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-   -   Dell poweredge 2600 power supply nps-730ab (https://www.badcaps.net/forum/showthread.php?t=80142)

cashkennedy 10-18-2019 09:09 PM

Dell poweredge 2600 power supply nps-730ab
 
8 Attachment(s)
I haven't touched this server in like 6 years and I was getting ready to throw it out but figured id make a backup of the data on it.

It had been connected to power but not actually switched on for a few years (would have unplugged it if I had noticed). Worked last time I used it a few years ago. Im guessing the startup cap went out, and its not really worth the money or effort for me to go much further then that to fix this (why im not just buying a power supply on ebay for $40)

Anyways trying to figure out which cap is the startup cap. Its been a while since I worked on a power supply but the startup cap has to be on the hotside? should be close to the pfc IC?

The cap inbetween the 2 heatsinks is c3 a UCC KME 25v 47uF (in between the smaller heatsink with bridge rec and the large heatsink with mosfets)

the caps on the small vertical board next to the transformer are:
c511 maybe a lelon? 50v 4.7uF
c518 ucc KME 25v 47uF
c15 25v 100uf
c26? same as c518 I think, cant really read it where it is placed
c12? ucc SMG 16v 100uF

So am I right that its probably the startup cap, and which cap do you think it is? If you need / want better or more pics just tell me what area.

cashkennedy 10-18-2019 09:15 PM

Re: Dell poweredge 2600 power supply nps-730ab
 
I didn't do a lot of traditional diagnosis on this, maybe I should go back and do that, but these have 3 led built into the power supply that equal: plugged in, turned on, and fault. None light up. This power supply also as far as I can tell only creates 12v power which the mother board converts into other voltages, and also a standby voltage that the motherboard uses to at least turn the power supply on. I don't think theres many markings anywhere about where the standby leaves the power supply and theres around 15 small pins on the back that communicate with the motherboard, but I guess I could test them all for voltage with the power supply plugged in. Which is all an ordeal to test since you have to have the power backplane involved.

cashkennedy 10-20-2019 12:40 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
I tested all the outputs and didn't get anything over a volt.

The caps I mentioned above all had ~ 60v to neutral of the AC input. (around 22v to ground, but my house has some bad wiring where ground vs line is like 56 volts. , so in other words ground isn't very reliable for voltage testing)

Shouldn't the power to the startup caps be more like 180v? that the main capacitors would see?

stj 10-20-2019 05:00 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
the startup cap will see mains x 1.44 via a current limiting resistor

cashkennedy 10-20-2019 07:44 PM

Re: Dell poweredge 2600 power supply nps-730ab
 
5 Attachment(s)
I tested the voltage leaving the bridge and get 160v so that seems ok. Also did diode tests on bridge and got normal readings except 3 readings were 0.478 and the other reading that should match was 0.466 , but probably close enough that I doubt that's the problem.

I decided to just remove the daughterboard that holds the chips that I assume are for the pfc and now I just gotta decide what caps I want to use to replace these. Is it safe to increase the uF on all of these to the nearest thing I have?

Updated list of caps on daughterboard:

C511 LTEC 105c 50v 4.7uF - can I upgrade to Panny KA? 85c 50V 10uF
C518 UCC KME 105c 25V 47uF - can I upgrade to Panny FR 105c 63V 47uF
C15 LTEC 25V 105c 100uF - can I upgrade to Panny FM 105c 25v 220uF
C26 LTEC 50V 105c 3.3uF - can I upgrade to Panny KA? 85c 50V 10uF
C18 UCC SMG 85c 16V 100uF - can I upgrade to Panny FM 105c 25v 220uF


Also included a picture of my handwritten work on deciphering the pin out of the 4x6 connector in the back of PSU and how it translates to the 8x2 ribbon cable that runs to the motherboard from the power distribution board.

Per Hansson 10-21-2019 05:01 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
Replacing all of the tiny caps is usually the best approach.
If you don't want to spend a silly time desoldering and testing each single little cap ;)

cashkennedy 10-21-2019 06:02 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
Yeah I intend to replace all of them, just not sure if I can substitute with the caps I listed above that I had on hand, since I don't have any of those uF values exactly.

stj 10-21-2019 06:38 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
what is the part number on each chip?

Per Hansson 10-21-2019 09:15 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
Quote:

Originally Posted by cashkennedy (Post 921258)
Yeah I intend to replace all of them, just not sure if I can substitute with the caps I listed above that I had on hand, since I don't have any of those uF values exactly.

Some of the values you quoted are quite far off, and I would not replace a 105C cap with a 85C cap.

stj 10-21-2019 09:36 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
i wouldnt go off with values either, the small ones may be for timing or some other critical thing, not power smoothing.

cashkennedy 10-21-2019 07:59 PM

Re: Dell poweredge 2600 power supply nps-730ab
 
If I have to order any caps ill order correct ones for all of them obviously. I was hoping to not have to put any money into this since I just want to backup the data on the server then donate it to local electronic charity where they will throw it in the dumpster. So if there's one cap you suspect most and think I can throw in one of the other caps I have or two of my lesser ones to add up I might try that. I can always remove the suspect cap and test it right, as it would fail even a multimeter capacitor setting at this point.

Anyways chip wise on the front of daughterboard:
IC4 STM L4981A (power factor correction)
IC3 ON LM393N (dual comparator)
ic501 is a mystery chip top line is "2F3" next line is "1001DL" its a 16 pin chip

On the back of the daughterboard is
(no board marking) STM NE556 (dual timers)

There's a small area where the primary side of the power supply wraps around the secondary and there is :
IC901 Power Integrations TOP244Y
i'm guessing the active pfc has to turn on first before this chip then handles the standby voltage rail.

There's a tiny (dime sized) transformer in the primary (not crossing into the secondary) connected to an optocoupler I think. what does this tiniest of tiny transformer do? (just curious, it has nothing to do with my problem)

Per Hansson 10-22-2019 01:10 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
The PFC will not run when the PSU is in standby.
So if you do not have standby voltage present it means the IC901 TOP244Y is not switching on.
So check the capacitor connected to that.
Remember an ATX PSU is actually two power supplies in one: the standby and primary supply.
All controlled via different transformers, the only thing they have in common is the bridge rectifier but you have already confirmed that creates 160VDC which is normal with a 115VAC input.

If this is not time critical why not get one of the cheap "transistor testers" on eBay?
(The one that is really a tiny LCR meter for $10 or sometimes even less?).
I would not want to solder back that daughter board that you have taken out without first confirming the caps are ok or replacing them!

cashkennedy 10-23-2019 12:15 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
The startup cap for the top244y all in one chip that does the standby is 100uF, could i put 2 47uF in parallel for this? And could i test that without the daughterboard (i'm guessing not lol) but yeah i don't want to have to remove the daughterboard again, I did it with about 2 feet of wick since i don't have a solder sucker or hot air station or tip wider then 6mm

What are you suggesting the transistor tester for? Would it allow me to test capacitors while they were still in circuit? Its only 6-7 caps I could just undo 1 leg of each quicker then picking a tester on ebay.

Per Hansson 10-23-2019 03:19 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
Yes, to test the caps.
Obviously if you already have a capacitor tester that tests for ESR too just check them?

cashkennedy 10-28-2019 09:13 PM

Re: Dell poweredge 2600 power supply nps-730ab
 
I replaced all the startup caps, but that didn't help.

I did notice the startup capacitor for the standby supply (power integrations top244y chip) goes from 5.8v to 0v when I read both pins of the cap with my multimeter, then eventually back to 5.8v after a few seconds. The manual says: A hysteretic internal supply under-voltage comparator keeps VC within a window of typically 4.8 to 5.8 V by turning the high-voltage current source on and off as shown in Figure 8.

So I don't know if that would mean there's a short or something inside the top244y chip, but then why would it eventually return to 5.8v every few seconds?

Per Hansson 11-01-2019 11:37 AM

Re: Dell poweredge 2600 power supply nps-730ab
 
Quote:

Originally Posted by cashkennedy (Post 922715)
So I don't know if that would mean there's a short or something inside the top244y chip, but then why would it eventually return to 5.8v every few seconds?

Pretty much every cheap PSU design will retry forever.
Meaning it detects a fault: shutdown, then starts up and tries again...


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