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Jan 22, 2010, 12:14 AM
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Presumably, when you probe case to DC return blades for resistance, you get an open?

Also, did you check this prior to making your serial connection?

May confirm the theory that it's fused and the fuse blows when serial connection is made without lifting the case ground on the AC plug.

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Jan 22, 2010, 08:23 AM
Registered User
Another option for someone with the "just works" supplies is to disconnect the supplies and then measure the continuity across each fuse to see if either is blown.
Jan 22, 2010, 09:24 AM
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earlwb's Avatar
Well, when I can locate my ground plug adapter plugs. I'll try floating the chassis and see if I measure anything. I can't try it at present until I get a adapter plug or two. I haven't had to use those things for many years, and now I can't find the ones I do have.

Normally these are un-interuptible power supplies used in a computer case in a rack mount setup in a server room. As such the chassis is connected to the AC ground as soon as you start to slide them into the computer case. When the recessed enable pin makes contact then the power supply is enabled. Then when someone flips the power switch on the front of the computer case, the power supply turns on. Both supplies run in parallel all the time. if one supply shuts down due to a fault, the other power supply has to take over.
So technically the power supply chassis or case is grounded all the time anyway.

It is possible that if the chassis is floating and not grounded it may float up to 12v due to stray capacitances inside the power supply. But I haven't tested for that yet.
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Jan 22, 2010, 10:01 AM
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everydayflyer's Avatar
Let's play what if,shall we?

What if there is a fuse(s) which gets blown when the two are placed in series and the cases touch,or both earth grounds are used....................
so this fused blows but the power supplies continue to work and now the cases are connected to a earth ground so what is the problem other than why?

Jan 22, 2010, 10:06 AM
Registered User
Understand and agree to a certain degree Charles. I still believe that it's worth pursuing and understanding because at present it is unknown if there are other more critical safety features of this particular power supply that are served by this same grounding mechanism (assuming that the fuse theory has merit).

Jan 22, 2010, 10:37 AM
Southern Pride
everydayflyer's Avatar
Yes it may prevent damage to a very expensive server or such.

From my point of view the ungrounded case may be come hot series connection issues have never been a real issue.

With the IBM 235 if you connected both grounds or the cases touched they shut down requiring a re boot. These hp will function as desired for our purpose with cases grounded. Unless I mis the point of this Thread this was the issue.

Looking forward to the ultimate outcome of the investigations.

Upon a close visual inspection (without opening the cases)it appears that F 1 is indeed blown on my units. I will leave it to others to determin the worth of this knowledge.

Last edited by everydayflyer; Jan 22, 2010 at 11:09 AM.
Jan 22, 2010, 10:55 AM
Hello all,
First let me say I am in no way qualified to provide any intellectual input into this conversation. I'm providing my observation and or experience and hope it might contribute.
I did check my grounds prior to hooking up my two HP power units and compared them with a Meanwell knock-off PS made by MW power in China.

AC grounded to case.
V- No continuity to case.
AC grounded to case.
V- Continuity to case.

Just now after power up with jumper lead for 24V:
HP1 (the one I pull 12V+ from)
AC grounded to case.
V- CONTINUITY to case.

HP2 (the one I pull 12V- from)
AC grounded to case.

Because I use a jumper lead and move the PS's about, (sometimes I just use one), I am not sure 1 has always been 1 and visa verse.
Jan 24, 2010, 10:10 AM
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earlwb's Avatar
OK, I ran some more tests. This is using the DL580 server power supplies discussed elsewhere.
My second power supply shows zero ohms from the power common pins to the chassis. But my first power supply reads a open between the chassis and the common power pins.

Power up the power supplies, with the AC ground pin open to the house ground, and the second power supply reads zero volts on the chassis as well as zero volts on the chassis for the first power supply.

Now connecting the 12v positive pins from the first supply to the second supply negative power pins, results in the second supply reading 24v on the positive power out pins. This also results in the chassis on the second power supply reading 12v on the chassis then in reference to the common on the first power supply.

But it is odd that with both power supplies grounded and reading, more or less, zero ohms between the two chassis, that you can measure 12v on the chassis of the second power supply when they are setup as a 24v pair. But if you connect the chassis together then the first power supply chassis also reads 12v on it how too. You would think having 12v on the AC ground pin would cause a circuit breaker to trip or something, but it didn't. So maybe my house isn't wired all that good still.

Now a few days ago, I thought I had measured a open between the common power pins and the chassis, the same as the first supply. Maybe I was mistaken, I don't know now. I must have only measured one power supply between the common power pins and the chassis and the green AC wire.

So in any case, it is probably wise to let the second power supply float on the AC green wire, and ensure that the chassis on the two power supplies don't touch or make contact to each other. One never knows when the power return lines might wind up having contact with the chassis for some unknown reason.

Now this is only a issue, if you are planning to use the power supplies in series to get 24vdc out of them.
If you are only using them as a 12vdc power supply, then this is a non-issue, and is not a problem.
I hope this helps people out. if it makes sense to anyone besides me.
I sorta wonder if there were two versions of this powersupply or not. One with the DC power lines not connected to the chassis ground and one version with the DC power lines connected to the chassis ground.

I did take apart the one supply that had the chassis and DC return lines connected. The two fuses were fine, no opens. I disconnected the top half section from the bottom section and found that the DC to chassis connection is somewhere on the bottom half section of the power supply. But that was as far as I went with it.
Last edited by earlwb; Jan 24, 2010 at 11:13 AM.
Jan 25, 2010, 09:57 PM
Registered User
Ordered 2 DL580's today. I will check the DC- to see if is connected to the case and report back.
Jan 26, 2010, 12:21 AM
Electric Helis is my game
MrMel's Avatar
Meanwell's are rated for series use, anyone that has two and can connect them in series to see how they compare?
Jan 26, 2010, 03:28 AM
ancora imparo
jj604's Avatar
Thread OP
Don't want to be a pedant but just so no one finds they have the wrong supply.

DL580 is an inadequate description if you are buying one of these from someone other than Trademoon. There seems to be plenty of different supplies that fit 580 series servers.

The smaller noisy 12V 100A one I converted is fully titled:


The part number is critical. The label on the case has a couple of different numbers

Part Number 3378676-501
Spare number 406421-001

The bigger, quieter one with the 12v 55A and3.3v 45A rails discovered by earlwb that you are talking about here is on the left in this picture posted by kit. The 100A one is on the right.

Make sure if you want the bigger one that's what you are getting. It's a:

HP 800W Hot-Plug Redundant Power Supply Proliant DL580 G2 NAS E7000 v2.

The part number on the label for this one is 192147-001 and 192201-001 as a spare part. I suspect it is also known as a 278535-B21.

Originally Posted by dfrazier
Ordered 2 DL580's today. I will check the DC- to see if is connected to the case and report back.
Jan 26, 2010, 10:13 AM
Registered User
I purchased the ones from trademoon that have been talked about.
Jan 26, 2010, 11:21 AM
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earlwb's Avatar
Those things are selling fairly fast. When I started my separate thread about them a while back, there were over 118 of them in stock at Trademoon.
Now they are down to 47 at this moment.
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Jan 26, 2010, 11:37 AM
Registered User
Originally Posted by earlwb
Those things are selling fairly fast. When I started my separate thread about them a while back, there were over 118 of them in stock at Trademoon.
Now they are down to 47 at this moment.
I noticed this also. That is why I ordered them. I placed my order yesterday and they are on a truck for delivery today.
Jan 26, 2010, 02:27 PM
Registered User
I just received my power supplies. I just checked and both of them show 0 ohms between ground and the case. I guess I will have to keep them from touching until myself or someone here can figure out how to unground the case.

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