Macintosh 128k keeps restarting

[Mac128k]

Hello everyone I have a Macintosh 128k with a 240v analogue board that keeps restarting after running it for about 10 minutes but it mainly does it when the speaker is in use like when playing a game or something. I think it has something to do with the flyback as a failed one can cause speaker interference but I have never heard of a flyback restarting the machine though could this be something else causing it or just the flyback. And just to clarify I have tested 3 different motherboards that work fine with other machines and they do the exact same thing so it has nothing to do with the motherboard.

 

[bibilit]

Analog board issue, probably struggling to get to the right voltage and rebooting (when the floppy is in action)

Can be a problem with the Optoisolator, which is part of the regulation side.

 

[Mac128k]

Thanks I also just turned it on with the lights off and the flyback has cracked as I can see the blue arc I have seen people use electronic silicone to repair the cracks on flybacks does this actually work properly.

 

[joshc]

I would say at this stage you should seek a replacement flyback, the best place to find one is from a spare analog board - they come up on eBay now and again.

 

[Mac128k]

I do have an old flyback transformer on a blown up 120v 128k analogue board that was given to me by a mate but the analogue board that is in my 128k is a 1986 240v replacement one as I think the original must have fried out and had to be changed out.  Its just a matter of weather a flyback from 120v board will work on a 240v one.

 

[Mac128k]

What's the best replacement for the optoisolator as I have looked around and replacement part numbers can differ.