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Feb 13, 2013, 06:41 PM
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still4given's Avatar
I wanted to mention something that we talked about on another thread and that was a discussion about lifting the DC ground on both units when setting up to run them in series. It was my opinion that it didn't matter if both were lifted or not. Well, wen I converted this pair of DSP-835AB power supplies to use at a 24V I went ahead and lifted the ground on both while I had them apart. When using my DVM to test it I got a spark when I touched the case and DC ground lug at the same time. Well I checked to see if I had any current between the two and didn't read any DC voltage, however, when I checked for AC ripple I got 35V AC. Now I don't know how much current there is because I don't have a way to test for that but it is enough to cause a small spark. So, from now on, I will leave the first unit with the DC ground attached to the case.
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Feb 15, 2013, 04:25 AM
Registered User

A few Questions On Conversion...

Hey Terry,

Thank you so much for your help and insight. Your are appreciated.

I got my PSU's today. I'm currently working on the 24v (2nd PSU with floated DC ground). I have a few questions.

1.) I have separated the PCB from the metal housing. I see the two cladding that you were talking about. Only the cladding near the rear (fan side) has the metal circle traces above and below on the PCB where the screw hole is. Should I dremel the cladding off or use a nylon screw and washer?

2.) With my glasses on and a led bright light I cant find pins 3 & 4 on top of the PCB. All of the lines come out of the molex connector and then kinda curve over them selves to the top of the PCB. I looked under the PCB and I see the leads but I have no idea which ones are 3 & 4. Is it safe for me to plug in the PSU then tap the connections with a little jumper wire until it turns on? Is there a better way? I would like to keep my eyebrows

3.) Any ideals on how to locate pins 17 and 19? Id like to put in that pot to adjust output voltage.

4.) If I decide to remove the molex connector from the PCB (to solder connections from the inside) what is the most graceful way to do it without damaging the top of the PCB?

Thank you all
Feb 15, 2013, 11:09 AM
Registered User
The pins are numbered in the pic from this post:
Feb 15, 2013, 04:39 PM
Registered User
Thanks herold, I've seen that post but I don't understand how to find those pins on the other side of the Molex connector or how to find those pins under the PCB, I'm going to try to figure it out using continuity pin by pin but the traces are so small inside the Molex connector. Where did you solder from? Under the PCB or on top?
Feb 15, 2013, 04:44 PM
Registered User

also odd...

Also when I look at the Molex PDF pin out it has 32 pins on the signal connector and our signal connector only has 24 pins

Feb 15, 2013, 04:50 PM
Registered User
Sorry, I misunderstood.

In my case I used pliers to break off the plastic around the pins, it actually worked surprisingly well, broke off the tip but left the pins exposed. Did the same for the 12v as well. My next plan is to snip all the pins except 3/4 and 17 for the pot.

I did start but trying on the pcb, and just counted them out to find what I needed. Turns out my soldering skills aren't sufficient for such a confined space.

I think a voltmeter would allow you to determine which pin is which point on the pcb.
Feb 15, 2013, 05:02 PM
Registered User
So you see what I mean:
Feb 15, 2013, 06:36 PM
Sky Pilot
still4given's Avatar
I must say, I didn't realize that there were 24 pins in the small molex plug. From the top of the PCB I could only see 12 blade looking wires and assumed that was it. No wonder when I tried to solder together the 3rd and fourth blades it didn't work. Those were pins 15 & 16. I stuck my soldering iron tip down in between those two blades and was able to get the unit to turn on and then flowed some solder in and it worked. Now that I see what is there, it is likely that I may have included pins 15 & 16 in the mix. It is working fine but i can"t help but wonder. I'm going to do a continuity check and see if that happened. I'll report back when I know.
Feb 15, 2013, 08:11 PM
Sky Pilot
still4given's Avatar
OK, I checked and as suspected, pins 3, 4, 15 & 16 are shorted together. I don't know what 15 % 16 do but so far all seems fine so maybe I lucked out. One good thing is now I know where pin 17 is if I decide to add a voltage control.
Last edited by still4given; Feb 15, 2013 at 08:19 PM.
Feb 19, 2013, 09:03 PM
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still4given's Avatar
I pulled mine apart again today to tinker. I soldered in a 1watt 10ohm resistor to the fan. It reduced the fan speed a bit but with two of them running it is still fairly loud. Still going to be an outside PS. Next, I soldered a 1.3kohm resistor between pins 17 & 19. That raised the voltage output to 13.2V. While I was in there, I reconnected the DC ground to the case in one of the units. Feeling optimistic, I hooked them back up in series for what is now a 26V PS, and hooked up my PL8 and a couple 6S packs and started a 40A charge. It started out OK, but shortly, the charge rate started to drop and then began to fluctuate as did the PS output. The longer I watched it the worse the fluctuation got so I shut it down. I opened them back up and pulled the 1.3K resistors and hooked it back up.The charger now held a 40A charge but the PS still varied slightly. Xandrios stated this; "You need to solder the DC power wires/cables directly to the mainboard.

Voltage regulation will be near perfect once this is done."

That may explain the fluctuation but I'm not keen on trying to solder to the main board since it consists of several small solder points. I may just live with the fluctuations since they are not that bad. I'm not sure if the bad fluctuation was caused by the increased voltage making it unstable or if the increased voltage exacerbated the problem of not soldering the output cables. I don't need the additional voltage so I'm leaving it alone. I just wanted to share what I found in case some of you were thinking of raising the voltage.
Feb 23, 2013, 11:32 PM
Sky Pilot
still4given's Avatar
Hi Guys,

Well I've learned a couple of things. I ordered two more units and when these came I went ahead and pulled the PCB completely out of the case so I could take a look at things. I see now that the center output slot actually has both the + and - rails. This should work nicely for 12V outputs by creating a "plug" with a double sided PCB board like in post #3. Should be able to just solder a + lead to one side and a - lead to the other. I'm going to give it a try.

While I had the board out of the the case it was quite simple to just create a solder bridge across pins three and four on the bottom of the PCB. Also, I had soldered in a 10ohm resistor in the fan circuit to quiet the fans but it wasn't quite enough. The fans were still pretty loud, especially compared to the DPS-600PB. So today I tried a few different values. A 33ohm wouldn't spin the fan. The 22ohm almost seemed too slow but then I tried hitting the heatsinks with a heat gun and the fan spun up to what sounded like full speed so I am going to give it a try with a big load and see if it runs cool enough. It will be easy enough to wire in a switch if it seems like it may need to be overridden on a hot day or with a big load. I'm hopeful that it will be fine like this because this is nice and quiet now.

Blessings, Terry
Feb 24, 2013, 11:56 PM
Sky Pilot
still4given's Avatar
Well good news. The fans spin up as the unit gets warm from the load of driving my PL8. I ran it for over 1/2 hour at 46A and it was just barely warm. The fan gets a bit louder as you would expect but once the charging is finished the fan begins to slow back down until it is nice and quiet again. I'm pretty pleased with this PS. I don't know how it acts when closer to it's rated limit since I don't have anything to load it that high but at below 50A output, it is very stable and cool.
Feb 27, 2013, 03:40 AM
Registered User

Thank you all!

I'm finally done with my PSU.

If anyone is interested its here:

IBM 835 Watt Server Power Supply (6 min 53 sec)
Mar 15, 2013, 04:27 PM
Registered User
Still4given....Where did you wire in the 22ohm resistor (from where to where)? What wattage was the resistor?

I have the Artesyn unit and have the unit wired up, but would like to experiment with the fan loudness, as most of the time i will only be drawing a 10A load.
Mar 16, 2013, 12:27 AM
Sky Pilot
still4given's Avatar
I just cut the red wire going to the fan and inserted a 22 ohm resistor. I tried a 33 ohm but the fan didn't turn. I didn't try putting a load on the PS to see if it would come on as the temp went up. I may try that sometime. These fans have an annoying sound. Even at low rpm, they are still more grating than the DPS600 fans.

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