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PSU problem

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First post, by obcbeatle

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Hello ... while I wait for some jumper wire I just ordered ... I thought I’d start another project.

I have a power supply unit (PSU) that when I turn on the PSU power switch ... the PSU fan momentary spins (with no noise .. it spins so briefly) and then stops spinning. This is when the PSU is not connected to the motherboard (mobo). I removed the PSU case and blew air through the PSU to clean out the dust, etc and inspected. Nothing jumped out at me visually. So I used a paper clip on a black ground wire and the green wire and the fan spins normally. I then checked the voltages of all the pins on the ATX 20 pin connector that connects to the mobo. ... all pins were within voltage tolerances. I also checked the separate ATX 4 pin connector pins that are on this PSU ... and that I believe is normally connected to the mobo for the CPU or a graphics card. All voltags were within tolerances. There is no 4 pin ATX connection on this mobo ... an ASUS A7V333-X ... (or on the original graphics card ... an AGP card). So I’m not sure why that seperate 4 pin ATX connector was included on the PSU for this mobo ... unless that was just normal for PSU’s back in the day. When I connect the PSU to the mobo to put a load on it the PSU behaves exactly the same way as when not connected to the mobo (very brief fan spin when powered on ... then the fan stops). I added the some RAM, a FDD, a HDD, keyboard, etc to give the PSU more load ... and still the same behaivor. In fact ... the CPU fan mimics the PSU fan when I turn the PSU power switch on (very brief spin ... then stops). The mobo LED light glows (and remains on) when the PSU power is on. The PSU is original to this mobo ... and this PC used to work a few years go.

So I think there is a problem with the PSU. What would you do next to try to verify or isolate the PSU problem? Any tips or suggestions appreciated. Thank you.

Last edited by obcbeatle on 2019-01-11, 18:53. Edited 1 time in total.

Reply 1 of 16, by Nvm1

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I can see 2 blown caps in your PSU, so unless you change them the PSU is a no-go to be used at all..
In the second pic between the blue cables and the alu heatsink you can see them, on pic 3 you see one of them with a blown open top..

Reply 2 of 16, by obcbeatle

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Thanks for the quick reply Nvm1. What would normally cause PSU caps to blow like that? And/or what else might I check to understand WHY they blew ... before I go to the trouble of buying replacement caps to install myself? Or do PSU caps commonly fail in computer PSU's because the original caps were cheap ... for example? Just curious. Thanks again for your quick reply and detection ... much appreciated!

Reply 3 of 16, by elod

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Just replace those caps. They are most probably for the 5V standby, they also fail first in FSP units.
They go first because when plugged in they are working non stop. And they are also cheap, crap caps.

Another point: do not trust that PSU, replace with a well known ATX v2.3 unit as soon as possible.

Reply 4 of 16, by obcbeatle

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OK ... thank you for the replies and assistance. I think I'm inclined to just replace the PSU. One last question ... this PSU/mobo have 20 pin connectors. I believe ATX PSU's are now standard 24 pin. So my main criteria for buying a new or used PSU would be to find one that is a ATX 20 pin 350W PSU ... correct? Thank you in advance.

Reply 5 of 16, by gdjacobs

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If you're interested in powering an older machine (like a socket A), you generally need more capacity on the +5V rail. That either means a ridiculously powerful modern PSU, a good condition used unit, or something new which is still ATXv1.3 compliant like a Startech (https://www.newegg.ca/Product/Product.aspx?It … =9SIA7BB2ND7201).

A P3 unit is much more forgiving, and a P4 uses 12V for CPU power (although watch out for some that have weird aux power connectors).

All hail the Great Capacitor Brand Finder

Reply 6 of 16, by obcbeatle

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OK ... thanks for the info. and reply. And the link. I had no idea PSU's could be so expensive. But I get that the PSU is a such a critical part of the computer. I remember replacing a server PSU back in the day. What a hectic day that was ... trying to find a replacement and install it within a couple hours. I spent a lot of time and effort researching those servers. But the one thing I didn't take into account was redundant power (dual PSU's). The things you do when you're young 😀 I learned the hard way. Bosses/users don't like it when servers go down. Oh well ... live and learn 😀 Thanks again!

Reply 7 of 16, by SirNickity

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Typically a server -- at least one in production, at a business where somebody gives a crap about IT -- will have a service contract. When the PSU fails, you call Dell / HP / IBM / Cisco and say "I lost a PSU, please have another here by EOB today." Then you go to lunch, and by the time you get back, a courier has dropped off a box at your desk. The redundant PSU has carried the load this entire time, so you slide in the replacement, redundancy is restored, and nobody is aware anything out of the ordinary has happened at all. 😀 The same goes for disks and fans.

Regarding 20-pin ATX connectors, it's not always a big deal. Many ATX supplies have a 20+4 connector. If you have a 24-pin motherboard, the connector slides on as one piece. If you have a 20-pin motherboard, the 4-pin extension clips on to the end of the 20-pin connector and can be easily removed. Failing that -- if it's one single 24-pin connector -- you may be able to use it anyway. The first 20 pins are the same, and can be connected to a 20-pin socket as long as there's nothing interfering (caps, inductors, etc.) on the +4 end. Failing THAT, you can get a 24-to-20 adapter or just a 20-pin extension cable (which, again, just fits onto the first 20 pins.)

I would agree the supply in question doesn't appear to be the highest quality supply ever, but it's probably ... alright ... enough. It needs a complete re-cap. Any supply old enough to have a stout 5V rail probably does, but yours especially if it has already lost a few caps. Whether you trust its build quality after restoration is a personal choice. You'll never know when it's going to fail, or how controlled that failure will be, until it fails... so there's always some degree of risk. I once spent a handsome sum for a cream-of-the-crop PC Power & Cooling supply, which failed less than a year after purchase. Meanwhile, I have a couple cheap OEM AT supplies that STILL work. It's a total crapshoot.

Reply 8 of 16, by elod

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PSUs can be extremely cheap. We (Romania) are flooded with OEM PSUs for the "hefty" price of about 5 bucks.
If you buy new 50 is about where they are getting ok.

Reply 9 of 16, by gdjacobs

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elod wrote:

We (Romania) are flooded with OEM PSUs for the "hefty" price of about 5 bucks.

This is believable. In my experience, Gutless Wonder PSUs are usually light enough to float on water. The next "upgrade" is usually where they throw in fake components made with steel, lead, or concrete to make it seem more substantial.

All hail the Great Capacitor Brand Finder

Reply 10 of 16, by obcbeatle

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SirNickity wrote:

Typically a server -- at least one in production, at a business where somebody gives a crap about IT -- will have a service contract. When the PSU fails, you call Dell / HP / IBM / Cisco and say "I lost a PSU, please have another here by EOB today." Then you go to lunch, and by the time you get back, a courier has dropped off a box at your desk. The redundant PSU has carried the load this entire time, so you slide in the replacement, redundancy is restored, and nobody is aware anything out of the ordinary has happened at all. 😀 The same goes for disks and fans.

Yep. Back then I was managing a few servers in higher ed. (I think late 1990's to early 2000's) Dell was the vendor I bought servers from. I ran Novell on our file/print server 😀 Anyway ... when the PSU failed on one of those servers I immediately called Dell and they sent another PSU the next morning. Meanwhile ... I crossed campus and borrowed a PSU from a colleague. After that I believe I was able to convert those Dell servers to redundant hot swappable PSU's. I had plenty of redundancy with the RAID configuration, etc. ...but I didn't factor in power redundancy. A big mistake on my part. But I was young and it was my first networking gig. We migrated from token ring to ethernet during my tenure there. Man that seems so long ago 😀

SirNickity wrote:

Regarding 20-pin ATX connectors, it's not always a big deal. Many ATX supplies have a 20+4 connector. If you have a 24-pin motherboard, the connector slides on as one piece. If you have a 20-pin motherboard, the 4-pin extension clips on to the end of the 20-pin connector and can be easily removed. Failing that -- if it's one single 24-pin connector -- you may be able to use it anyway. The first 20 pins are the same, and can be connected to a 20-pin socket as long as there's nothing interfering (caps, inductors, etc.) on the +4 end. Failing THAT, you can get a 24-to-20 adapter or just a 20-pin extension cable (which, again, just fits onto the first 20 pins.)

This is good to know. Thank you!

SirNickity wrote:

I would agree the supply in question doesn't appear to be the highest quality supply ever, but it's probably ... alright ... enough. It needs a complete re-cap. Any supply old enough to have a stout 5V rail probably does, but yours especially if it has already lost a few caps. Whether you trust its build quality after restoration is a personal choice. You'll never know when it's going to fail, or how controlled that failure will be, until it fails... so there's always some degree of risk. I once spent a handsome sum for a cream-of-the-crop PC Power & Cooling supply, which failed less than a year after purchase. Meanwhile, I have a couple cheap OEM AT supplies that STILL work. It's a total crapshoot.

I'm leaning towards trying to find a used PSU. But I haven't decided yet. I don't think I'll recap as I don't trust my soldering and PSU trouble-shooting skills enough ... and I don't want to run a faulty PSU. Thanks for all the info. and help!

Reply 13 of 16, by elod

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gdjacobs wrote:
elod wrote:

We (Romania) are flooded with OEM PSUs for the "hefty" price of about 5 bucks.

This is believable. In my experience, Gutless Wonder PSUs are usually light enough to float on water. The next "upgrade" is usually where they throw in fake components made with steel, lead, or concrete to make it seem more substantial.

OEM as in Fujitsu, Acer, HP, Dell. They are usually Delta or FSP. With warranty and as low as 2 Euro for some of them. 5 was the median price. Runs circles around Startech's questionable stuff 😀

Reply 14 of 16, by gdjacobs

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I'd consider Startech to be on par with FSP. Delta, Liteon, Zippy/Emacs, and Etasys are top flight, of course. If you can find one of those that match your rail requirements, grab it with both hands. Worth it even if a recap is needed.

All hail the Great Capacitor Brand Finder

Reply 15 of 16, by obcbeatle

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Just wanted to thank everyone for their assistance. I ended up buying the suggested Startech PSU ... plugged it into this older ASUS motherboard ... and all seems to be OK. The Startech PSU is very quiet ... compared to the original PSU that came with this board (I remember it used to be loud!). Anyway ... thanks again to all those that replied to this thread. Happy Holidays!

Reply 16 of 16, by PcBytes

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obcbeatle wrote:

Just wanted to thank everyone for their assistance. I ended up buying the suggested Startech PSU ... plugged it into this older ASUS motherboard ... and all seems to be OK. The Startech PSU is very quiet ... compared to the original PSU that came with this board (I remember it used to be loud!). Anyway ... thanks again to all those that replied to this thread. Happy Holidays!

Just a FYI thing, but a quick look at BCN (some people here will know the site) revealed it's also an ATNG PSU, just like the Premier.

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