Does the system actually turn on? Are you getting video output?

Maybe stupid question, but is th PSU turning on?

Edit:ok it obviously is.

Well, assuming that the hard drive spindle and the GPU fan both stay spinning, then the PSU must be up, so probably not a short and shutdown (my first guess). I seem to remember that motherboard fan header pinouts weren't always standard about power and tach outputs, might be worth trying to check what the motherboard pinout is, and if it matches the connectors on your fans.

[looks like the pinout (looking at the power fan, but they're all the same, just rotated) should be black - red - yellow ]

[On Cyclone3d's point, the manual does mention that the board turns off the fans when in sleep mode, so maybe the motherboard isn't starting up]

[last edit... I found a nice picture on an Arduino message board (https://forum.arduino.cc/t/3-pin-pc-fan/607356 ) that demonstrate the confusion quite nicely. The picture shows one order of the wires and the table just beneath it has a differenet order]

snufkin wrote on 2021-05-28, 15:50:

Well, assuming that the hard drive spindle and the GPU fan both stay spinning, then the PSU must be up, so probably not a short […]
Show full quote

Well, assuming that the hard drive spindle and the GPU fan both stay spinning, then the PSU must be up, so probably not a short and shutdown (my first guess). I seem to remember that motherboard fan header pinouts weren't always standard about power and tach outputs, might be worth trying to check what the motherboard pinout is, and if it matches the connectors on your fans.

[looks like the pinout (looking at the power fan, but they're all the same, just rotated) should be black - red - yellow ]

[On Cyclone3d's point, the manual does mention that the board turns off the fans when in sleep mode, so maybe the motherboard isn't starting up]

[last edit... I found a nice picture on an Arduino message board (https://forum.arduino.cc/t/3-pin-pc-fan/607356 ) that demonstrate the confusion quite nicely. The picture shows one order of the wires and the table just beneath it has a differenet order]

Pinouts all look the same to me, pin 3 just has a different name

debs3759 wrote on 2021-05-28, 16:19:

Pinouts all look the same to me, pin 3 just has a different name

The tables are the same, but the picture/diagram shows the tach pin in the middle on pin 2, rather than +5/+12 power. If the fans that Paatudos has tried all have the tach pin in the middle (and I've seen fans with that pinout), then they won't work because the motherboard has the power pin in the middle. I'm [not] saying this is the problem, just that I think it's worth checking.

[edit, missed a word]

snufkin wrote on 2021-05-28, 16:24:

debs3759 wrote on 2021-05-28, 16:19:

Pinouts all look the same to me, pin 3 just has a different name

The tables are the same, but the picture/diagram shows the tach pin in the middle on pin 2, rather than +5/+12 power. If the fans that Paatudos has tried all have the tach pin in the middle (and I've seen fans with that pinout), then they won't work because the motherboard has the power pin in the middle. I'm [not] saying this is the problem, just that I think it's worth checking.

[edit, missed a word]

the photo of the 3 pin connector is just crud.
annoyingly it's also the first on a google search.
consider it is just wired by some random colorblind chinese guy.
you assume the yellow one is tach, while they just used the yellow one as 12v power, which kinda fits with yellow on pc power being 12v. though yeah then there's red being used as tach.

meh.

adding to the confusion... https://landing.coolermaster.com/faq/3-pin-an … -wire-diagrams/ 🤣

weedeewee wrote on 2021-05-28, 16:32:

adding to the confusion... https://landing.coolermaster.com/faq/3-pin-an … -wire-diagrams/ 🤣

Gotta love the all black wiring. Very stylish. Hotblack Desiato would approve.

DouglasAdams wrote:

“Every time you try to operate one of these weird black controls that are labelled in black on a black background, a little black light lights up black to let you know you’ve done it."

I don't think I've ever run across a 3-pin fan that wasn't wired properly. After trying multiple fans, I would suspect that there is something wrong with the motherboard.

Do these fans work with a 3-pin to molex adapter?

We still don't have an answer whether or not the system is actually POSTing so we can't yet determine if it is just an issue with the fan headers or not.

There's usually a single transistor on those old boards switching all fans on and off. Try to locate it and see wether it works.
Edit: Just looked up a picture. It's most likely this transistor that needs replacing. Check it with a multimeter. You should be able to do so in circuit.

Very insightful, would be cool to know if this was the problem. If so I would personally be too lazy to fix it and just power the fans from some other source. (Given that this malfunctioning transistor does not have any more negative effects.)

(Because I use a modern psu I got myself a fan controller powered by a SATA cable.)

Depending what you know about the history of the board, this damage could have been caused by a single bad fan. Sometimes they draw too much current when they go bad. Even if the board has separate transistors for each header, the failing fan sometimes gets moved around to "test" each header, killing each of them in turn.

Also until about midway through thunderbird athlons or willamette P4s, fan headers could be pretty weak, allowing only 2 or 3oomA before releasing the magic smoke.