While there is the capacitor plague to consider, most electrolytics will fail over time, not always catastrophically on their own but their ESR and capacitance will shift with age as the electrolyte dries out.

Whether this is a problem depends on where the capacitor is used in circuit.

More of an issue IMHO is the absolute state of some of the power supplies sold during the late 90's - early 2000s. Just awful things, poorly designed, made as cheap as possible and barely working at time of sale. I personally saw these cheap power supplies take out motherboards back when they were new, no surprise they are still doing it now.

General rule of thumb for power supplies, if its too light in weight, don't use it. Quality power supplies will be heavier.

BitWrangler wrote on 2022-12-13, 19:35:

Unless you've got a crystal ball you've no idea whether all the lifetime got used up in 24/7 on time for 5 years, or whether they had a "perfect for preservation" life of being turned on every 2 months to present day and ran for only a couple of hours. Yes you can lab experiment a "better caps are better" scenario, but picking up stuff that's been out in the real world and had untrackable use cycles, total crap shoot. The odds are on the side of old caps being bad.

What I'm saying is that with capacitors from the plague era (or known dud series like Chemi-Con KZG) you can almost guarantee they will be dead at this point, while quality caps in even much older equipment will probably be just fine as mentioned by others in this thread. Age and use are not generally deciding factors, but rather the conditions under which those capacitors are working (mainly temperature and ripple). And you definitely CAN estimate how much stress they were under, depending on the location and the purpose.

Bottom line: caps on a 45 year old stereo that has been in constant use since it was bought are probably still fine in most cases, while those in an Antec power supply from 2002 that is still shrink-wrapped are most likely bloated, leaking or just dead.

Hippo486 wrote on 2022-12-13, 20:02:

While there is the capacitor plague to consider, most electrolytics will fail over time, not always catastrophically on their ow […]
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While there is the capacitor plague to consider, most electrolytics will fail over time, not always catastrophically on their own but their ESR and capacitance will shift with age as the electrolyte dries out.

Whether this is a problem depends on where the capacitor is used in circuit.

More of an issue IMHO is the absolute state of some of the power supplies sold during the late 90's - early 2000s. Just awful things, poorly designed, made as cheap as possible and barely working at time of sale. I personally saw these cheap power supplies take out motherboards back when they were new, no surprise they are still doing it now.

General rule of thumb for power supplies, if its too light in weight, don't use it. Quality power supplies will be heavier.

And check where the weight is coming from. Some "clever" bottom-of-the-barrel manufacturers have been known to add sand, concrete, similar or something similarly dense but cheap to add heft to what would otherwise be an ultra-light PSU. Legitimate weight usually comes from metal heatsinks.

_tk wrote on 2022-12-13, 17:04:

To add to this...most of the caps in my vintage audio receivers (40+ years old now) are still perfectly fine and still in spec. Those older quality caps didn't leak or explode...they just went out of spec.

Your ancient gear is all linear A/AB, caps arent being worked hard. Modern gear is full of switching regulators.

_tk wrote on 2022-12-13, 17:04:

Even something as recent as a 486 I have all of the caps both on the mobo and in the power supply are just fine.

mobo sure, power supply not so much, probably on last legs still keeping up with <60W load

dionb wrote on 2022-12-13, 14:08:

Out of interest what PSU was the killer in this case?

It was an old Nspire NSP-300P4B PSU that came with the system. I smelled (and heard) something wrong as soon as it was plugged in.

With how power hungry P4s were, and the fact that there was a bunch of peripherals in this system, I do wonder if the PSU was being overloaded a bit.
There is a 2.4Ghz CPU, Ti4200, Crystal Sound card, Pinnacle capture card, PCI IDE controller, THREE optical drives, zip or LS drive, floppy drive, and 3x 7200RPM IDE drives.

majestyk wrote on 2022-12-13, 08:36:

The southbridge contains the real time clock, ATX start and shutdown circuits ect. so it´s hooked to the 5V standby rail of the PSU.
There are several PSU models that don´t provide sufficient protection against a too high standby voltage in case of a PSU defect. It´s quite possible the faulty standby voltage damaged the southbridge.
The "ground issue" could be due to some burned ground traces on the mainboard. You should inspect both sides very carefully with a good magnifying glass.

I think you are right about the +5VSB causing this, because I smelled (and heard) that something was not right as soon as I plugged it in.

At first I heard the faint buzzing sounds, and I asked my relative if that was normal for that PSU. Seconds later I smelled the bad news.

The relative quickly concluded that I broke it by installing a new CMOS battery (old one was dead after years of faithful service, so I replaced it before hooking the system up).
Quick inspection of the PSU revealed the blown up caps, and I was reluctantly absolved of the fault 😀.

Based on the advice here, I will go over the traces.
I also checked some pins from the ATX connectors against ground on the board, only pins 17-19 show proper ground, all others were open circuit or very high resistance, including pins 3,5,7. Now it's possible that not all are supposed to be used, but I thought it was strange.

What are the chances that the "meltdown" of the south bridge is the main problem here, and that a replacement would fix it? If the problem occurs outside of it (causing the extreme heating up of the chip), it might be harder to pinpoint.

TheMobRules wrote on 2022-12-13, 20:07:

Bottom line: caps on a 45 year old stereo that has been in constant use since it was bought are probably still fine in most cases, while those in an Antec power supply from 2002 that is still shrink-wrapped are most likely bloated, leaking or just dead.

I have a few BNIB Stereo receivers from the late 70's and early 80's. As long as you bring them up slowly (dim bulb tester as a safety helps too) they are fine. They don't need to have been run daily for the past 40 years. Those caps were good quality (at least in good quality units).

I also have a BNIB Antec power supply from ~2003. Took it apart and it noticeably has a few bad caps in it. I did turn it on and it powers on ok and boots an old mobo I don't care about, but I'm sure that PS will go out in spectacular fashion if kept running.

That's my point though...it takes 5 minutes for a seller to inspect and photograph the motherboard and inside of the power supply (maybe 10 minutes if a highly integrated OEM). That will tell me more than what a photo of the post screen will. If the seller is afraid it'll blow, then sell it cheap and/or put on craigslist as-is. I'd take a swing at a $30 P4 Dell but the same cannot be said for a $100+ one on ebay.

_tk wrote on 2022-12-15, 07:55:

That's my point though...it takes 5 minutes for a seller to inspect and photograph the motherboard and inside of the power supply (maybe 10 minutes if a highly integrated OEM). That will tell me more than what a photo of the post screen will.

I've never seen a seller opening the PSU just to take pictures of the inside because it brings it's value down. PSUs are usually secured with a warranty seal that has to be broken to open the PSU. Broken seal = it was already repaired before or it's faulty so someone tried to repair it. It scares potential buyers away. It's especially true with OEMs that need every single piece intact to be valuable so sellers don't like to mess with them at all. Replacing proprietary PSUs is a nightmare anyway so if it works then it works, if it's bad then good luck finding a replacement.

I don't see the value in repairing an i845 based motherboard when i865 based motherboards (which are faster and offer support for higher FSBs and CPUs) are a dime a dozen, unless of course this is something you enjoy for the principle of it. If you're just looking to get a decent Pentium 4 system going, salvage what still works from this system (IMO the Ti 4200 is probably the most valuable asset, it probably costs more than the rest of the components added up nowadays!) and go for a replacement board.

Garrett W wrote on 2022-12-15, 09:35:

I don't see the value in repairing an i845 based motherboard when i865 based motherboards (which are faster and offer support for higher FSBs and CPUs) are a dime a dozen, unless of course this is something you enjoy for the principle of it.

Yep, that's exactly it. However, given the tools required to properly replace a BGA chip, that board is going to become either a piece of decor, or a thing to practice soldering skills on.

Mandrew wrote on 2022-12-15, 09:19:

_tk wrote on 2022-12-15, 07:55:

That's my point though...it takes 5 minutes for a seller to inspect and photograph the motherboard and inside of the power supply (maybe 10 minutes if a highly integrated OEM). That will tell me more than what a photo of the post screen will.

I've never seen a seller opening the PSU just to take pictures of the inside because it brings it's value down. PSUs are usually secured with a warranty seal that has to be broken to open the PSU. Broken seal = it was already repaired before or it's faulty so someone tried to repair it. It scares potential buyers away. It's especially true with OEMs that need every single piece intact to be valuable so sellers don't like to mess with them at all. Replacing proprietary PSUs is a nightmare anyway so if it works then it works, if it's bad then good luck finding a replacement.

The 486 I bought on ebay a while back had internal power supply pics in the auction listing. I was very appreciative of that and one of the reasons why I bought it.

At this point who really cares if a power supply seal is broken on a used PC that's over 10 years old?

_tk wrote on 2022-12-15, 16:29:

At this point who really cares if a power supply seal is broken on a used PC that's over 10 years old?

Fair point although power supplies were never meant to be opened unless there was something wrong with them. Can't speak for others but I always go for the untouched models because a previously opened PSU sends me negative waves.

Some supplies need cleaned out even if they work fine. The problem is the person poking around inside might know what they are doing or might break stuff.