Mac IIci blowing electrics (even after PSU recap)

[LazarusNine]

The mind boggles. Bought a Mac IIci. Plugged it in and turned it on and it blew the ground floor circuit in the house. Tried in different plugs. Same result.

Tonight, I recapped the motherboard and PSU, switched the computer on and after a handful of seconds, it blew the electrics in the house again.

Does anyone have any idea what is occurring here? Might a new PSU be necessary - or something else? It's worth mentioning that the computer seems to boot just fine! =P

 

[aladds]

Tripping an RCD/GFCI? That would be a short/low resistance between live and earth. If you've got a multimeter you should be able to find which conductor pin is the culprit.

The worry, of course, is how this has happened. I'm guessing one of the Y capacitors has failed.

I don't have a schematic of the IIci PSU, but here's a generic page showing how X and Y capacitors connect across the power input: http://thejourneymanwizard.com/2015/02/04/capacitor-parameters/

If it only happens when the computer is on, it's possible there's something like this on the power output, too, as that will probably have similar noise suppression.

Remember usual precautions when working inside a PSU. Namely, don't have it plugged in

I would guess that a new PSU would also fix this if you'd prefer not to open it up and fix it (and I wouldn't blame you!)

 

[Unknown_K]

I would say a short in the power supply before the fuse.

 

[LazarusNine]

Yeah, I just yanked my Quadra 700 PSU and put it in the IIci. Everything worked fine. So, it's likely a short somewhere. I just spent about £15 on new capacitors for that PSU as well... Oh well. I might just source another PSU.

Am I correct in thinking the 7100 PSU works in the IIci also? I've seen this suggestion on various other threads, etc. What I should really do is figure out how to hack an ATX PSU into that case - seems daunting, though!

Thanks for the responses so far.

 

[rsolberg]

If you haven't seen significant smoke, my guess is an AC inlet wire pinched on the chassis, or the hot end of the fuse touching the chassis somehow.

 

[360alaska]

This might be an odd question but do you have any idea if it's afci or gfci breaker? Have you metered the input of the ps with a ohmmeter to see the transformers resistance?

 

[techknight]

Its the X1/X2 safety capacitors. Common problem. You will have to pop it apart to figure out which version of safety capacitor it is, and replace it. Or remove it, but it wont have neutral/line/ground safety anymore. 

 

[MrGasS27]

My IIci had same problem, I replaced original PSU with an ATX and now works like a charm.

 

[LazarusNine]

My IIci had same problem, I replaced original PSU with an ATX and now works like a charm.

Perhaps I'll have to pick your brain about this at some stage, as I'd have preferred to replace the PSU with ATX instead of buying a PSU from a 7100 (which has worked well). This was all after replacing all the caps in the original unit!

 

[techknight]

Like I mentioned, you missed the X1/X2 safety capacitors. if you would have caught and changed those (boxy caps, not electrolytics), it wont trip the breaker anymore.