Help me: fanless HP PS 26/36/42A - RC Groups
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Jul 03, 2011, 12:24 PM
Registered User

Help me: fanless HP PS 26/36/42A

i have 3 types of fanless PS here, it is:

ESP128, 280127-001, 305447-001
26 Amp (325W)

DPS-460BB B, 361392-001, 325718-001
36 Amp

3. DPS-525EB A, 389997-001, 384232-001
42 Amp

They all have the same packaging and PCB layout of pins.
All have -12V, 5VSB, 3.3VSB, 7VSB (strange value).

I made a photo of top and bottom of the 26A version, on which i make the tests.
The top pins measure (except the 12V line, which of course does not run yet) when plugged in:

GND - 12V - 6.7V - 2.5V - 0 - 2.5V (short pin) - 5.2V - 3.3V - 12V - GND

Bottom side seems to be all ground.

I measured not yet converted ESP113 and the 3 pins which need to be connected to ground measure 0.35V (remote sense resturn), 4.54V (power on), 0.14V (PS fast shutdown) if image here have correct description:

So, this does not helped me much.

In this case:
- it have many SB outputs, so i think measured 6.7V, 5.2V and 3.3V will be that outputs, right?
- do i seek for 2 or 3 pins which will need to be connected to ground?
- all PS i modified had always the shorter PCB pin connected to ground, what signal is usually that, should i start with this pin?

Thanks for help.

DC side ungrounding look simple - isolating one case screw.
And it have the usual 2 pots inside for setting.
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Jul 03, 2011, 02:03 PM
Registered User
Success so far.
The LED is green, the PS provide +12V and on the pin between the ones which are grounded is now also -12V.
On +12V it provide 12.30V, but i did not tested it yet, because i run out of banana female connectors.

Now on the bottom side, one pin now have about 12.2V.

How to identify voltage control, should it be there?
On top, all pins are identified:
GND - 12V - 6.7(7V) - power control pin - minus 12V - power control pin - 5V - 3.3V - 12V - GND
Jul 04, 2011, 02:02 PM
Registered User
Tested like this with 22A load, so connecting these two pins to ground seems to be enough.
Now i will try to find voltage control pin, there are 7 pins on bottom side, 2 seems not to be connected to anything...
Any hints how to do it?
Based on guide from Xandrios, i will connect 1kOhm resistor to +12V and test each pin one time and watch the output voltage...
Jul 04, 2011, 03:39 PM
Registered User
Okay, it seems i can make this alone.
1kOhm resistor connected to 12V give me 13.52V from basic 12.26V when connected as on image.

I can pull 22A using my iCharger, but at the moment when i stop the charge, the PS shut off.
Does not happen if i draw only 20A.
Is the voltage too high?
Or is it the spike from unloading which go to the voltage control pin?

Also, connecting the resistor to the far right pin from the 5 tinned ones, i get voltage raise to 12.67V.

Other 3 pins seems to have no effect on the voltage, the 2 marked ones on the left seems not to be connected anywhere.

Now what, connecting the pin in the middle to +5VSB or +3.3VSB?
Using smaller resistor (i have 470 Ohm and then 220 Ohm)?

I used this guide:
Jul 13, 2011, 10:43 PM
Registered User
I would like to offer my appreciation for your posts jointer, got me off to a good start!

Still some clean up work to do, I didn’t have the correct color small wires, or a small enough iron tip to do much of a solder job on them, but that will be easy enough to fix.

Started to put power leads on, then decided to just solder 2 sets of bullet housings right to the board. Some shrink wrap for protection and polarity identification, seems to work well. Once I’m happy with it and run more load tests I plan to coat the contacts with the brush on tape.

And I have another if I decide to go 24V. Got a unbeatable deal on them too, and I’m helping my company with it’s recycling efforts. Total investment so far, essentially nothing!

Jul 14, 2011, 06:45 AM
Registered User
I am glad it helped someone.
Which versions you have?
I started with the 26A units, i guess the 36 and 42A units will have the pins the same, but i did not have time yet to try it.
I also need to figure out how to cool them.
I was thinking about putting 80mm fan in the place where you have the can on the photo (making hole in the cover).
But there is another option, 2x 40mm fans at the output PCB, blowing air inside.
Second PS placed reversed on top of first and these 40mm fans in the middle between that two PCB outputs.

They are fanless, because the fans are integrated in the server, not because they do not need coooling - they do.
Jul 14, 2011, 12:50 PM
Registered User
They are the DPS-460BB B, 361392-001, 325718-001, 36 Amp on 12V jobs.

Yes, heat is part of my concern. Haven't decided what to do yet, I've only briefly tried it at ~5 amps, and it did get warm. I'm going to go over to our server room and see if I can take some temps, and get an idea of airflow.

Maybe a couple small fans at the end? I want to maintain the easiest to handle package I can for transportation. I might add on to the end to help protect the board and plugs, pehaps the fans will be part of that.

Jul 26, 2011, 01:27 PM
Registered User
DPS-525EB A (525W/42A) - same wiring.
Without resistor on the voltage control pin, they give 12.59V both (i have 2).
For DC side ungrounding, i need to isolate both case mounting points on the DC side.
After that will be done, i will try to use 2x 40x20mm fans in front for cooling.
Aug 21, 2011, 01:06 PM
Registered User
My dirty solution for cooling 2x 26A units.
I found 2x 40mm fan is not enough when both units are mounted together.

This is not pretty, but noticable better, some air flow inside and the rest cools the top of the PS.

I am working on different solution for 42A units.
Aug 21, 2011, 01:26 PM
Registered User
Originally Posted by jointer
My dirty solution for cooling 2x 26A units.
I found 2x 40mm fan is not enough when both units are mounted together.

This is not pretty, but noticable better, some air flow inside and the rest cools the top of the PS.

I am working on different solution for 42A units.
Why not just use one larger fan? It will be quieter than those 4 screamers.
Aug 21, 2011, 01:59 PM
Registered User
Actually, i bought too quiet version, so i helped myself by connecting them to +5V of the second PS, so that is about 18V on them.
They are now as noisy as common chargers.
Notice the two zip ties.
The fans are glued together and fixed on the grid by that zip ties.
I could not fix a 80mm like that.
Also, i bought these fans hoping i will use only 2 of them and 2 other on the 42A unit.
Now at full load, the PS is warm on the other end (AC side), so the plan for 42A is to have 80mm fan from the top, if you look at photo from Bongo Fury, roughly where he have the can.
This solution would not be enough.
Oct 13, 2011, 09:58 PM
Registered User
I noticed when I set up one of these the heat is mostly at the top. By putting the "tops" of the PSU's face outward your not creating hot air in between them.

Originally Posted by jointer
My dirty solution for cooling 2x 26A units.
I found 2x 40mm fan is not enough when both units are mounted together.

This is not pretty, but noticable better, some air flow inside and the rest cools the top of the PS.

I am working on different solution for 42A units.
Oct 24, 2011, 12:14 PM
Registered User
The final cooling solution for 36A and 42A units.
Only missing protective grid for the fans (must buy some).
The DC side produce much more heat at full load then AC side, so the fan is on the right place.
Also it is the only place where the air could get in, under the fan are some coils and a transformer, the remaining side area is covered by heatsinks, so it is not possible to get air inside on some other place.
Because the 80mm fans are large, the PS is much less noisy then the fast spinning smaller fans in regular actively cooled power supplies.
But this does not look as clean/compact as them.
Jul 09, 2012, 05:38 PM
Registered User
Good work jointer! I just acquired one of these power supplies and plan to make use of it.
Jan 22, 2014, 06:12 AM
Norwegian mc rookie
Hi Jointer! Excellent thread! Excactly what I needed!

I have the same units, two of the 36A psu´s
But, pardon me for asking a possible dumb question here. What are the reasons for soldering the the two tiny pins in the middle to the ground? And alså do I need a resistor? Are there any soldering to be done on the underside at all?

I have read this thread a number of times. I´m still confused This is my first adventure into this sort of electronics...

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