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Macintosh LC II logic board troubleshooting

Challenger 1983

Well-known member
Long story short My LC II refused to boot one day and I suspected it was the power supply, after replacing the power supply the hard drive would spin up along with the system fan and the processor gets warm after awhile but no image would appear, there is no audio and no response to the keyboard or floppy drive, I recapped it and I’m now trying to figure out what other things could be wrong, I’m thinking it could be a bad Egret chip? Any ideas?

 

Fizzbinn

Well-known member
For those wanting to try something short of surface mount desoldering. I've had very good luck repeatedly spraying with flux remover (its stronger than plain IPA for dissolving gunk) and using a dental brush to clean the gunk out from under these chips. Got a Color Classic motherboard working this way (also did its sound chip like this).

4140A Flux Remover for PC Boards

https://www.amazon.com/gp/product/B07XDCRLR6/

DenTek Slim Brush Interdental Cleaners

https://www.amazon.com/gp/product/B009MHV3VW

These brushes can actually fit between the chip and its legs from either side. I kept working it and spraying more cleaner until the run off became clear, had the board propped up on one end with a bunch of paper towels on the other to soak up the run off (fun colors from the cap goo).

 

Challenger 1983

Well-known member
I removed and cleaned underneath of it, still nothing, however, now when i bridge some of the pins on the EGRET i get a sad mac chime so i think we might be getting somewhere

 

Challenger 1983

Well-known member
It however still will not boot or chime or show any signs of life, I think I’m about ready to give up on this motherboard

 
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