On computer PSUs what wears out other than capacitors

[Hogwild]

Hi everyone:

I have an 8 or 9-year-old Seasonic SS-430HB PSU. I'd like to put it to use, but I'm assuming the caps might go bad soon. If I replaced the caps, would that be enough to keep it going long-term, or are there other components on computer PSUs that die with age? What else, if anything, would I need to replace?

Thanks.

[cdev]

Fan may benefit from a tiny bit of lubrication or possibly bearings wearing might indicate replacement, possibly. It depends on the fan.

[Hogwild]

Thanks. Yeah, I knew about that. True on most moving/mechanical parts. So far, the fan sounds as quiet as it did the day i got it. It's a Yate Loon, so no surprise. Will resistors or any other components need replacing?

[thermistor-guy]

Hi everyone:

I have an 8 or 9-year-old Seasonic SS-430HB PSU. I'd like to put it to use, but I'm assuming the caps might go bad soon. If I replaced the caps, would that be enough to keep it going long-term, or are there other components on computer PSUs that die with age? What else, if anything, would I need to replace?

Thanks.

I'd look carefully at the heatsinking arrangements, and where practical, replace any thermal paste or pads used. They become less effective with age, especially after 8 or 9 years, either
due to slow chemical changes, or due to thermal cycling that loosens the interface layers (loose contact = high thermal resistance).

[cdev]

Inspect them and all other passive components (capacitors, inductors) closely and replace any that show even the slightest sign of cracking or breaking in any way. Similarly for any solder joints, redo any solder joints that look iffy. Since you are in there already.

Specifically with power supplies, sometimes they have footprints for missing components that might be present in better models. Sometimes you might want to figure out what those other components are and add them. More or better capacitors might reduce RFI for example, but make sure you know what you are doing and that it wont cause problems. Especially on the mains voltage side of the supply. Specific laws likely apply to lines powered devices on the line-facing side. Make sure you understand them and comply with them or leave that part of the supply alone.

Thanks. Yeah, I knew about that. True on most moving/mechanical parts. So far, the fan sounds as quiet as it did the day i got it. It's a Yate Loon, so no surprise. Will resistors or any other components need replacing?

[Hogwild]

Thanks. If a resistor is bad, will it be obvious, or not necesarily? I hadn't thought of thermal material. That's a good idea. Where do I buy replacement thermal material? Does it matter what kind?

[amyk]

Seasonic is a pretty good brand so I wouldn't worry about doing any servicing beyond cleaning out the dust and lubricating the fan(s).

[Wan Huang Luo]

Methinks you're a little too cautious. I'd just whack that PSU in and use it with confidence.

[wraper]

Hi everyone:

I have an 8 or 9-year-old Seasonic SS-430HB PSU. I'd like to put it to use, but I'm assuming the caps might go bad soon. If I replaced the caps, would that be enough to keep it going long-term, or are there other components on computer PSUs that die with age? What else, if anything, would I need to replace?

Thanks.

I'd look carefully at the heatsinking arrangements, and where practical, replace any thermal paste or pads used. They become less effective with age, especially after 8 or 9 years, either
due to slow chemical changes, or due to thermal cycling that loosens the interface layers (loose contact = high thermal resistance).

That is some very bad advice. And it would be somewhat valid only if some very bad thermal paste was used. Most likely there are just thermal pads anyway.

[james_s]

Agreed, I have never replaced thermal paste unless I had to take a part out anyway. You are far more likely to damage something trying to replace the paste than by just leaving it alone. Personally I would just blow the dust out of the thing, inspect the fan and look for any bulging or leaky capacitors. If everything looks ok then just use it, the more you mess with it, the more opportunities you have to screw something up. I have seen a LOT of good usable gear ruined by people trying to fix what wasn't broken.

[In Vacuo Veritas]

Methinks you're a little too cautious. I'd just whack that PSU in and use it with confidence.

Good Lord yes! The amount of people getting a legit psychological disorder every time they see a capacitor is incredible. What next? Will they be on Dr Phil?

[GreyWoolfe]

Methinks you're a little too cautious. I'd just whack that PSU in and use it with confidence.

Good Lord yes! The amount of people getting a legit psychological disorder every time they see a capacitor is incredible. What next? Will they be on Dr Phil?

No, Jerry Sprinter.  He loves psychological disorders.

[Wan Huang Luo]

Agreed, I have never replaced thermal paste unless I had to take a part out anyway. You are far more likely to damage something trying to replace the paste than by just leaving it alone. Personally I would just blow the dust out of the thing, inspect the fan and look for any bulging or leaky capacitors. If everything looks ok then just use it, the more you mess with it, the more opportunities you have to screw something up. I have seen a LOT of good usable gear ruined by people trying to fix what wasn't broken.

Fix it till its broken. Trap for young players!

[ogden]

Snubber resistor or it's solder joints may become point of failure.

[Rasz]

dont forget piston return springs

[SoundTech-LG]

Any mechanically attached component that is mounted off-board to heatsinks etc....  such as regulators, transistors, diodes. Check for cracked solder, or broken leads. Maybe big transformers have cracked solder rings too. Check and re-flow. Have fun!

[thermistor-guy]

Agreed, I have never replaced thermal paste unless I had to take a part out anyway. You are far more likely to damage something trying to replace the paste than by just leaving it alone. Personally I would just blow the dust out of the thing, inspect the fan and look for any bulging or leaky capacitors. If everything looks ok then just use it, the more you mess with it, the more opportunities you have to screw something up. I have seen a LOT of good usable gear ruined by people trying to fix what wasn't broken.

It depends on the person attempting the fix. I've never had a problem. But at the far end of the scale, we have folks here refurbishing/repairing 8.5 digit DVMs, which is beyond my current ability.

The OP didn't indicate his/her level of expertise. As a general rule, those who can be discouraged, should be discouraged.

But in answer to the OP's question - what wears out in PSUs over time - yes, the thermal interfaces do degrade.

[james_s]

I generally assume that if someone has to ask, then they probably shouldn't start trying to fix things that aren't broken yet. The people who have the expertise to replace parts with little risk of additional damage don't usually need to ask what parts they should replace. Now this is in no way criticizing people who are inexperienced, everyone has to start somewhere.

[Hogwild]

Okay, I decided to take some photos to see if anyone could spot anything I missed. The item is a bit hard to photograph, what with all the enclosed spaces, but I did my best to light it.

Anyone see anything that doesn't look good?

In the last shot is a piece of plastic with some goop on it. That fell off one of the coils as soon as I touched it. What is that goop, and I assume I should get some and remove old goop and apply a fresh coat?

Thanks

[Hogwild]

Here are a couple more, including the plastic piece that fell off.

[james_s]

The goop is just glue, the plastic piece is an insulating separator to prevent shorts to the metal case. You can stick it back on with a small dab of caulking or similar adhesive.

[Nusa]

If there's nothing wrong and it operates as expected, don't fix it! In the absence of symptoms, the only normal preventative maintenance is blowing out accumulated dust. Use it, or keep it on the shelf as a spare.

[Hogwild]

I blew out all the dust carefully. All caps at least appear to be fine. No burn marks, nothing else stands out. Thanks!

A related question: I have another ATX PSU here, labelled Alpha. This was put in at a store, I believe in 2014.  I can't find any reviews or teardowns of this PSU.

Here are some pics. Can anyone see anything that stands out as bad? It's still working fine. Haven't checked the rail voltages lately, but I thought I would add this to my friend's collection as a backup, just in case.

[Hogwild]

Here are a few more angles of the ALPHA PSU.

[james_s]

Looks like a really cheap one. Phenolic PCB, no-name Chinesium capacitors, and a few of those smaller caps look like they may be bulging at the top but it's hard to tell from the picture. If the capacitors are ok then it's probably ok to use, but it's certainly not a high end one.

[Hogwild]

james:

Thanks. No, no bulging caps, AFAICT. That's just an optical illusion. Sorry, I should've checked my photos more closely before posting.
Do you mean literally no name, as in generic, or you just can't see the brand name. Most of them appear to be CapXon. From a quick glance, these appear to be a poor brand, yes?

Yeah, I am thinking of this as a temporary emergency backup in case his main PSU dies. His main PSU will be the Seasonic in the photos above.

[amyk]

That's not a very cheap one but certainly low-end. The UL number E194545 is no longer registered but a search comes up with http://azsurplus.ca/index.php?main_page=product_info&cPath=2_101&products_id=9006 and https://cdn8.bigcommerce.com/s-a1x7hg2jgk/images/stencil/1280x1280/products/2554/13469/lc-250-w-atx-power-supply-vt-250atx-4.20__51097.1489931696.jpg?c=2?imbypass=on (attached) which points to L&C being the OEM. They don't have a good reputation, because they're usually extremely overrated. It's a 200-250W unit at best.

[coppercone2]

Capacitors degrade and you can change them to increase reliability with ones from digikey

Next on the list IMO would be
1) fuses - they degrade
2) bearings - look at industrial documents to measure bearing integrity. an interesting test might be vibration measurement at high speeds mount it on a shaft where the a fan turns the bearing and hit it with an air compressor it will go really fast and you can measure it. Compare to a new bearing of the same kind.
3) Protection elements that rely on heat : resistance change with temperature
4) MOV's degrade with age and they are basically wear elements that absorb mains variations
5) the X and Y caps connected to mains before the transformer take beatings
6) solder joints where the cable plugs in and the ATX  connector, or the crimps (if its done right)
7) the switch contacts
thermal grease gets crusty and it ages, so do thermal pads. its documented
9) gas discharge tube ages
10) check for screws getting looser from vibration
11) hot things and suspicious plastics like barriers between the PCB and the chassis

you can load it down and measure heat sinks and stuff to see if they age

the switching transistors characteristics may change with age enough to effect operation noticeably. the gate resistor on the switching transistor also may experience heavy transients and you might wanna replace that too. the diode too.

keep in mind the computer is expensive and these replacements are not,

The biggest problem I had with these is that doing maintenance on them is annoying because of the silastic adhesive. It makes me not want to work on them at all. And they also solder the heat sinks down alot which is a pain in the ass unless you have a strong iron just for this job... don't attempt it with your electronics iron IMO. Take it apart and carefully think about what you are doing and cut around the adhesive with a exacto... but I found sometimes you want to remove certain things to get at other things unless you wanna risk ripping stuff out with adhesive still attached. It feels like doing surgery. What can help here with the heavy ground planes and stuff is to melt the solder and actually blow it out with duster or an air compressor when its molten. But you really really need to do a super precise visual inspection after wards to get rid of the solder splattered everywhere.

On older fans in bigger supplies the bearing is often held onto the shaft with a cir-clip and you can bang them out. I think they are standard size. I never bothered but I should have.

[james_s]

I mean the brand name is meaningless, it's just some random Chinese company nobody has heard of, probably one of 20 different brand names they stick on parts coming off the line. Noname == not any reputable name brand.

[Wan Huang Luo]

New capacitors for a $15 ATX power supply? 
Vibration measurement of its fan bearings?? 
New fuses just for fun? 

In the time it takes to just open it and start poking around you could have just bought another $15 PSU shamazon.

[coppercone2]

you learn something about decay in that circuit topology assuming you compare/measure the parts and make less e-waste assuming the shipping packages are not ridiculous whats your point... yea i know typical chinese attitude who gives a shit about the environment or learning about 'reliability' and 'wear' (i know their alien concepts to you given my business with China, you guys just think about cost and making a quick buck.. not sure you even test the designs). Enjoy your smog when someone throws the PCB into a fire pit to try to recover a bit of precious metal or something. Or are you gonna ship it to pollute Africa?

You also learn about the enclosure and how well mounted the fan is and chassis thickness choice etc based on the bearings. Keep laughing but people who do this might end up learning something and being able to build a better product in the future that will last longer and be cheaper (because you know what happens exactly).

[james_s]

I think about value for my limited time. For a $300 power supply? By all means, repair it. For a $15 power supply? Life is too short unless you are broke and absolutely need to get it working. There's an old saying that applies here, "You can't polish a turd."

Also while I've had fuses fail mechanically once or twice, to say they wear out is ridiculous. I have never replaced a fuse as a preventative measure, that's just silly.

[coppercone2]

it depends how they spec it, most people don't bother specing a proper fused based on i2t

you might not get many cycles on it if its done wrong

[Nusa]

it depends how they spec it, most people don't bother specing a proper fused based on i2t

you might not get many cycles on it if its done wrong

Are you seriously suggesting that even above-average consumers are in a position to question the fuse specifications made by whoever designed the circuit?

In any case, the fuses the rest of us are talking about generally get ONE cycle before needing replacement. Thin filament in glass tube usually soldered to the board as a safety measure. If they blow, there's usually a good reason! I'm not sure what you're talking about anymore.

[coppercone2]

the designers don't always do it. People just measure power and ignore inrush because you need a current clamp. I talked to engineers that did not know what i^2t even was.

The equipment works fine but the inrushes cause the fuse to be fragile and break. If you have a current clamp you can. People just say 'its fire protection' but you need to do some serious design work for correctly determining how many times it can cycle before it breaks.

[james_s]

In the ~25 years I've been repairing electronics frequently I think I've seen *two* fuses fail without any apparent fault. One was in an Apple CRT monitor of a particular model which was known to have a slightly under-spec'd fuse that would blow occasionally when the degauss coil kicked in. The other I forget now what it was in, but that is two out of I don't even know how many hundreds or even thousands of devices that have passed through my hands. I have bungled a repair and damaged the thing worse than it was when I started more often than I've seen a fuse fail without there being an obvious fault with the equipment it's in, and that too is quite a rare occurrence. There is absolutely no reason to mess with the fuse unless it blows, and in that case the first thing you should do is look for a fault.

[BravoV]

Dust also will affect the components life. As its accumulated thru time never cleaned, heat dissipation will suffer severely and affecting components life.

Starting from making the fan blow air weaker as dust stick and evenly coated at the fan blades, the heatsinks and various components that heat up.

Also sometimes at high humidity environment, the layer of thick dust at may cause intermittent or weird problem if the dust is damp.

Picture worth thousand words, randomly googled photo ... click to expand the photo.


Mid to top tier PSU nowdays have those feature that deliberately by design turns the fan off, when the PSU is lightly loaded, this in long run actually will make the PSU less dusty and longer life.

[Rasz]

I mean the brand name is meaningless, it's just some random Chinese company nobody has heard of, probably one of 20 different brand names they stick on parts coming off the line. Noname == not any reputable name brand.

L&C is a big oem in PC power supply space, they are quite known (so I wouldnt call them a noname). They are known as a bottom feeder tho ;-)
The only thing this supply is good for is learning about cost optimizations, it is made to survive ~2-3 years before dying at minimal manufacturing cost.

[Hogwild]

Well, thanks everyone. I guess I'll give the Alpha as an emergency, temporary spare, and the Seasonic as something to use first. Thanks for all that info!

[TheNewLab]

if PSU still works just keep it in. what else?
Mechanical..and clean connections. so dust and clean contacts in the machine motherboard, etc

I have an Apple IIC that still works fine.
A PPC9500 I still use with an upgraded daughter card and running Linux.(a previous version of Ubuntu)

And about dis..ing Chinese stuff. remember Back to the Future? and how Japanese were cheap?

most all are internals, and have been for a long time. Apple has been using FoxCon since the 1980's
The cheap stuff are the back yard, extra room, garage built stuff...Even that they are hacking the code from other small players in the west...

What I'd be concerned are the counterfeit Thai, and SE Asian ICs

[james_s]

Plenty of good stuff is made in China already, but so is a lot of garbage. All the low end companies produce stuff there because it's extremely cheap. When I grumble about Chinese crap I'm not saying that everything made there is crap, but most of the crap is made there.

[Hogwild]

I don't know about using caulking to put that piece of plastic back on the inductor. Is there something that works better than that, or do we all agree caulking is fine? Latex?

[james_s]

Caulking works fine, I've used it lots of times for similar applications. Latex or silicone works. Some will warn that silicone shouldn't be used on electronics, indeed it can cause corrosion but in practice I have not found it to be a problem so long as it's not sealed in an airtight enclosure. It only takes a dab.

[coppercone2]

i used the polysilane based silicone on electronics before in a open enclosure and I did not see any signs of corrosion 1 year later. I used it to seal around solder joints as an experiment. I  thought the tin might turn blue.

[Hogwild]

Do I need to clean the old goo/adhesive off the plastic protector sheet and/or the inductor it was on, or can I just put the caulking right on top of it all?

Much appreciated, everyone.

[coppercone2]

Do I need to clean the old goo/adhesive off the plastic protector sheet and/or the inductor it was on, or can I just put the caulking right on top of it all?

Much appreciated, everyone.

if you follow the advice of people fixing bath tubs on youtube, then it will be stronger if you clean it.

[Per Hansson]

With age the glue manufacturers love to use on the PCB usually becomes conductive.
This leads to new paths forming in the PCB and things going kaboom when for example the PFC circuit gets out of whack.
It was extremely common 30 years ago, as it is today, and it was a known issue back then, as it is today.
I'm surprised nobody covered it yet.
You can clearly see how bad it gets with heat in the plastic shield that fell off, that has become completely black...
Your Seasonic PSU does not look that bad otherwise in the glue front, but it's something to keep in mind.
The capacitors are United Chemi-Con KZE and they will last a very long time unless the PSU is severely abused.
(As in a recap would be completely pointless before the PSU is at least 20 years of age).

The other PSU built by L&C can be used to fill up the electronic waste container.
Well, ok, it has input filter etc but everything is severely underrated, the label says 420w, it would never deliver even 50% of that within ATX specifications.