Astec PSU Question

[AwkwardPotato]

Do the Astec PSUs found in IIcx/ci/vx/Q700s have one of those notorious Rifa safety capacitors in them? I left one of these plugged in for about 10 minutes before there was a *POP* noise, followed by a loud whine and smoke rising from the machine. I assume these contain one of these caps but I'm a bit apprehensive about opening a failed PSU to see what went wrong. How long should I let it sit before it's safe to poke around inside?

Thanks!

 

[AwkwardPotato]

Decided to open the PSU anyways (it had been sitting, unplugged, for several hours) and yes, there are no less than 5 Rifas in this thing. Unsurprisingly, one of them had exploded, being the cause of the pop/smoke.

 

[AwkwardPotato]

Just wanted to ask before ordering new caps: is there any reason to recap these PSUs rather than replace them with modern ATX ones? Are the original PSUs reliable once recapped, or are they still failure-prone?

 

[68kMacx86]

Well, unless you take the time to rebuild that soft power circuit for the ATX, then your machine will remain on all the time controlled by power strip or switch on ATX.  funny you should have that issue

 

[nglevin]

The word was, specifically around the Macintosh SE/30, that the Astec PSUs were less reliable than the Sony PSUs. I can't really give you a good primary source around where that knowledge came from.

Of the PSUs I've owned for modular compact Macs, the Astec ones ended up running into problems powering on within a few years of occasional use. The Delta Electronics one I got second hand that was originally for a Power Mac 7100 has managed to stay in good shape for over six years and counting, knock on wood.

That could be luck, Astec being the more popular brand, and the nature of electronics decaying over time.

 

[68kMacx86]

One note

I thought capacitors were designed with that cross perforation at the top to gracefully vent when they failed, so they didnt pop and scare the crap out of cats, humans, etc.

 

[cruff]

Those Rifa filtering caps do not come in that form, which is typically used for electrolytic caps.  The ones that are failing have some kind of epoxy fill inside a rectangular plastic case, and it degrades over time which causes the problem.  It can be very smelly when they fail, with lots of smoke.  I had a dot matrix printer with one that failed, and I had to disassemble it, clean the case and let it air out in the garage it was so smelly.