Before I buy a new power supply for my IIsi, how can I test to see if my logic board is fried? When I plugged the power supply in once I heard some scary electricity noises so I wanna rule that out. Can I just touch two components together with a multimeter and if it lights up its good? (obviously two components that are connected by a trace)
How To Test Macintosh IIsi Logic Board
- Thread starter DontGetHit
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Unfortunately, the IIsi is notorious for leaky caps. The scary noises you heard were probably from caps past their prime. The IIsi i own I completely recapped but still crashes at boot. Might be a Ram issue. Hope yours treats you better than mine. 
Well I have recapped both the Power Supply and the Logic Board and they were both working for a week until the power supply started blowing fuses. The scary noises were with new caps as I never even tested the power supply before I recapped it. As for a RAM issue would a ram issue cause a problem of literally nothing happening when you push the power button? As if the computer is unplugged?Unfortunately, the IIsi is notorious for leaky caps. The scary noises you heard were probably from caps past their prime. The IIsi i own I completely recapped but still crashes at boot. Might be a Ram issue. Hope yours treats you better than mine.
Dang. Sounds like a power supply issue indeed. Maybe check out the board closely for shorts? That's about all I can suggest.
That's what I think but is there anyway I can test with a multimeter to see if the Logic Board got fried? Or is that pretty much out of the realm of possibility?
Almost positive it's your PSU I have 6 of these machines and three had this very issue even after a PSU recap
Alright thanks! Guess I'm just gonna have to bit the bullet and get a new one. Is it an extremely bad idea to take out the new caps I put in the broken one and use them to recap a new one?
Not necessarily, have you looked at that riser card in the PSU this is indicative of problems you may be having.
Yeah I did a close inspection of it the other day and from what I can see everything looks good. No corrosion, no gunk, its pretty clean. I did lift a pad on one of the caps but that is besides the point as it still wasn't working even before I did that. I did repair it though. From what I can find it is most likely a diode but I just do not have the skill to find out which one.
A couple of things to keep in mind. Has any of the UV mask been scraped away from the bottom of the power supply PCB by accident? A situation can arise where the metal case can come in contact with exposed traces and potentially cause fuses to blow.
Also, the IIsi uses the same power supply connector (and pinout) as the IIci, IIcx, IIvi & IIvx so if you have a working one of those floating around, you could plug the power supply into the IIsi board to see if it works.
Also, the IIsi uses the same power supply connector (and pinout) as the IIci, IIcx, IIvi & IIvx so if you have a working one of those floating around, you could plug the power supply into the IIsi board to see if it works.