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

[ThisDoesNotCompute]

I was handed a pair of IIsi power supplies, Sony APS-06, 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?

 

[imactheknife]

I was handed a pair of IIsi power supplies, Sony APS-06, 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?

I hate the iisi psu, well just the sony one. Just recapped one and works great, but how many have not is crazy.. they are frustrating little turds. No idea of anything more than recap either. Good luck!

 

[JC8080]

How bad was the corrosion from leaking caps? I had one with quite a bit of corrosion, I recapped it and it worked fine for a while, then failed. I opened it back up and found one very questionable trace which I then repaired, and then I scraped away the big patches of corrosion down to bare copper and covered the bare copper in a layer of solder, it has been working fine now.

 

[croissantking]

Worth looking the PCB over for dry joints. Mine had quite a few. Could it be something like that?

 

[joshc]

The Bomarc schematics include the schematics for the Sony power supply.

If there’s no start at all one of the ICs on the soft power side of the power supply could be to fault if too badly affected by capacitor goo.

 

[JC8080]

Worth looking the PCB over for dry joints. Mine had quite a few. Could it be something like that?

Ah yeah I forgot to mention that in my post. I reflowed all solder joints, and some of the large ones were visibly cracked.

 

[bibilit]

Corrosion components can be found in very awkward locations.

Had one with bad resistors which were hidden under a transformer, where capacitor fluid had found it’s way.

Both were corroded so bad, they simply fell apart. Replaced both and the PSU turned on.

 

[ThisDoesNotCompute]

Does the little vertical daughterboard control the standby voltage? There was some leaked electrolyte when I recapped it, but I cleaned it as best I could. Perhaps it needs a trip through the ultrasonic? The main PCB had already been recapped when I got the PSU, and didn't look too bad, but it's entirely possible that some leakage wasn't cleaned up there.

 

[croissantking]

Does the little vertical daughterboard control the standby voltage? There was some leaked electrolyte when I recapped it, but I cleaned it as best I could. Perhaps it needs a trip through the ultrasonic? The main PCB had already been recapped when I got the PSU, and didn't look too bad, but it's entirely possible that some leakage wasn't cleaned up there.

Did you check over the main PCB recap job just to make sure nothing silly was done e.g. capacitor the wrong way around?

 

[ThisDoesNotCompute]

Funny enough, the first of the two PSUs I fixed did have a cap that was reversed. Replacing it got that one working perfectly. This second unit didn't have that problem.

I think the next logical step is to throw the daughterboard into the ultrasonic cleaner, then try to clean the DC side of the main PCB as best I can. The idea of cap leakage having gotten under other components is a likely one.

 

[croissantking]

I went a bit overkill on my PSU when I serviced it. Between all the cracked joints and leaked electrolyte, I decided to desolder every single component.

I tried to repair the solder mask but made a bit of a mess of it. Hopefully, my next attempt will be a bit better.

The PSU powered on OK before doing this work, but I only tested it to chime. It's rock solid now.

 

[jmacz]

The PSU powered on OK before doing this work, but I only tested it to chime. It's rock solid now.

Nice!!