So I have recapped a few power supplies for older 32 bit Suns (ex: IPX, SS20) with success. No odd behavior, machine works as expected. However the SS10 PSU (Sony APS-39, SUN 300-1081/300-1255) is giving me fits. I have 3 total of these, and out of them only 1 seems to result in a stable machine. The behavior is quite strange - the machine panics right at soft shutdown/powerdown. After troubleshooting nearly everything else in one of my systems, I finally figured out that the problem follows the other 2 PSUs and there is 1 “good one”. All 3 PSUs “work” in the sense of the machine powering on and running. It’s just at final poweroff/shutdown that 2 of the 3 result in a panic.
It seems like the issue could be some (non-electrolytic capacitor) component that’s gone bad in two of them, but not the “good” one ? If this is the case - what component(s) would you all recommend looking at next ?
I don’t think that looks too exotic. Anyone have an idea of a modern alternate PSU that I could adapt to this ? I’m willing to sacrifice the wiring harness to build a replacement if possible.
Holy moly - that’s literally the kind of thing I was looking for. Looks like you hit a wall at the end though. Did you ever get this working ?
Seems like this PSU has just enough quirks to make it close to a fools errand to replace
I did manage to get the main PCB of the APS-39 separated (lots of desolder gun work) and everything recapped. But like I said - it seems like there might be some other component that’s failed and I don’t know what to look at/test next…
EDIT: I see that you actually did get it working. If I were to try to undertake this would you be willing to go back and forth in email for any help ? I can certainly make a dontation to you or charity of choice. Thanks.
So I pulled the trigger and ordered the parts. Working my way through.
I have the original PSU chassis gutted and I’ve 3d printed a nice mounting plate for the inside. I’m reusing the AC input on the back and routing this up to the NV1.
The fan rerouting to make socket 4 the input works great. I can give it 12V and the fans go full blast.
The first stumbling block I’ve hit I wasn’t expecting at all. My fan voltage drop resistors run “crazy hot” (yes a very scientific unit of measurement).
I used 2 x 15ohm 2W 5% resistors in parallel. The wire to get from the fan PCB up to the resistors is 22awg solid. I didn’t think this would matter, obviously I could be wrong. I get 7.5 ohms reading the pair and the voltages on the fans are around 9v. But like I said, after a minute or so I can’t touch the resistors
Any ideas on this ? Worst case I can just shunt the wires together and run at 12v full blast but I’d really like to follow what you’ve done.
Quick calculation says you would be dissipating a bit more than 1W (that is, 3v squared over 7.5 ohms). So, a bit over half the resistor rating - some advice would suggest a higher-rated resistor at that point. If it’s too hot to touch, that maybe is a bit too hot. Some sources suggest a higher-rated resistor will run less hot - if it’s bigger it has more surface area, maybe that’s why. Watch out for the heat damaging nearby things too.
Thanks for the reply. I think I’m actually just going to attack this a different way - replacing the stock fans with nice quiet Noctuas. I actually had 2 of the 3 I needed laying around from a past shelved project - so I just ordered another to complete it.
EDIT: It was implied in my head, but what I meant to say was these will run dumb/hard at 12v. They are so much quieter and I do believe they move enough air.
So I fired this up - and I hit the same issue you did when troubleshooting the sense lines:
My machine beeps, power LED comes on, but then goes off a few seconds later and nothing…
The sense wires I am using are 24awg from some cat 5 cable. I’m thinking these are too thin ? I did twist them (using a drill) even more than they were already twisted.
Assuming this is my issue - would something like 20awg copper work ? If this is the issue, this seems very very sensitive.
I also verified (and made a small adjustment to get it there…) that the voltage at the SS10 connector is 5.10 dead on. I have some super thin needle probes I got into the 18pos connector and was watching as I hit the power switch. 5.10 the whole time.
Thanks.
EDIT: Forgot to also ask, why the pin no. twice (in parentheses offset by -1) on the SS10 side:
Was this a first draft error ? The pins in the parentheses seem correct as they match up to the Sun documentation on the APS-39:
Now it beeps, power LED stays on, but drive doesn’t power up. I’ll do some invesitgation to see if the drive somehow died in a huge coincidence right as I was testing all this.
