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HomeRC & Power✈️Aircraft🚁Helicoptere-Electric Battery-Charger-pSupply › Mod to quieten HP server PS
05-30-2011 05:28 PM  9 years ago
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apostolosnt

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Athens, Greece

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Mod to quieten HP server PS
I guess it is common sense but: This is electrical equipment that you should not be modifying and if you do, you're doing it at your own risk of damage or injury.

I have been using a dual HP 575W power supply setup for charging at home. The PS are quite loud and in general annoying to have them on for 2-3 hours charging.
I started to think that a lot of that air being pushed may not be required to actually cool the PS but it would also serve as general venting of warm air from inside the server rack in the PS original application.
Since now there is no need for that we can even reverse the fan to suck air from the back and vent it in the front i.e. screw the fan on the case so that the side with the writing faces out.
I did that on one of the two PS and I found that this setup would work better. I slowed down the fans with a 20ohm resistor and put the the PSs on load (est. 820W) for 1+ hour charging. The reversed PS case was 1-3 deg C lower!
Seeing that I went even further and used a 68ohm resistor which makes the PS very quiet.
Same test as above (ambient at 24C), PS case at max 27C and the air being blown out never exceeded 33C (91F). So this justified the mod you see below.
I added a switch though to speed up the fans if needed (I live in Greece where summer ambient can be 40+C).
So two resistors used: 68ohm (quiet) and 33ohm (less quiet). 3W resistors are used for peace of mind.
I have done 5-6 charging sessions (takes me about 3 hours to charge all my bats) and everything works perfect.

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05-31-2011 12:34 AM  9 years ago
willanyone1

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Griffith, IN U.S.

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thats pretty sweet i will be getting the same setup in a week, I will have to try it out. Still dont totally understand how you disable one of the grounds?
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05-31-2011 08:30 AM  9 years ago
apostolosnt

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Athens, Greece

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The ground is the mains ground that goes on the PS case. At the same time the neg on the DC side is also connected to the case => ground.
To "float" the DC circuit you need to remove the ground on the DC side. This way you maintain the AC ground.
Basically the PCB grounds to the PS case with two screws at the fan end. You cut the PCB copper on the board that goes there.
Be careful not to damage other lines on the board.
You can also do it by using plastic washers for those screws but I do not trust that. Cutting the copper is 100%.
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05-31-2011 09:25 PM  9 years ago
willanyone1

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Griffith, IN U.S.

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thanx alot caint wait to get this bad boy going. thanx again.
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05-31-2011 11:14 PM  9 years ago
inkspot1967

rrProfessor

Cranston Ri

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all i did to mine was put in a small switch and i can have full speed on the fan for hot days or a lower speed to make it quieter.
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06-01-2011 10:50 AM  9 years ago
apostolosnt

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Athens, Greece

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what kind of switch did you use?
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06-01-2011 12:41 PM  9 years ago
inkspot1967

rrProfessor

Cranston Ri

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Just a small 3 position switch

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06-01-2011 01:59 PM  9 years ago
blackbird

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thessaloniki-Greece

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And how the switch reduses the speed???
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06-02-2011 01:41 AM  9 years ago
inkspot1967

rrProfessor

Cranston Ri

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i forget what wire it was, i think it was a very thin blue wire and it has 5volts for low speed
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06-02-2011 05:01 AM  9 years ago
blackbird

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thessaloniki-Greece

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Ok,now i get it, thanks.
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HomeRC & Power✈️Aircraft🚁Helicoptere-Electric Battery-Charger-pSupply › Mod to quieten HP server PS
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