Macintosh II - powers on immediately

[egrath]

Hi,

I have a Macintosh II here that I got as DOA. Recapped and cleaned everything, looks good so far. However, one issue remains:

The device powers on as soon as voltage is supplied to the power supply. Also Soft-Power-Off does not work.

Any hints on what I can check first?

With kind regards,
Egon

 

[blturner]

This writeup is the main reference I'm using for Mac II's with power issues: https://www.downtowndougbrown.com/2015/03/explanation-of-the-macintosh-iiiix-power-onoff-circuit/

Another great resource is over on TinkerDifferent by @David Cook https://tinkerdifferent.com/threads/macintosh-ii-advanced-diagnostic-techniques.5020/