TELVM wrote on 2026-06-12, 09:21:

Feallan wrote on 2026-06-11, 22:13:

... I would think the worst case scenario is a blown fuse in the PSU ...

Disclaimer - Not for the faint of heart ...

Worst Case Scenario

Why am I looking at video of a P3 setup with no HSF on the CPU, GPU and northbridge? Like, it is almost as if this was built to burn. A lot of the fires here are as a result of no thermal cooling, rather than voltage I would say. Even IF you supplied the right voltage to this setup, it would probably burn. No wonder the fire started at the AGP port.

TELVM wrote on 2026-06-12, 09:21:

Worst Case Scenario

According to the ATX standard, this is perfectly normal behaviour.
It has an incredibly wide operating range for the OVP.

appiah4 wrote on 2026-06-12, 09:43:

Why am I looking at video of a P3 setup with no HSF on the CPU, GPU and northbridge? Like, it is almost as if this was built to burn ...

Because that's not "real combat footage", it was staged.

To illustrate (in a "controlled lab test") what will happen to the system if the PSU's voltage regulation ever goes FUBAR.

Two compilations of genuine chinese fireworks:

https://www.youtube.com/watch?v=Ao0X7aouMB8

https://www.youtube.com/watch?v=Vb9zjxqklJA

A notorious scandal just a few years ago:

Exploding Power Supplies: Gigabyte & Newegg Dumping Unsellable Product

Gigabyte GP-P750GM Review - A Power Supply with an explosive attitude

Wish they wrote how they staged it in the video. It only says "wrong voltage supplied", but wrong voltage could be 12V into the 5 and 3.3V lines, or they could have rigged it to just pass through 230V AC... I don't think we should consider such scenarios. If we go with the other videos you posted, it seems the most common "explosive" part are the switching transformers - which you mentioned as what most likely killed my own Corsair 550W PSU. Never opened it so can't confirm, but I have indeed been lucky, that it died so gracefully. Although I'm not sure how exactly this kind of explosion plays out. When the transformer blows up, is there some sudden voltage spike before it goes to 0? Also "good" PSU design should ensure at least some overvoltage protection, so maybe these kick in then. Not very knowledgeable on the topic.

@shevalier - Wouldn't these 12V caps discharge still be protected by OVP circuits? I would think even 20+ year old PSUs with moderately good design should have some zener diodes at least.

@cyclone3d - I did see many bulged and leaking caps myself, especially in things made in the capacitor plague era. Even bought a cheap used 5V heavy Chieftec PSU, advertised as 100% working, I measured it without load and with some small load (2 HDDs and 2 CD roms I think), it was indeed fine. When I opened it up, it had 2 leaked caps, a lot of Fuhyuu ones + Teapo. Well I ended up buying another one, Delta this time. Also measured fine, with nothing suspicious inside so I ended up using it for my build. It does have CapXon capacitors... But I took the risk, it would take me a lot of time to find proper replacement caps

Feallan wrote on 2026-06-13, 15:48:

But I took the risk, it would take me a lot of time to find proper replacement caps

It's not like *finding* capacitors takes a lot of time, as you can just buy them from Digikey or LCSC. Although it does take some time to read the datasheets and so on to figure out which ones to buy.

shevalier wrote on 2026-06-11, 14:41:

Have you seen the prices for the Pentium 3S at a CUBX with 1 GB of RAM?
It’ll be a shame if some modern Chieftec goes burn and takes everything down with it.

Decent modern PSUs are also available, and something with 120-150W for 3.3V and 5V should be good enough for a P3 build, as apparently not all of them are dumb enough to turn fan off when 12V is lightly loaded. This is a much easier route for someone who is not comfortable with soldering, and I think he meant that.

Btw, why is that motherboard so expensive, what's so special about it when compared to other 440BX boards? 1.4GHz PIII-S CPUs are surprisingly expensive as well, although slower models aren't that bad.

Still, socket A CPUs are more powerful than Tualatins, and ISA boards can be had for a relatively low price as well. Especially if you are fine with non-A KT133.

Feallan wrote on 2026-06-13, 15:48:

@shevalier - Wouldn't these 12V caps discharge still be protected by OVP circuits? I would think even 20+ year old PSUs with moderately good design should have some zener diodes at least.

There are no Zener diodes capable of withstanding a load of more than 300 W per pulse.
It is entirely possible to design such a circuit, but I am not sure it would be economically viable.
This is by no means a typical load for modern power supplies.
If I were a power supply designer, I wouldn’t even consider such a load scenario. Because it’s a daft idea.

Mike_ wrote on 2026-06-13, 17:25:

Btw, why is that motherboard so expensive, what's so special about it when compared to other 440BX boards? 1.4GHz PIII-S CPUs are surprisingly expensive as well, although slower models aren't that bad.

I don’t know.
I’ve got two CUBX-L .
One has been modified to CUBX spec (with a voltage regulator for the north bridge and RAM), the other is factory-standard.
It’s a bit of a piece of rubbish, in my opinion. But retro enthusiasts seem to like it.
In theory, you can reach 1 GB of RAM on a PC133 system. In theory.
That means either 4 PC133 CL2 modules or you'll need to look for FB-DIMMs.

Mike_ wrote on 2026-06-13, 17:25:

Feallan wrote on 2026-06-13, 15:48:

But I took the risk, it would take me a lot of time to find proper replacement caps

It's not like *finding* capacitors takes a lot of time, as you can just buy them from Digikey or LCSC. Although it does take some time to read the datasheets and so on to figure out which ones to buy.

Yeah that's the problem. Desolder 20 caps to read the markings, as the interior is usually cramped, find all the datasheets, go through them, read datasheets for modern replacements, find the exact (or close enough) replacements. I'd do it for the chieftec PSU if I really had to, but fortunately the Delta one looks fine

Feallan wrote on 2026-06-13, 20:28:

Yeah that's the problem. Desolder 20 caps to read the markings, as the interior is usually cramped, find all the datasheets, go through them, read datasheets for modern replacements, find the exact (or close enough) replacements.

Manufacturers of ATX power supply units seem to have a strange penchant for using the wrong types of capacitors.

Back in the day, they used 0.1–0.22 μF*50 V electrolytic capacitors in the frequency correction circuits. And there might be as few as five of them scattered across the entire board.
In more recent times, with SMD assembly, they used X-type ceramic capacitors instead of C0G.
I understand that cost-saving falls on the development department, whilst RMA falls on the warranty department.
The summarise effect is zero, but it looks fundamentally corporate. 🙁

Feallan wrote on 2026-06-13, 15:48:

... it seems the most common "explosive" part are the switching transformers ...

The primary switching transistors:

^ KABOOM KABOOM in a Gigabyte GP-P750GM.

In the GN video they comment that one of these fireworks murdered a GTX 3080. Ouch!

Mike_ wrote on 2026-06-13, 17:25:

... Decent modern PSUs are also available, and something with 120-150W for 3.3V and 5V should be good enough for a P3 build, as apparently not all of them are dumb enough to turn fan off when 12V is lightly loaded ...

Paradoxically, though they never monitor +5V load or´+5V DC-DC FETs temp to spin up the fan, most budget modern DC-DC PSUs "idle" the fan at a relatively high speed (usually 800+ rpm).

They do so because, to keep price low, they're typically stuffed with bottom-of-the-barrel crapacitors (ChengX, Jun Fu, etc.), whose only chance to survive more or less "within specs" (at least until warranty expires) is overkill cooling.

From TechPowerUp - CX450M review:

^ Fan control only spins it up when +12V load increases. Fan control couldn't care less about high +5V load, high +3.3V load, or combined minor rail high loads, it just keeps the fan "idling" under such conditions.

But the "idling" speed is relatively high (~950 RPM in this PSU), and that's miles better for DC-DC FETs cooling than a stopped fan.

* BTW the CX450M ain't so bad in the cap department: Elites, Teapos, and one undersized Chemi-Con KMR bulk cap.

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shevalier wrote on 2026-06-13, 18:34:

I don’t know. I’ve got two CUBX-L . One has been modified to CUBX spec (with a voltage regulator for the north bridge and RAM), […]
Show full quote

Mike_ wrote on 2026-06-13, 17:25:

Btw, why is that motherboard so expensive, what's so special about it when compared to other 440BX boards? 1.4GHz PIII-S CPUs are surprisingly expensive as well, although slower models aren't that bad.

I don’t know.
I’ve got two CUBX-L .
One has been modified to CUBX spec (with a voltage regulator for the north bridge and RAM), the other is factory-standard.
It’s a bit of a piece of rubbish, in my opinion. But retro enthusiasts seem to like it.
In theory, you can reach 1 GB of RAM on a PC133 system. In theory.
That means either 4 PC133 CL2 modules or you'll need to look for FB-DIMMs.

You can get 1.5GB of memory with most KT133/KT133A boards as well, most of them seem to support 512MB DIMMs...

alright can I get any guides on what modern, or just any good power supplies I can get for a slot 2 motherboard? ATX ones btw, I mostly need a guide on what amperes I need and what models are reliable for these beasts. but fear not, I will not build a super heavily loaded setup with hundreds of scsi drives, just dual cpus and maybe couple of HDDs

Just discovered this at TechPowerUp's forum and thought it might be of interest to some Vogoners. Good free info on PSUs:

The Power Supply Book by jonnyGURU

.

Bonus track - Oklahoma Wolf still practising "death of a gutless wonder" sports on Youtube 😀 :

PSU Boogaloo - Testing a Lead Power LP-650 ATX Power Supply

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TELVM wrote on 2026-06-29, 10:16:

PSU Boogaloo - Testing a Lead Power LP-650 ATX Power Supply
.

Even if we disregard the fact that the primary-side capacitors are rated for 250 watts.

Since 2001, the sale of power supplies with a power rating exceeding 75 watts that do not feature a any type of power factor corrector (PFC) has been banned in the EU.
Since 2014, the sale of power supply units rated at over 75 watts without active PFC has been prohibited in the EU.

Where did the author of this video find this marvellous work of art?

... Since 2001, the sale of power supplies with a power rating exceeding 75 watts that do not feature a any type of power factor corrector (PFC) has been banned in the EU.
Since 2014, the sale of power supply units rated at over 75 watts without active PFC has been prohibited in the EU.

Where did the author of this video find this marvellous work of art?

Hard to erradicate, this pest. They're very cheap, and uninformed consumers fall for it.

Similar piece of junk caught in the wild in Spain:

^ No trace of passive or active PFC. "13007" BJTs that typically explode above ~250W (so much for the "480W" rating 😀 ). No PI coils on the secondary filtering. Undersized main transformer. ChengX & Jun Fu crapacitors all around. Etc. etc.

.

TELVM wrote on 2026-06-30, 09:02:

Hard to erradicate, this pest. They're very cheap, and uninformed consumers fall for it. […]
Show full quote

... Since 2001, the sale of power supplies with a power rating exceeding 75 watts that do not feature a any type of power factor corrector (PFC) has been banned in the EU.
Since 2014, the sale of power supply units rated at over 75 watts without active PFC has been prohibited in the EU.

Where did the author of this video find this marvellous work of art?

Hard to erradicate, this pest. They're very cheap, and uninformed consumers fall for it.

Similar piece of junk caught in the wild in Spain:

^ No trace of passive or active PFC. "13007" BJTs that typically explode above ~250W (so much for the "480W" rating 😀 ). No PI coils on the secondary filtering. Undersized main transformer. ChengX & Jun Fu crapacitors all around. Etc. etc.

.

Hi,

I also find it funny that it has "Ultra silent power supply" written on it, of course it is silent, they have forgot to install a fan to keep those small aluminium heat-sinks cooled 😁 (But with the issues you already mentioned that is not the biggest problem of this PSU 😀)

MagefromAntares wrote on 2026-06-30, 09:10:

... they have forgot to install a fan to keep those small aluminium heat-sinks cooled 😁 ...

But they did! The cheapest "Hong Kong Phooey special" 120mm they could find:

The "silent operation" comes from the fact that there is no fan control at all, the thing spins @ full swing ~2000 rpm from start to finish ( = as loud as a freight train! 😀 ).

(Hey, at least they placed a raised wire grille above it. That's about the only decent item in the package).

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TELVM wrote on 2026-06-30, 09:46:

But they did! The cheapest "Hong Kong Phooey special" 120mm they could find: […]
Show full quote

MagefromAntares wrote on 2026-06-30, 09:10:

... they have forgot to install a fan to keep those small aluminium heat-sinks cooled 😁 ...

But they did! The cheapest "Hong Kong Phooey special" 120mm they could find:

The "silent operation" comes from the fact that there is no fan control at all, the thing spins @ full swing ~2000 rpm from start to finish ( = as loud as a freight train! 😀 ).

(Hey, at least they placed a raised wire grille above it. That's about the only decent item in the package).

.

Oops, somehow it didn't got to me that they might have a simple fan with two wires connected to the PCB, now I see where it is attached to the PCB on the previous picture(Somehow I expected a fan with at least 3 wires to be connected, but my expectations was too high for this e-waste PSU 😁), well at least there will be a fan spreading the smoke and sparks when it fails 😁

I’ve got no objection to the fact that power supplies with a capacity of up to 200 watts are needed.
Intel’s N100 (or J1800) only draws 25 watts.
I use a J3455M with a Hipro HP-A2007F3 myself.
Nowadays, power supplies like this are usually labelled ‘around 400 watts’.
But 650 watts is the level you’d get with a Ryzen processor and an entry-level RX/RTX graphics card.
And with a power supply like that, the whole thing will just blow up in an instant.

I know I'm late to the party (was busy with other PC projects), but here's my two cents from limited experience with two heavy loaded 462 boards I have.
For one, with an Athlon 1.4ghz thunderbird (the top dog) + a 9250 PCI GPU, I initially got a new chinesium unit from a local store, 50€. I think I ran it for a few months without instabilities, but software readings of sensors reported the 5v line dropping at 4.60v during load, thus outside ATX specs.
After that I got two enermax PSUs off ebay: one EG495EX-VE(W) 485W for 30€ picked up locally, and one EG701AX-VE 600W 50€ from the UK, both with high voltages on 3.3v and 5v rail (30+ A). And, despite that, the Athlon 1.4 system was able to drop the 5v rail to 4.88v during load, sometimes reading as low as 4.80v. Still no instabilities in the system. Counting all the money I spent on those PSUs, I could've got myself one of those legendary Abit 462 boards with P4 12V connector...

And that's what I ended up doing with the second 462 system: An Abit NF7-S2G picked up locally for 50/60€, basically brand new and with less than one year of running. Put in it a Barton 2600+, an FX5600 and a (used) modern Corsair RM650x from a reputable seller. The fan spins only at boot, since the system is so underloaded for such PSU that it woun't spin up even during gaming, thus not helping in venting air out (nothing a rear fan can't fix).
But the good thing? All the rails mantain the ratings no matter what: 5v stays at 5v.

Another thing I wanna point out is that software readings of voltages tend to be inaccurate. I'm currently working on a spare 754 board and, with a good PSU (Corsair RM850X) that keeps it's ratings no problems on a 4790k+1070ti build, in AIDA and Everest it will show the 5v rail at 5.5v, and the 12v rail at 15v(!!!). If those readings were even remotely true, the whole system would've been fried. In BIOS, instead, voltages are rock solid at the ratings.

momaka wrote on 2026-04-25, 22:39:

That said, my GO-TO PSUs for testing 5V-heavy PCs are the Dell/HiPro/Chicony HP-P2507F3P and HP-P2507FWP - these are so over-built that even with a failed cap or two, they still stay in spec most of the time. It was something that JohnnyGuru tested a-way-while back in a "basement" PSU roundup. The old HiPro had a failed cap on the output and still managed to deliver full output power completely in spec. You just don't see this kind of over-building of PSUs anymore, where everything is running right on the limit and well-calculated to last just past the warranty.

Ok, I went on ebay to look for these units and, trying to avoid those with proprietary connectors, I was able to find some... And it doesn't look like they all are that special.
Dell's ones have max output for 3.3+5v at 150W, with 18A and 22A respectively, doesn't feel enough for heavily loaded 5v systems.
The HiPro units seems more interesting, with 175W combined and 25A-18A on 5v and 3,3v.
One thing missing from them is a top fan, so they won't be that helpfull if you wanna build a system in one of those old gray cases.

Mondodimotori wrote on 2026-06-30, 13:22:

... got a new chinesium unit from a local store, 50€. I think I ran it for a few months without instabilities, but software readings of sensors reported the 5v line dropping at 4.60v during load, thus outside ATX specs ...

... two enermax PSUs off ebay: one EG495EX-VE(W) 485W for 30€ picked up locally, and one EG701AX-VE 600W 50€ from the UK, both with high wattagess on 3.3v and 5v rail (30+ A). And, despite that, the Athlon 1.4 system was able to drop the 5v rail to 4.88v during load, sometimes reading as low as 4.80v ...

^ Group-regulated modern(ish) PSUs, designed for "+12V heavy / minor rails weak" systems in the post-P4 era.

Under opposite "+5V heavy / +12V weak" demands, the group-regulated topology can't keep voltages within ATX spec (+5V plummets down, +12V skyrockets upwards).

In this review of a ~2019 Corsair VS650, also group-regulated ...

... look at the Crossload Test 1 ("+12V weak, +5V heavy" draw):

^ Both +12V & +5V voltages are FUBAR.

.

Group-regulated Corsair VS450 defeated by Socket-A system in a Phil's Computer Lab video:

Can your PSU handle Athlon or Duron Socket A processors?

^ If he had used a multimeter we'd see +5V voltage dropping down as he inserts components of progressively higher +5V draw.

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Mondodimotori wrote on 2026-06-30, 13:22:

... modern Corsair RM650x ... ... All the rails mantain the ratings no matter what: 5v stays at 5v ...

^ That's why modern PSUs with DC-DC regulated minor rails are better suited for retro-PCs than group-regulated ones, voltages are rock-steady regardless of cross-loading.

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However, beware of this ...

Mondodimotori wrote on 2026-06-30, 13:22:

... The fan spins only at boot, since the system is so underloaded for such PSU that it woun't spin up even during gaming ...

^ That's not good at all. The +5V DC-DC FETs lack heatsinks, and with the fan stopped, and no air cooling, they may overheat and die, see here.