More concerning than the 3.3 volt rail being out of spec is the power supply itself - that is a very low end unit, and I would not trust it. I especially wouldn't trust it with a motherboard as rare and difficult to replace as a P5A-B.

There is a review here, it was found to be marginal. And that's when it was new; power supplies often do not age well.

http://ixbtlabs.com/articles2/power/rk-psu11.html

Asus used some crappy sensing chips that seem to fail in this precise way of reading too high voltage, but its also possible to be your supply. Best to validate with multimeter.

I'm thinking it's maybe got no real load on it.

BitWrangler wrote on 2023-07-22, 04:07:

I'm thinking it's maybe got no real load on it.

The ATX standard requires positive voltages to be within +/-5% and negative voltages within +/-10% of specification regardless of load.
If that reading is accurate this PSU is bad.

God, when people will start reading manuals...

shevalier wrote on 2023-07-22, 14:14:

God, when people will start reading manuals...

Thank you, but the jumper was set correct to 3,5 V.

egbertjan wrote on 2023-07-22, 16:25:

Thank you, but the jumper was set correct to 3,5 V.

Then you are completely out of luck.
Asus motherboards with a Vio jumper fully do not use the 3.3V power rail from the power supply.
It is generated directly on the motherboard.
So the board is damaged.

Though flip the board and check for a whisker or something connecting that 4V jumper under.

Does changing the position of those jumpers alter the voltage reading at all?

Use a multimeter. As mentioned above, voltage sensing on those boards is unreliable. A cheap multimeter will be way more accurate.

shevalier wrote on 2023-07-22, 14:14:

God, when people will start reading manuals...

That BIOS screen shows PSU output voltages, it has nothing to do with the mainboard manual.

egbertjan wrote on 2023-07-21, 21:57:

20230720_210928.jpg

That PSU is bottom of the barrel stuff I like to call Schrodinger's Power Supply (will it or will it not let out magic smoke next time I power it on). Others call them "Firecrackers".

Please, get rid of that thing. It was bad when it was new, it's certainly a lot worse 20+ years later... Try looking for a 250-350w ATX PSU out of an OEM machine, you can find them online or at recycling centers for pennies. FSP is my go-to brand for cheap reliable PSUs, Delta Electronics is another good OEM brand, and there are so many more. You can also opt for a modern 300w 80+ PSU if you want to, Super 7 boards are not very picky about 5V rail amperage. I'd still go with a vintage PSU, as new units lack -5v, -12v or both, and some ISA sound cards need those.

Socket3 wrote on 2023-07-22, 18:38:

shevalier wrote on 2023-07-22, 14:14:

God, when people will start reading manuals...

That BIOS screen shows PSU output voltages, it has nothing to do with the mainboard manual.

Yep, especially when the board is connected to an AT power supply

big image
http://hw-museum.cz/data/mb/pic/Asus_P5A-B_F.jpg

shevalier wrote on 2023-07-22, 18:42:

Yep, especially when the board is connected to an AT power supply

OP is using an ATX unit, he even attached a photo to the first post. While the form factor is Baby AT, it has power connections for both AT and ATX power supplies.

LC... I think that's a Deer brand. Their first few models were an attempt to make decent PSU's, but they gave up pretty quickly.

Throw it in e-waste after cutting the power wires from it so nobody's tempted to rescue it.

Seriously, it's that dodgy!

I would definitely not use that PSU. Like others have already mentioned, it was bad even back when it was new. That thing may even be a fire hazard now.
I'd highly recommend you use a PSU that is not that brand and stop using it ASAP unless you really know what you are doing.

P5A-B is a nice board. Would be a shame if the PSU damages it. Or if it damages you or your other belongings.

Socket3 wrote on 2023-07-22, 18:38:

That PSU is bottom of the barrel stuff I like to call Schrodinger's Power Supply (will it or will it not let out magic smoke next time I power it on). Others call them "Firecrackers".

Firestarter.
https://youtu.be/wmin5WkOuPw

Zerthimon wrote on 2023-07-24, 18:05:

Socket3 wrote on 2023-07-22, 18:38:

That PSU is bottom of the barrel stuff I like to call Schrodinger's Power Supply (will it or will it not let out magic smoke next time I power it on). Others call them "Firecrackers".

Firestarter.
https://youtu.be/wmin5WkOuPw

I much prefer this version: https://www.youtube.com/watch?v=CDXNfe2W8c8

I realise this is an old thread, but it came up when i tried to solve a similar problem with my Asus P5A-B. I had the +5V rail showing up as 4.5V in bios power management, producing an error message.
My PSU is a Corsair SF600 with an AT adapter (because i have a power SWITCH on the AT case). Turns out the culprit was one of the motherboard power connectors not being fully pressed in. Stupid error, but these things can drive you nuts if you can't figure it out, and a loose AT connector can easily happen if you have a chaos of cables in the case and you try to organize the chaos with cable straps. Anyway, after pushing it in all the way, the +5v voltage is now back to a safe 4.9V in the bios reading. Cheers!

I would suggest *not* to trust the BIOS voltage readings at all in *any* motherboard, specifically for the PSU voltages (V_core and V_mem, on the other hand, are often accurate or relatively accurate.) Always take a multimeter and verify.

As for the last post above... I find it a bit unlikely that a connector not seated all the way through could have caused such a large voltage drop (0.4V) on the 5V rail. With a current draw of, let's say, 5 Amps (i.e. the board drawing 25 Watts of power from the 5V rail), that's 5 * 0.4 = 2 Watts of heat... dissipate on some tiny pin(s) at best. If this really happened, you'd likely see the connector eventually brown / or even partially melt and the pins' tin coating darken from the heat. If that wasn't the case, then the voltage drop likely wasn't from this (if it even existed at all.) I'm more inclined to think the voltage sensor on the motherboard may be reading the voltages differently depending if the motherboard is warm or cold... and I have personally seen this before on a few of my own boards. But it could also be something else causing this (mis)reading.

Again, just take a multimeter and check when in doubt. I have some motherboards that read the voltages way WAY off... and interestingly enough, very inconsistently off between various PSUs that I have refurbished and tested extensively (so I know they work fine and aren't the culprit.)