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Old Jul 06, 2012, 06:47 AM
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Steven
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United States, CT, East Hartford
Joined May 2010
504 Posts
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.
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Last edited by xandrios; Feb 02, 2013 at 08:36 AM.
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