high-voltage sections of the analogue board.
At this point, I’m stuck. I don’t have the skills to go deeper with diagnosis or pinpoint which component might be failing.
Any suggestions on what to try next?
Happy Easter to those who celebrate, and best wishes to everyone!
