songoffall wrote on 2024-02-23, 13:27:

they might also just squirt their electrolyte from the bottom. Replacing them fixed the issue.

That's how my APC Smart 1000 died. It pissed on the mosfets nearby. By the time I took it apart it dried and I didn't notice, replaced the cap, turned on and blew 4 of the 6 mosfets. Then after cleaning it and replacing those too, checking for shorts it seemed OK. Current limiting with a light bulb it was acting up, but otherwise worked. Without the bulb it blew the mosfets. Some other parts died too, but replacing them just revealed more faulty pars. At the end I gave up on it.

Caps pissing their insides on neighboring components are no joke.

RandomStranger wrote on 2024-02-23, 13:46:

songoffall wrote on 2024-02-23, 13:27:

they might also just squirt their electrolyte from the bottom. Replacing them fixed the issue.

That's how my APC Smart 1000 died. It pissed on the mosfets nearby. By the time I took it apart it dried and I didn't notice, replaced the cap, turned on and blew 4 of the 6 mosfets. Then after cleaning it and replacing those too, checking for shorts it seemed OK. Current limiting with a light bulb it was acting up, but otherwise worked. Without the bulb it blew the mosfets. Some other parts died too, but replacing them just revealed more faulty pars. At the end I gave up on it.

Caps pissing their insides on neighboring components are no joke.

While not too corrosive, it's conductive, and if it forms connections between pins, you will have a lot of shorts. I think taking all details out and washing both them and the PCB with isopropyl alcohol until no residue is left might help.

songoffall wrote on 2024-02-23, 13:27:

This PSU's filter caps had brown flaky residue around them

Do you have a picture by chance?

I've seen this quite frequently: people mistake glue that's usually used on bigger parts (like the filter caps) for electrolyte leakage. That's not to say I haven't also seen caps leak electrolyte from the bottom. But it's just a lot more rare. In most cases, that tan/brown "residue" is glue that the manufacturers use to hold down parts so they stay in place before hitting the solder bath on the assembly line at the factory. The glue also helps keep the product more resilient to vibration and shock during transportation.

That being said, it was common for many electronics manufacturers in the past to use a tan-colored glue for this purpose before switching to proper electronics-grade RTV silicone. Turns out, this tan glue would often become quite a problem over the years. The typical mode of failure is that it turns brown / black with heat, making it very brittle and also slightly conductive. On top of that, it's actually slightly corrosive and has been known to eat away at traces and component leads over time. Unfortunately, many manufacturers weren't aware of this (or possibly knew but didn't care, since it seems to be some kind of really cheap glue.) Worst of all, some manufacturers still continue to use this glue.

I've personally seen it become conductive numerous times, and in a few cases it was the cause of the problem for the device I was repairing. For those of you who still run speakers from the 90's and early 2000's, have a look inside. Just about every manufacturer used this in these products. Computer power supplies were pretty much in the same boat. If you see it, especially on any parts that it has turned brown or black, remove it completely. For PSUs, try to remove as much of it as possible from the primary (line-connected, "HOT") side, since the higher voltages there are more likely to travel through the glue and cause an issue.

songoffall wrote on 2024-02-23, 13:27:

Because I assumed that an old 500W PSU could power an old Athlon XP 2000+ CPU.

Yeah, I ran through the same ordeal early on in my computer days.
I had a 500W CompUSA PSU and thought it would surely be enough to power everything. It was fine with my Athlon XP system for a few years at the time. But then my PC started becoming more and more unstable, to the point where I couldn't reliably boot. Eventually I determined the issue was the PSU after getting into electronics repair. Took it apart one day and found a bunch of bulging capacitors on the secondary side inside. Not only that, but looking at the PSU more closely revealed that it was a united rated for no more than 250-300 Watts and made by PowMax - a company with rather poor reputation for power supplies (the jokes online were that PowMax would have made a great name for a fire crackers brand, given how most ended up dying.)

That being, even new 500W+ PSUs might not be any better. It all depends on the brand / manufacturer of the PSU. A few years ago, I picked up a KDMPower MIPC MI-X8775CD that had an obviously bogus rating of 775 Watts. Of course, its purchase was on purpose - to see how terrible such a PSU would be, since I like messing / reworking electronics. It was a broken unit off of eBay pretty much being sold for free ($1). Anyways, the PSU was everything I expected it to be - a horribly overrated 250-300 Watt PSU, at best... and with cheap knock-off components and no-name capacitors. I repaired it just for fun (the repair info can be found on badcaps.net if anyone like to see this repair.) I still haven't put it in a system and don't know if or when I will. However, I did load-test it just to see how it would perform... and turns out, not much has change between crappy PSUs' from the late 90's / early 2000's and modern no-name crap PSUs. In many cases, even the design is still based on the same old half-bridge topology - something that's been around since the 80's!

songoffall wrote on 2024-02-23, 13:27:

3. If you see transparent plastic capacitors in your PSU, usually branded RIFA, especially if they are cracking, you might want to replace them. Unless you're a fan of the smell. These are power filter caps, and back in the day people didn't realize they didn't perform well in AC circuits and would often fail. And their failure mode was exploding, releasing magic smoke and a wonderful scent that will stay with you for days.

Yes, RIFA capacitors are notorious for releasing a ton of magic smoke.

It's not that they didn't perform well in AC circuits, but rather the fact that their plastic casing didn't age well with time and would often crack, allowing moisture ingress. This would then lead to lots of excess conduction of current between the foil layers on opposite sides to the point where the cap would overheat / set itself ablaze, and release a ton of smoke in the process.

Equipment with RIFA X2 EMI/RFI caps is pretty old, though - AT and early ATX era. I don't think much equipment had it past the mid 2000's.

songoffall wrote on 2024-02-23, 13:27:

Something that makes me more optimistic about this PSU: it runs a lot cooler, the old one exhausted noticeably warm air, while this one is just room temperature. The heatsinks on this one are far worse though. But it is what it is, I guess.

The fact that the newer PSU exhausts cooler air could mean two things: either it really is more efficient and thus isn't running as hot OR components are running really hot, but those tiny heatsinks are doing a terrible job of removing the heat from them, so the moving air through the PSU doesn't get warm. 😁
Well, pictures are the best way to tell anything about a PC PSU. 😉

momaka wrote on 2024-03-02, 14:08:

songoffall wrote on 2024-02-23, 13:27:

This PSU's filter caps had brown flaky residue around them

Do you have a picture by chance?

I've seen this quite frequently: people mistake glue that's usually used on bigger parts (like the filter caps) for electrolyte leakage. That's not to say I haven't also seen caps leak electrolyte from the bottom. But it's just a lot more rare. In most cases, that tan/brown "residue" is glue that the manufacturers use to hold down parts so they stay in place before hitting the solder bath on the assembly line at the factory. The glue also helps keep the product more resilient to vibration and shock during transportation.

Sadly no pictures, but I know what you're talking about. The glue is hard and plasticky; it's usually on top and under the caps, and the residue is thin and flaky. I found a very similar case on Reddit, so posting their photo here:

I've also tasted the thing, it tasted nothing like glue. I know it's not a good idea to taste crap on a circuit board 😁

momaka wrote on 2024-03-02, 14:08:

That being said, it was common for many electronics manufacturers in the past to use a tan-colored glue for this purpose before […]
Show full quote

That being said, it was common for many electronics manufacturers in the past to use a tan-colored glue for this purpose before switching to proper electronics-grade RTV silicone. Turns out, this tan glue would often become quite a problem over the years. The typical mode of failure is that it turns brown / black with heat, making it very brittle and also slightly conductive. On top of that, it's actually slightly corrosive and has been known to eat away at traces and component leads over time. Unfortunately, many manufacturers weren't aware of this (or possibly knew but didn't care, since it seems to be some kind of really cheap glue.) Worst of all, some manufacturers still continue to use this glue.

I've personally seen it become conductive numerous times, and in a few cases it was the cause of the problem for the device I was repairing. For those of you who still run speakers from the 90's and early 2000's, have a look inside. Just about every manufacturer used this in these products. Computer power supplies were pretty much in the same boat. If you see it, especially on any parts that it has turned brown or black, remove it completely. For PSUs, try to remove as much of it as possible from the primary (line-connected, "HOT") side, since the higher voltages there are more likely to travel through the glue and cause an issue.

songoffall wrote on 2024-02-23, 13:27:

Because I assumed that an old 500W PSU could power an old Athlon XP 2000+ CPU.

Yeah, I ran through the same ordeal early on in my computer days.
I had a 500W CompUSA PSU and thought it would surely be enough to power everything. It was fine with my Athlon XP system for a few years at the time. But then my PC started becoming more and more unstable, to the point where I couldn't reliably boot. Eventually I determined the issue was the PSU after getting into electronics repair. Took it apart one day and found a bunch of bulging capacitors on the secondary side inside. Not only that, but looking at the PSU more closely revealed that it was a united rated for no more than 250-300 Watts and made by PowMax - a company with rather poor reputation for power supplies (the jokes online were that PowMax would have made a great name for a fire crackers brand, given how most ended up dying.)

That being, even new 500W+ PSUs might not be any better. It all depends on the brand / manufacturer of the PSU. A few years ago, I picked up a KDMPower MIPC MI-X8775CD that had an obviously bogus rating of 775 Watts. Of course, its purchase was on purpose - to see how terrible such a PSU would be, since I like messing / reworking electronics. It was a broken unit off of eBay pretty much being sold for free ($1). Anyways, the PSU was everything I expected it to be - a horribly overrated 250-300 Watt PSU, at best... and with cheap knock-off components and no-name capacitors. I repaired it just for fun (the repair info can be found on badcaps.net if anyone like to see this repair.) I still haven't put it in a system and don't know if or when I will. However, I did load-test it just to see how it would perform... and turns out, not much has change between crappy PSUs' from the late 90's / early 2000's and modern no-name crap PSUs. In many cases, even the design is still based on the same old half-bridge topology - something that's been around since the 80's!

songoffall wrote on 2024-02-23, 13:27:

3. If you see transparent plastic capacitors in your PSU, usually branded RIFA, especially if they are cracking, you might want to replace them. Unless you're a fan of the smell. These are power filter caps, and back in the day people didn't realize they didn't perform well in AC circuits and would often fail. And their failure mode was exploding, releasing magic smoke and a wonderful scent that will stay with you for days.

Yes, RIFA capacitors are notorious for releasing a ton of magic smoke.

It's not that they didn't perform well in AC circuits, but rather the fact that their plastic casing didn't age well with time and would often crack, allowing moisture ingress. This would then lead to lots of excess conduction of current between the foil layers on opposite sides to the point where the cap would overheat / set itself ablaze, and release a ton of smoke in the process.

Equipment with RIFA X2 EMI/RFI caps is pretty old, though - AT and early ATX era. I don't think much equipment had it past the mid 2000's.

Here's a video going in depth into RIFA and how they fail:
https://www.youtube.com/watch?v=TB5FL3vziko

momaka wrote on 2024-03-02, 14:08:

songoffall wrote on 2024-02-23, 13:27:

Something that makes me more optimistic about this PSU: it runs a lot cooler, the old one exhausted noticeably warm air, while this one is just room temperature. The heatsinks on this one are far worse though. But it is what it is, I guess.

The fact that the newer PSU exhausts cooler air could mean two things: either it really is more efficient and thus isn't running as hot OR components are running really hot, but those tiny heatsinks are doing a terrible job of removing the heat from them, so the moving air through the PSU doesn't get warm. 😁
Well, pictures are the best way to tell anything about a PC PSU. 😉

I guess I wasn't clear enough; the "new" PSU is actually physically older. The PSU I replaced had a SATA cable, this one doesn't. It's still 24-pin, and has the 4-pin CPU connection, but it's MOLEX-only.

I don't use PSUs post-2005 on retro builds before LGA775 because they almost never have decent power on +3.3v and +5v rails.

Ah OK,
yes that picture from reddit clearly shows what a leaking cap looks like. (And for anyone that cares to know more, those caps are UCC TMV series, which are notorious for doing this. They don't have a vent on the top, so they always leak at the bottom. Luckily, their aqueous-based electrolyte is almost non-corrosive, so they don't do damage to the boards usually.)

songoffall wrote on 2024-03-02, 19:01:

I don't use PSUs post-2005 on retro builds before LGA775 because they almost never have decent power on +3.3v and +5v rails.

Good, that's a relative safe bet.
I personally use whatever on whatever... but I repair/inspect/analyze and bench-test all of my PSUs, so I know what they are capable of and what they aren't. This allows me to know what system I can use them in. I've had very few issues in doing this. The worst one resulted in just random crashes. It was actually with an old PSU (that I recapped) powering an old motherboard. The board just kept crashing randomly. What's interesting is that I received that motherboard and that PSU as a combo in a computer. Then again, maybe that's why they were free. 😁

momaka wrote on 2024-03-03, 09:28:

Ah OK, yes that picture from reddit clearly shows what a leaking cap looks like. (And for anyone that cares to know more, those […]
Show full quote

Ah OK,
yes that picture from reddit clearly shows what a leaking cap looks like. (And for anyone that cares to know more, those caps are UCC TMV series, which are notorious for doing this. They don't have a vent on the top, so they always leak at the bottom. Luckily, their aqueous-based electrolyte is almost non-corrosive, so they don't do damage to the boards usually.)

songoffall wrote on 2024-03-02, 19:01:

I don't use PSUs post-2005 on retro builds before LGA775 because they almost never have decent power on +3.3v and +5v rails.

Good, that's a relative safe bet.
I personally use whatever on whatever... but I repair/inspect/analyze and bench-test all of my PSUs, so I know what they are capable of and what they aren't. This allows me to know what system I can use them in. I've had very few issues in doing this. The worst one resulted in just random crashes. It was actually with an old PSU (that I recapped) powering an old motherboard. The board just kept crashing randomly. What's interesting is that I received that motherboard and that PSU as a combo in a computer. Then again, maybe that's why they were free. 😁

Sadly, I don't have enough space/equipment at this point to bench-test most of my equipment 😁 as long as it passes the smoke test, I'm usually fine. Which is why I open up and visually inspect PSUs and replace the REEFAs and any faulty-looking caps beforehand.