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Mac Plus is having repetitive power failures?

JNizzle

Member
I have a Mac Plus that has been working perfectly for decades, but it has recently developed a few issues. When the Mac boots, it will promptly reach the desktop as usual, but anywhere from 1-5 minutes after booting, the Mac will crash out entirely to a blank screen and replay the startup bong repetitively in no particular pattern until I shut the Mac down using the switch at the back.

When the Mac crashes, it will play the startup bong repetitively about 5-10 times and then it will somewhat restore itself and begin loading, only to crash out again during the startup process either before the happy mac or during the "wellcome to macintosh" screen.

This occurs when I boot the Mac from a floppy or drive. The power cable isn't at fault, I have used it with other Macs in the past and for them it seems to work fine. It makes no difference whether I'm using the Mac, or simply leaving it dormant, so I assume an old failing component is to blame.

I have checked the Dead Mac Scrolls for this issue, but it doesn't seem to be documented in there. I've breifly searched the internet, but haven't found anyone with this exact error yet. This Mac has only been used to demonstrate some vintage games and software, and has never had any upgrades done (besides a 4mb RAM upgrade, but I assume that was done years ago).

I haven't had the time to crack the Mac open yet, but I will get around to it sometime in the next few months.

Has anyone had this issue before, or at least seen a Mac with this issue? If so, what should I be looking out for when I eventually do the repair?

Thanks!

 

bibilit

Well-known member
I will say the optoisolator at U3. 

Notorious for becoming bad with years, I have changed a lot. 

 
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