Classic Mac II Power supply issue

[pme]

Hi,

I have purchase an old classic mac

I have recap logic and analogic (ref 820-0525) boards, replaced IRF BC40, TDA4605 and CNY17 (opto), diode dp3, dp4, rework connectors solder,  but +5v still weak (start at 4.65v) cold boot doesn't work.

If i use a hair dryer a little on analogic board, +5v increase till 5.1v (keep stable) and boot is ok.

Any advice to find the issue ? I'm out of idea.

Thanks in advance

 

[dochilli]

Turning pp1 a little bit could be a solution, but measure the 12V while you turn pp1. Check the voltages for the next minutes, if they are stable.

Sometimes the potentiometer needs some turns and works again afterwards.

 

[pme]

I've already tried PP1 but not solve the issue PP1 at max give 4.81v 

 

[OsvaL]

Did you solve this issue? I have the exactly same problem with my Macintosh Classic. It will only boot when I use a hair dryer to heat the analog board (already recapped). When I test the rails from the hard drive power supply I get a steady 12V and 5V respectively without using the hair dryer. When using the 12V goes up to 12.3V

If I turn the potentiometer a little bit the voltage increase up to 13V but it doesn't fix the problem. Only the hair dryer does it.