Mac SE FDHD - Repeated resetting on cold boot

[blusnowkitty]

I picked up a Mac SE the other day (yes, that green SE) and it worked when I first got it but now has an issue on cold boot. See the attached video for a better idea, but basically when it's cold it will sort of start up, and then immediately power-cycle and it will do this until something warms up and stabilizes inside. While it's powercycling it is able to power the CRT and you can see garbage data on the screen. +5v and +12v are rock solid and don't appear to be affected during the powercycling nor does it make any difference whether the hard drive is plugged into power or not.

All that said, I have noticed it makes a strong smell inside the case like my Quadra 610 and Mac Portable made when I was replacing their leaky capacitors. I'm gonna guess I have bad capacitors on the analog board or the PSU? Or is there something else at fault here? This SE has lived a hard, rough life; there's rust on the motherboard DB connectors and a few of the traces have corrosion on them.



View attachment IMG_2836.MOV

 

[Bolle]

Caps in the power supply.

It looks like at least the 5v supply is fluctuating. If you have a digital voltage meter it may not pick up the voltage changes quick enough and just show 5V instead.

Got an analog meter or a scope? You’ll see the voltage is breaking down with either of those.

 

[blusnowkitty]

That's what I was thinking. Unfortunately no scope or analog multimeter here. I also started noticing some flicker/instability on the CRT so I suppose I'll recap both the PSU and analog board.