Oh hey, it's another dead IIsi power supply thread

[This Does Not Compute]

I was handed a pair of IIsi power supplies to try to fix. One of them was easy to get working again, but the second is being stubborn. It's been fully recapped (including the SMD caps on the daughterboard), and it's producing the 5V standby rail. A known-good IIsi won't power on with it installed (but will with 2 other PSUs)...just no signs of life whatsoever (speaker pop, fan spin, etc). Since I get the standby rail I think it's clear it's something on the secondary side, but I don't know enough about switchmode PSUs to be able to troubleshoot much further on my own. Anyone have ideas?

 

[joethezombie]

You can check for gunk under the fixed inductors spread amongst the capacitors. I was lazy and didn't pull them up, believing a simple alcohol irrigation after removing just the capacitors would be enough, but it wasn't. There was so much cap gunk stuck under those chokes, it prevented the power supply from startup. After removing and cleaning the area properly, it worked.

Another issue I had on another unit, the daughterboard traces had been compromised, requiring some rework. Check it closely for corrosion. Good luck!

 

[YMK]

I just received my first IIsi, minus PSU, so I don't know anything about them.

I do know that it'll happily run from a 12V ATX PSU fed from a 1A wall wart, so that's how I'm setting mine up.

Without a spinning HDD, the draw from the 12V input is 800mA, under 10W total. No need for a fan.

 

[Garrett]

I’ve also had many frustrations with the Sony IIsi units, although my issues were different than yours. Most of the time I have the problem of them remaining “on” and not powering down. My recent discovery for that problem was a very thorough cleaning in IPA. Seems the conductive cap juice persisted in some places it shouldn’t. That might work here too? Could be worth a shot if you haven’t tried soaking everything.

Also echo the comment on the daughter board, those tend to be particularly nasty. I usually have to remove the large Mitsubishi chip in order to properly clean everything. Good luck!

 

[This Does Not Compute]

Yeah, I think the approach at this point is going to be throwing the daughterboard in the ultrasonic cleaner. I *might* be able to get the DC side of the main board in there too if I'm lucky. The PSU came to me with the through-hole caps already replaced, and I suspect there wasn't much cleaning done.

 

[XKSTEVE]

Same here. Had a faulty recapped mac LC PSU sent in for repair and cap juice was under the ICs and the inductors but after a clean and reinstall of all the components worked fine.

Hope yours is the same simple fix.

 

[3lectr1c]

Same boat... Got mine already recapped and was working fine, then it shut off one day. Will start with the hard drive unplugged still, but even then makes a whining noise, and won't stay on with the hard drive. If I'm lucky I'll get as far as a chime before it shuts off again. I hope it's just some left over ELNA crud.