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Jul 03, 2012, 01:26 PM
xandrios's Avatar
I just thought that you were taking the safer route. The way you did it makes it easy to run them in series but also makes it more dangerous if a problem should occur with the PSUs. If you take the proper precautions then you should have no problems.
Last edited by xandrios; Jul 03, 2012 at 01:45 PM.
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Jul 06, 2012, 06:47 AM
xandrios's Avatar

Dell 1850 AA23300 PSU and Astec DS550-3 voltage control modification.

Dell 1850 AA23300 PSU and Astec DS550-3 voltage control modification.

The Dell 1850 AA23300 PSU(550w) and Astec DS550-3 lack the external voltage sense pins(+12V Sense and +12V Return Sense)

that are required for voltage adjustment of the main 12V output.

This easy modification will connect the internal +12V Return Sense(also called -Ve Sense or Vs-) line to external pin D3.

Output voltage is now adjustable from 12V-14.4V(OVP). Usable voltage range is 12V-14.2V.

Regulation is rock solid as output voltage will rise ever so slightly with load.

I've connected this Sense line to pin D3 because the +12V Sense Return pin is usually located at position D3 on similar PSUs.

You don't need to connect the internal Sense line to pin D3. I just did it this way for convenience.

Connect a 1k -10k pot for voltage increase with clockwise rotation. Left leg to pin C3. Center wiper to pin D3. Right leg to pin D4.(For an upright pot)

If voltage is adjusted above 14.4V then the OVP(Over Voltage Protection) will simply shut down the PSU.

P.S. To slow the fans down to a moderate level simply wire them in series and connect them to the main DC output.

There will be 4 power wires that come from the fan combo unit. Red+ and Black- from one fan. Orange+ and Grey- from the second fan.. To wire the fans in series just connect the Orange and Black wires together. Then connect the Red wire to the 12VDC output. And connect the Grey wire to DC ground..

If fan noise is not an issue then just leave them as they are.
Last edited by xandrios; Feb 02, 2013 at 09:36 AM.
Jul 06, 2012, 12:51 PM
Use the 4S Luke
feathermerchant's Avatar
xandrios - I'm curious as to why a 0-3.3V signal to the 12V sense works. It seems like it would require a 12V signal.
Jul 06, 2012, 01:48 PM
xandrios's Avatar
Hello feathermerchant.

You're probably thinking of the +12V Sense line.

A PSU has two sense line.
I used the +12V Return Sense(also called -Ve Sense or Vs-) line that is connected to Ground by default.
Connecting this Sense line to ground yields a base voltage of +12V.
Any change in voltage to the +12V Return Sense will cause the main DC output voltage to change by the same amount.


-1V to pin D3 = 11V
0v to pin D3 = no change(12V)
+1V to pin D3 = 13V out
+2V to pin D3 = 14V out
+2.4V to pin D3 = 14.4V out
+3.3V to pin D3 = 15.3V and will cause the PSU to go into OVP.
Last edited by xandrios; Jul 18, 2012 at 05:56 PM.
Jul 06, 2012, 04:02 PM
Nelapaty's Avatar
Xandrios, thankyou thats just fantastic
Jul 06, 2012, 04:11 PM
Registered User
Would you be able to use this modification if you have two psu's connected in series? ( I have two dell poweredge 7000814-0000 they only have a output of 11.9v each)
Jul 06, 2012, 04:18 PM
xandrios's Avatar
Hey LiftOff.

Yeah. It shouldn't be a problem. All you have to do is find an internal voltage sense line and tap into it.
Last edited by xandrios; Jul 06, 2012 at 05:49 PM.
Jul 09, 2012, 04:09 AM
Registered User
I got 2 HP dps-1200 power supply, I want to use Current Share function, which pin I have to connect together?
Jul 09, 2012, 07:56 PM
xandrios's Avatar
Hello bg1dcg.

Your best bet would be to send DSW a private message. He has some good experience with this PSU.
Last edited by xandrios; Jul 09, 2012 at 08:48 PM.
Jul 09, 2012, 10:38 PM
Registered User
Many thanks Xandrios:
I want to find the pin for Current Share, Any advice will be highly appreciate.
Jul 10, 2012, 11:22 AM
xandrios's Avatar
Hey bg1dcg.

You can find the current share for yourself if you already have your PSU up and running.
Jul 10, 2012, 11:30 AM
Lipo Power
BrushlesHeaven's Avatar
Hi Guys
Sorry to squeez in here but would you know or someone that may know the pinout of KX823 dell power supply? I have one and would like to use it with my chargers....
Jul 10, 2012, 11:47 AM
xandrios's Avatar
Hello BrushlesHeaven

pete236 was able to get his Dell A930P-00 (same PSU as KX823) power supply to run for a short time by connecting pins A1 and B6 to ground.

You might want to PM him to see if he was ever able to get it to run properly.

If a no start then try pins A1 and A6 to ground through a 500Ω resistor.
If a no start then try pins A1 and B4 to ground through a 500Ω resistor.
Last edited by xandrios; Jul 10, 2012 at 11:55 AM.
Jul 11, 2012, 02:56 AM
Registered User
Hi guys, I have a power supply Supermicro PWS-721P-1R for inclusion in the network switch is turned on and turned the block, at first loud fan starts and then slowly turns, there are five on duty, after the closure of PON on the ground floor on the second unit starts - the fan starts to spin rapidly and there + 12V at the output. And then it all stops that tell me?
Last edited by mastermakc; Jul 12, 2012 at 12:10 AM.
Jul 11, 2012, 06:45 AM
Registered User
hello all again

any body are infos for this PSU ?
for running for 12V for my hobby Radio Amateur

many thanks

laurent on2vhf from Belgium

Originally Posted by on2vhf
hi all i am 2 PSU

ESP 117

and pse for help for running 12V


laurent on2vhf

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