SV25 "Achme" PSU - Deaded

[SlightlyMiffed]

Shuttle SV25 ACHME PSU - 150w

Greetings

I have two SV25's returned to me with dead PSU's. (No power at all)...

Opening them up I could see the green "Teapo" caps (1000uf 10v) are all leaking/bulging so I've replaced these with brand new caps of exactly the same rating.

Unfortunately, the units still don't power up...

All the other caps in the PSU look ok so I wondered if anyone has any experience with these PSUs and any suggestions what to do with them next!
(or they are heading for the bin)..

Thanks in advance

[AK0R]

Re: SV25 "Achme" PSU - Deaded

What did you use for replacement capacitors? They need to be high-quality, low-ESR capacitors (as described in numerous places elsewhere on the site); parts typically found at Radio Shack or the like are not adequate for the job.

Unusual to hear about Teapos failing with evidence of bulging and leaking; they usually fail without any outward indication.

[SlightlyMiffed]

Re: SV25 "Achme" PSU - Deaded

Thanks for the reply.

I replaced the 1000uf 10v's with these:
http://uk.farnell.com/jsp/endecaSear...SKU=768406&N=0
which I had lying around from a previous project. Not sure now if these are suitable or not...

The Teapos I've removed are definately bulging.

[Chris1992]

Re: SV25 "Achme" PSU - Deaded

They're rubycon ZL, good caps and long life.

[SlightlyMiffed]

Re: SV25 "Achme" PSU - Deaded

Thanks Chris, at least I haven't completely messed it up!

There are a couple of other caps in the PSU I haven't replaced as they look ok.

1 x "Vent" 680uf 16v
1 x "Vent" 470uf 16v

There are also 2 x "Teapo" 1000uf 10v (I think - pretty hard to see) which are smaller than the other green "Teapo" ones I've replaced.
These look fine and don't have the bulging tops like the green Teapol ones I've removed... but I may try replacing these to see if it makes any difference...

[Rainbow]

Re: SV25 "Achme" PSU - Deaded

Something else probably went bad when the caps failed. Check transistors and diodes for shorts and also check the fuse.

[PeteS in CA]

Re: SV25 "Achme" PSU - Deaded

Unfortunately, the units still don't power up...

This is probably a stupid post, but did you try to power up the P/Ss stand-alone? Or with the P/Ss plugged into the MB? Modern PC P/Ss turn on using logic on the MB and won't turn on unless plugged in (or you ground a certain pin on the ATX connector). A decent test to see if the P/S is dead is to check the +5V Standby O/P. If it's gone, you probably have a blown fuse (and fuses blow for "good" reasons).

[tiresias]

Re: SV25 "Achme" PSU - Deaded

Unfortunately, the units still don't power up...

Hi SlightlyMiffed,

What exactly do you mean by "not powering up"?

If you have time, perhaps you could take a few really simply "preliminary checks" to try to establish if there's a relatively easily fixable fault at one of the "early stages" in the PSU, or such things as loose PSON wires:

1. Is AC power even reaching the PSU's PCB contacts? (Initial wiring)
2. If so, is the fuse OK?
3. Do the input capacitors charge? (Check this with your multimeter set to 500VDC or so)

If you can answer "yes" to all these, then at the other end...

1. Is there a 5Vsb?
2. What about a 5-volt-like difference between PSON and ground?

Yes to both? Short PSON to ground. Then:

1. Do we still have a 5Vsb or has the unit now shut down?
2. Are there any DC outputs (3.3, 5, 12, -12)?
3. Are the output capacitors charging at all?

Let us know.

[kc8adu]

Re: SV25 "Achme" PSU - Deaded

seems these have a 330k or so resistor that opens and renders them dead.
comes off the main filters and goes to a 15v zener to make b+ for the pwm chip.at least thats what is coming to mind at the moment.
dont toss these units if you give up.
i like those shoebox pc's.send em my way!

[PeteS in CA]

Re: SV25 "Achme" PSU - Deaded

Good point, kc. That resistor, a small 'lytic (probably 47uF or 68uF), and the zener provide start-up bias to the PWM. After start-up, there usually is a winding from the main transformer that "takes over" and provides bias for the PWM. If that resistor or the cap opens up the P/S main inverter won't turn on.

[arneson]

Re: SV25 "Achme" PSU - Deaded

Thanks to you both, I deal with some Shuttles that are very hot and this is good info.

[SlightlyMiffed]

Re: SV25 "Achme" PSU - Deaded

Yes, thanks guys!

Plenty for me to be looking into here.
Power supplies aren't really my thing, but the info here will help greatly!

Cheers

[RJARRRPCGP]

Re: SV25 "Achme" PSU - Deaded

The bulging green caps probably weren't Teapo. They don't seem to ever fail. Or at least visibly!

[SlightlyMiffed]

Re: SV25 "Achme" PSU - Deaded

PeteS:
No, not a stupid post, but I was aware the ATX powersupply won't power up on their own. I test them using an old motherboard all wired up. A good power supply powers on the little green led on the motherboard, and fires up when I power on.
These Achme units do nothing...


tiresias:
1. Yes. AC power if going in.
2. Fuse in the plug...? then yes.
Is there another fuse on the board or something ? (I've come across amplifiers with onboard fuses, but can't see anything that looks like a fuse inside the power-supply).
3. Nope.. none of the caps charge.

kc8adu:
I would be happy to send you the units, but I think the postage to the US might be a bit much. (I'm in the UK)...


RJARRRPCGP:
The caps were clearly marked "Teapo".
The leaking I saw could well have been the glue stuff they seem to pour onto the components, but the top of each of the caps was not level - If I put them up-side-down on a flat surface they wouldn't sit level and wobble about. Unfortunately I've binned them now or I'd upload a piccy...


On one unit I have noticed a "blacken" resistor (I think its a resistor anyway) on the small daughtercard. Its labeled "ASD1"...
Not sure if this happened after re-capping or it was like it previously, but looks pretty tricky to replace.


I've probably wasted enough time on these now and am out of depth, but thanks for your help guys! Without this site the shuttles would have been dead a year ago (had to re-cap the motherboards when they died).

Cheers!

[tiresias]

Re: SV25 "Achme" PSU - Deaded

A good power supply powers on the little green led on the motherboard, and fires up when I power on.
These Achme units do nothing...

From which you can conclude that the the +5Vsb (along with the rest of the outputs, in view of the non-charging input caps) isn't there.

Fuse in the plug...? then yes.

Those "good old" British plugs! (I'm from the UK myself, actually, albeit 'emigrated', due to wife & co. to this small, absurdly densely populated, country, situated well below sea level)

I was actually referring to the PSU's own fuse. Every PSU I've seen has one, usually wired just after (or almost just after) the AC inputs to the PCB. Admittedly, though, it's not always easy to find - I've seen them sometimes shrouded in black heatshrink for some less-than-obvious reason.

I've probably wasted enough time on these now...

I certainly can relate to that feeling...

But in any case, good luck with your other hardware endeavours.

[SlightlyMiffed]

Re: SV25 "Achme" PSU - Deaded

Those "good old" British plugs!

I forgot that the rest of the world doesn't go in for fuses in the plug!

I was actually referring to the PSU's own fuse. Every PSU I've seen has one, usually wired just after (or almost just after) the AC inputs to the PCB. Admittedly, though, it's not always easy to find - I've seen them sometimes shrouded in black heatshrink for some less-than-obvious reason.

Bingo! - There is indeed a fuse wrapped in black heatshrink (I was wondering what that was)... Quick test shows its dead so I'll replace it with ..um.. something more solid to see if that helps any!

[SlightlyMiffed]

Re: SV25 "Achme" PSU - Deaded

I replaced the fuse with something similar I had, slightly higher rated. It blew straight away so did another even higher rated.. which kind of suggests bigger problems to me.

Worth a punt though I thought!

Thanks tiresias (and everybody else)... I'll now leave it at that and try to find some replacements.

Cheers

[Rainbow]

Re: SV25 "Achme" PSU - Deaded

Main switching transistor is probably shorted (or something in auxiliary supply).

[linuxguru]

Re: SV25 "Achme" PSU - Deaded

Check the MOVs across the primary caps - these will usually fail shorted on a voltage surge. If these are OK, the next suspects are the primary bridge rectifier, and then the primary switching transistors.

[kc8adu]

Re: SV25 "Achme" PSU - Deaded

its not good to overfuse.likely to cause even more damage.its self limiting though.foil will blow if fuse is too big...