This is the 375W PSU for that board, with the correct 24 + 6 pin connectors - Compaq EWP105 (Ref Nos. AA20890 / 128399-001 / 120892-001) - and is readily available online. Also, note that it's slightly bigger than a standard ATX supply.

From the 199 page maint. manual and some research: the PSU is model 120892-001 or spare part # 128399-001.
Both are somewhat standard ATX except for supplying a -5v and a 3.3VSB which many newer ATX do not supply.
12V 10A, 5V 30A, 3.3V 36A, -5V 0.15A, -12V 0.15A, 5VSB 1.7A, 3.3VSB 2.0A
Also the 6 pin appears same as a 4pin cpu, can be verified by looking at the traces on bottom of mobo at the 6pin connector.
Here is a replacement supply: http://poweradapter.co/compaq-aa20890-ewp105- … nal-p-5268.html
and another https://www.cbo-do.de/Computer-Cases-Power-su … tml?language=en

🤣 PC Hoarder ! You beat me by one minute
Another thing: the board will not boot with a single processor unless the "terminator card" is inserted into the second cpu slot. The second cpu requires an add-on VRM module.

Thanks for the answers, I've checked the power supplies but I'll try and see if I can make an atx power supply that works with this. I have the CPU terminator card but not the VRM, I assume I don't need the VRM if I only intend to run one CPU. I've attached a picture of it, I don't suppose it's possible to have the wrong terminator.

@Mizar, that looks exactly like the terminator card they normally shipped with, usually branded AMP on the front, and no you don't need the additional VRM unless you add the 2nd CPU. Coincidentally, I'll be picking up a full AP550 Workstation from an e-Waste contact in the New Year.

Nice, I hope you won't have any problems with your workstation PC Hoarder, I've checked the voltages you listed and out of the 6 ATX PSUs I've had lying around outside computers none of them had all the voltages. The closest had everything except 3.3VSB, this is annoying. Thanks again for everything!

Bit more info from online searches -

- the 24 pin atx connector is definitely custom although as there doesn't seem to be a pinout anywhere it's difficult to say just how custom. Some standard pins seem to have been moved and some pins are simply non-standard, plus the wiring colours on the EWP105 don't all conform either.

- the 6 pin aux connector may be supplying additional 3.3V / sense & ground lines and is wired front: black black black and rear: orange (sense?) brown brown, but apparently the board is quite happy to boot without having it plugged in.

Yes, i have this system still in good operation and yes, the power supply is custom, not follow atx spec AFAIK

this is the picture of the power connector
24 pin

6 pin

molex connector for reference

If you want, i can tried to fired up the computer tomorrow with the voltmeter

If you can and it's not too much of a bother, I'd greatly appreciate it!

It's not custom, it's just not ATX.
If I'm not mistaken that PSU and Mobo are to the WTX Standard.
Note that it has both 5v and 3.3v vsb rails.
There are maybe a dozen other non-ATX PSU/Mobo Standards you won't see outside of industrial equipment.

[Withdrawn 460w Suggestion]
I finally found readable labels.
Stay with the 375w. The 460w model only has 15a @5v to the 375w's 29a.

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sorry, English is not my mother language so sometime i'm using some weird term 😁

anyway, this is the result of using the probe.

with the following orientation:

and for 6 pin connector

link to the spreadsheet https://docs.google.com/spreadsheets/d/1AU8e1 … dit?usp=sharing

Wow, thanks a lot for doing it! That must have taken quite a while to do, I will try to see if I can get a normal power supply to boot somehow. Thanks again, you're awesome!

EDIT: How did you power on the PSU for testing? This PSU doesn't seem to have the PS ON green lead that ATX power supplies have.

My machine still in working order, so i simply power it up and measure the voltage directly from the back of connector.
(This PSU should have PS_ON, i suspect that the mainboard must pull that pin to HIGH to power on, maybe pin 13)

Today i got another compaq ap550 and while cleaning the PSU, i also take note of the wire,
so the PS_ON signal is the white one, and it need to trigger high to power on, to power up the PSU, connect it to the 3.3vsb (purple color) .

nhattu1986 wrote on 2020-08-31, 18:30:

Today i got another compaq ap550 and while cleaning the PSU, i also take note of the wire,
so the PS_ON signal is the white one, and it need to trigger high to power on, to power up the PSU, connect it to the 3.3vsb (purple color) .

Hello.
You have correctly identified the connector. It only remains to add that pin 6 is ground. It rings and is soldered on the board along with the black wires.
I have such a power supply unit and a motherboard. The motherboard does not start.
I can't figure out what's missing ...

Found a possible reason why the motherboard does not start. There are no SMD resistors and capacitors on the back of the motherboard.
I need resistor values: R9, R15, R16, R710.
I would be grateful for your help.

Hey Fine People,
I just got that bare board and I have the original PSU, however I do not have the Power button and LED. Anyone would care to send the pinout for the Switches and LEDs? Also the FAN connectors are weird and won't accept a standard 3 or 4pin Fan (seems Ground is missing if using a standard one)

StEeLz wrote on 2021-03-23, 23:40:

Hey Fine People,
I just got that bare board and I have the original PSU, however I do not have the Power button and LED. Anyone would care to send the pinout for the Switches and LEDs? Also the FAN connectors are weird and won't accept a standard 3 or 4pin Fan (seems Ground is missing if using a standard one)

It's a fairly standard front panel harness for this motherboard (SW400) in my Compaq AP550

as is the pinout which (from left to right) is -

1 & 2 - Unused (possibly RESET, but the AP550 doesn't have one)
3 & 4 - White / White (Power Switch)
5 & 6 - Black / Red (Power LED)
7 & 9 - White / Green (HDD LED)
8 - KEY (No pin - Unused)

The fan headers (4-position / 3-pin) are non-standard, designed for these fans which are +12VDC on the two outer pins & GND on the centre pin

You can also just make your own adapter cable for standard 3 or 4 pin fans which follow their +12VDC / GND / +12VDC pinout (ignoring any other sense / tach or PWM wires), which is what I did for the front fan on my AP550

StEeLz wrote on 2021-03-23, 23:40:

Hey Fine People,
I just got that bare board and I have the original PSU, however I do not have the Power button and LED. Anyone would care to send the pinout for the Switches and LEDs? Also the FAN connectors are weird and won't accept a standard 3 or 4pin Fan (seems Ground is missing if using a standard one)

Can you help me with my problem ?? Post above.