Hi all,
Not so long ago I asked if I could put a Mac Plus logic board in side a 128k.
That was all good. Now I want to test a 512k logic board, but the 128k machine I was going to put it in has a suspected faulty power supply (it is making a frump frump sound with no bong or CRT lightup - suspect capactors!) So…I was wondering if putting it inside a Macintosh Plus housing and booting that would be feasible to see if the 512k board is okay?
Cheers,
Jeff
A Macintosh 512K board works fine inside a Macintosh Plus. All the connections are the same - as a matter of fact, installing a Plus board inside a 128k/512k housing with a replacement rear cover was an official upgrade option.
I replaced all the capacitors on my Macintosh 512K board for the same issue. While it helped, it didn’t fix the issue.
The problem ended up being dry solder joints on the Flyback Transformer. Once it was discharged, I went over the solder connections holding it to the Analog Board with a soldering iron. Very, very easy fix. Could be worth a shot. (Just make sure to discharge the Flyback with a CRT discharge tool first!)
Ah yes I’ll give that a try tonight thanks!
So that was a negative 
reflowed flyback, neck and Yoke connectors and same frump frump sound. I’m getting a 512k board shipped out to me so I’ll try that - as it could be a bad board