Dell Power Supply NPS-250KB B

[Wester547]

Re: Dell Power Supply NPS-250KB B

Are you getting +5VSB (if some sort of crowbar protection circuit is active that is latching, I doubt it)? That would clue us in to whether it could be a bad startup capacitor or not.

[pig4bill]

Re: Dell Power Supply NPS-250KB B

Bringing back old thread.

I have this Dell, and had read this thread several months ago after it exhibited the power failure behavior as described early in the thread. I unplugged, and it got working again, so thank you for that.

I recently moved, so powered down per normal, unplugged everything, and moved the pc to the new place. It will not come back to life however. I'm probably going to buy a refurb PSU. Any reccos on the best place to get one? Is it likely the problem caps mentioned in this thread would be replaced, or would that matter with regard to the issue of protection circuits not allowing it to power up at times?

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

Just found some more links to add to yours and mine knowledge

Hand written paper notes of moding a supply to output 13.5V for powering a radio.
http://www.webx.dk/oz2cpu/radios/psu-pc1.htm

Lots of information about moding a power supply
http://www.qrp4u.de/docs/en/powersupply/index.htm

http://pavouk.org/hw/en_atxps.html
http://www.epanorama.net/links/psu_computer.html

DNA1002 chip power supplies with Chinese writing. Use Google to translate.
No schematics, just interesting translated to english writing.
http://bak1.beareyes.com.cn/2/lib/20...20709108_3.htm


Hello my name is Fred. I have fixed a couple DELL 250W power supplies. Will look again next time I get to the Shop and take a couple pictures of my own.

Have you thought of using KiCad to create a schematic of your PSU. At least the parts around the feed back circuit. Or paper and pencil and take a picture with a camera. Or Eagle software

http://www.kicad-pcb.org/display/KICAD/Download+Kicad
http://www.kicad-pcb.org/display/KIC...Software+Suite
www.cadsoftusa.com/ Eagle Software to create schematics and layout PCBs

The LM324 is a quad op-amp package, Single power supply voltage.
Used in this circuit to check for over voltage protection ???
www.ti.com/product/lm324


Will work to provide answers to your questions. Might not have some answers. Let me know if those PSU modifications answer your questions.

I am listening, Fred Finster

so the LM324 is used for overvoltage protection, that leaves the dl 1001/2 I forgot the exact number, which is located on the daughter board for voltage regulation, I suppose.
I am not familiar with those softwares, for schematics thou I will look into it,
I noticed that from each power output there are 2 paths 1 to the lm324 one to the dl1001, on the daughter board there are several surface mount resistors, I assume this is the voltage regulation circuit, now where to install a pot and what size I have yet to figure that out.

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

I do apreciate the interest and the input, I shall read up on those new links see if I can figure this out, in short, I am not very good with electronics, couple weeks ago I did not even know what a power supply is made of, I do know electricity and basic princyples, and I have read a fair bit to get familiar,
I have seen some meanwell units that were done, and also some atx, figured this one should be no different thou it seems to be a bit more complicated, if you would indulge me. what do all these stand for:
asic, pwm, pfc bit new to me.

[PeteS in CA]

Re: Dell Power Supply NPS-250KB B

The IC marked "1001" is an ASIC made for Delta Products that, IIRC, combines a 384x-type PWM controller and a 3854-type PFC controller. There might be another ASIC on the secondary side marked "1002", which does supervisory and protective functions. Judging by the date code on a transformer, that was built late 2002 or very early 2003.

[WB7ODYFred]

Re: Dell Power Supply NPS-250KB B

Just found some more links to add to yours and mine knowledge

Hand written paper notes of moding a supply to output 13.5V for powering a radio.
http://www.webx.dk/oz2cpu/radios/psu-pc1.htm

Lots of information about moding a power supply
http://www.qrp4u.de/docs/en/powersupply/index.htm

http://pavouk.org/hw/en_atxps.html
http://www.epanorama.net/links/psu_computer.html

DNA1002 chip power supplies with Chinese writing. Use Google to translate.
No schematics, just interesting translated to english writing.
http://bak1.beareyes.com.cn/2/lib/20...20709108_3.htm


Hello my name is Fred. I have fixed a couple DELL 250W power supplies. Will look again next time I get to the Shop and take a couple pictures of my own.

Have you thought of using KiCad to create a schematic of your PSU. At least the parts around the feed back circuit. Or paper and pencil and take a picture with a camera. Or Eagle software

http://www.kicad-pcb.org/display/KICAD/Download+Kicad
http://www.kicad-pcb.org/display/KIC...Software+Suite
www.cadsoftusa.com/ Eagle Software to create schematics and layout PCBs

The LM324 is a quad op-amp package, Single power supply voltage.
Used in this circuit to check for over voltage protection ???
www.ti.com/product/lm324


Will work to provide answers to your questions. Might not have some answers. Let me know if those PSU modifications answer your questions.

I am listening, Fred Finster

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

found this http://www.thebackshed.com/forum/upl...10459_1002.jpg does it mean anything to anybody?

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

so i suppose nobody knows any better, as to where the voltage/curent is regulated on these units, guess I'll give it a go see what happens

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

I'm either on my own, you all think I am nuts and about to fry myself, or got no good advice ( i'd like to doubt that last one ), or maybe I am just beating a dead horse.
I gave up trying to find a schematic, there just isn't one, nor a datasheet for anything on this unit, must be an industry secret, so in lack of other options, I have been tracking the circuit board trying to understand it.
based on the little theory I know, I noticed 2 paths, from each output, one to the sister board one to the optos, the 5v and 12 v make it to the sisterboard untampered, the 3v goes through a resistor gets reduced to 1.35v,
as for the optos, the 12v has a direct path, to the one on the edge, the 5v and 3v, go through some jumpers up to some sesistors, which past them I get some noise as soon as I touch the rester lead, so I haven't messed with it too much.
I learned the opto's are part of the feedback ( voltage regulation ) so I asume that is the path voltage gets regulated, that beeing said guess the sister board has something to do with curent regulation, too much guessing that is for sure, hope this is helpfull to the OP, doesn't mean much to what I am trying to acomplish.
one thing I do not get the atx examples I came across, they were regularing all outputs with one pot, seems these feedbacks have separate paths for each output, every example I seen is different and each has their own method, guess all these paths come together at some pint and that is where the mod is done.
sure hope one of you's has a clue, I am back to thinking electronics are disposable

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

ok so I figured out what an opto coupler is supposed to look like, and I think I found the 4 in question, see pics, there are several resistors leading up to them, but which one is which beats me,
that beeing said, based on some generic diagrams and schematics I came across, the chip to the left is the controller? I tried checking voltages on it before, but looking back I think it operates in ac, it is on the highvoltage side, wasn't getting any readings dc.
what am i looking at here? changing the resistor values before the optos, would change working parameters, I think, that I learne so far is the feedback circuit, 3 outputs voltages, is the 4th for the amps?
does anybody have a clue? no luck finding any info on this board nor chips for that matter.

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

http://www.youtube.com/watch?v=mK_rIs7uFlo
here's another example, for some reason they are all atx, not that I could make much out of the video, but that is the Ideea I am trying to accomplish, for some reason, with 1 pot he can regulate all output voltages, I know for the most part a voltage regulator is controlled by 2 resistors, a pot could make that adjustable, now little that I know, I would say the pot max resistance should be about the same as the 2 stock resistors, if wired right should be able to vary the resister values, therefore adjust the voltage
hope I am not hijacking here but it was the same model and conversation already led to some of the components I was looking at, that's how I found this thread

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

oh and I touched some of those surface mount resisters on the daughter board with a screwdriver, the draw from the extra metal was large enough to cause a voltage drop, to 8v on the 12v output, unlike other silly experiments, it did not trip the psu, as soon as the screwdriver was removed voltage went right back up. therefore I feel I am on the right track but again this is not science, pocking things and see what happens.
there is also a meanwell supply mod that I read about that inspired me to tinker with this
http://endless-sphere.com/forums/vie...l+mods#p653187
different animal but same principal, if only I knew which resister regulates the amp output on this newton unit, should be able to accomplish the same.
there are plenty examples converting these units to a bench supply but not so much about making the output variable.

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

bump.

I know there is a wealth of knowledge among your circles, and what I am trying to accomplish is a bit unconventional to what you boys do for fun, I could use some insight here before I do something silly and blow this thing up, I took some pics and poster them here http://s1365.photobucket.com/user/20...?sort=3&page=1
I am not sure what the chip on the main board does but I measured some voltages and this is what I got:
voltage readings, starting at pin #1 top left, they changed a bit by the time I wrote them all down, I am sure some of my outputs did as well, I shall doublecheck on that.
1 = .52v
2 = 11.85
3 = 11.84
if I know better I would say this is where the 12v is beeing regulated
4 = 17.24 sounds like v+
5 = 2.49
6 = .52
7 = 16.23
I would say that is simmilar to the adjustable voltage circuit I seen on some of the atx chips
8 = .5
9 = 4.95
10 = 4.94
this looks like the 5v regulating circuit
11 nothing, must be ground, I'll doublecheck
12 = 3.27
13 = 3.28
14 = .6
it is labeled lm324n, found this for a datasheet not even sure if it is the right thing https://cdn.badcaps-static.com/pdfs/...c4e67ba06d.pdf
for a minute I thought it was controlling the output voltages, now I look on the sister board I have the dna1002e it has all sorts of voltages going to it and I see some paths on the main board from the outputs to it I am assuming this is the feedback circuit, goes to show how much I know,
Honestly I am a gearhead, electronics for the most part I regarded as too complicated and disposable, I do know the basics, thou I never had much luck with them.
I know it can be done as I have seen some examples on youtube:
http://www.youtube.com/watch?v=rpUk9hpFQL4 this guy done a few but he knows his stuff and had schematics, I have neither
also: http://www.youtube.com/watch?v=rkApRg5VWnc another good example
now both aimed at the 12v circuit, I need 3.65v, no need for a range from 2v to 30v, one thing I am unclear of:
I read that some of these power supplies have individual feedback for each output, the examples I seen had 1 pot controlling all outputs, also not sure if the output amperage can be adjusted, I am sure that there is a circuit that regulates it, and the mods are probl as simple as replacing 2 resistors with 2 trim pots, 1 for voltage one for amps, but which ones? and what size 2k seems to be the norm.
I also read about the opto couplers, I read somewhere this unit has 4, I know what they are, read about it, no clue what they look like, would help identifying the feedback circuit and the resistor to be replaced with a pot, I'll have a look again when I get home.
if any of you know more than I do ( and you must since I don't know much ), a schematic, advice pointers, I'll take anything, by all means please enlighten me, I read the theory, cant really place it on the board.
also there is a small white pot, it was glued fix, I tinkered with it, it did noy change anything that I was monitoring, what does it do?
all thoughts are appreciated.
George

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

Do you mean that it's working but you're trying to improve upon the voltage regulation? I wouldn't be worried about the voltage regulation on any of the rails unless it's out of spec. Unless you need to because you're using the PSU for other means (if I read correctly). The amp output should be as the label says - 18A on +3.3V, 22A on +5V, 14A on +12V, 1A on -12V, 2A on +5VSB, 170W for +3.3V and +5V combined maximum, 250W maximum.[/QUOTE]

not necesarrely improve, more like change, and yess you guessed right, the supply was working perfectly fine when I got it, still does, well my knowledge is limited but it works fine best I can tell, however I did buy if for different purposes, I have these lithium batterypacks with some issues, I need to weed some bad cells, in order to do that I need to charge and discharge them individualy to see how they behave,
longstorryshort without going too far off topic, I need 3.65v at 10amps, now I know batteries are a bit funny and draw whatever they need so I am a bit in the dark there but for now I would be happy if I figured out how to tamper with the feedback, and lie to it thet the 3.3v is low so that it will give me 3.65 in return or step down the 5v ( the dummy load is on that so not sure how that would interact, not in a desktop unit), I traced the back of the board and I see that there is a line from the 3.3v output going through a resistor to the sisterboard, figured a trimpot might do the trick as I have measured the voltage across that resistor, 3.35 goes in, 1.xx comes out, I have seen some other mod examples for atx but they have different chips, can't find a diagram on this one nor a datasheet for most these chips.

once I figure that out, I would like to limit the output to 10 amps, preferably make it adjustable, thou all this is well beyound my skill, therefore I need some help

[Wester547]

Re: Dell Power Supply NPS-250KB B

Main switcher is a Fairchild FQA7N80C.

Mine has 2SK2746 from Toshiba as its main switcher, but like yours is rated for 7A/800V@25*C (same switcher to be found in those Dell 200W Newtons), so it probably cross references to it. A bit on the inefficient side but it does seem good for 250W so I won't complain (I have seen similar grade FETs in Bestec 250Ws, like STW7NC90Z), especially given the heatsink it's soldered to and the amount of air the Sunon sleeve bearing fan pushes. Also happens to have the same rectifier for the -12V rail as yours, I had mistakenly said Panjit because I was looking at the bridge rectifier at the time (GBU 8K from Panjit Semiconductor without a heatsink). I think B20100 has more to do with the +5V rail. The +12V rail schottky wise is too overspec'd to need anything more. I wouldn't be surprised if B20100 was freewheeling for +5V and MBR3045CT was rectifying.

what looks like a SOIC-8 SMT IC

Is that UC3843B?

This may not have been my best choice for a mod but it was reman for $5 so it will do.
any input much apreciated

Do you mean that it's working but you're trying to improve upon the voltage regulation? I wouldn't be worried about the voltage regulation on any of the rails unless it's out of spec. Unless you need to because you're using the PSU for other means (if I read correctly). The amp output should be as the label says - 18A on +3.3V, 22A on +5V, 14A on +12V, 1A on -12V, 2A on +5VSB, 170W for +3.3V and +5V combined maximum, 250W maximum.

[2007blueprius]

Re: Dell Power Supply NPS-250KB B

DNA1200E would be for secondary side overcurrent protection (I don't think that's causing the OP's problem, but you never know), etc. 1500uF + 470uF for the +12V rail... that's it? That seems really low coming from a PSU brand that knows how to make even underpar capacitors last ages. I have a Newton Power (NPS-250GB, Rev 01 B, datecode 0142) that also has a 470uF, 25V Rubycon YXG for -12V filtering (as well as L7912CV mounted to the other side of the heatsink and Panjit ER802 without a heatsink as its rectifier, I think), but all the other output capacitors are Ltec LZG and unfortunately the small capacitors are Ltec TK... voltage doubler has Nichicon LU though... it probably still works after 20,000 hours and 5,400 cycles of use because the Sunon sleeve bearing fan it has blows out a stunning amount of air and the heatsinks are very good and thick. It never really spits out hot or even warm air. It probably has the same configuration as yours (2200uF, 6.3V x2 for +3.3V and +5V, 2200uF + 470uF for +5VSB). Mine only has 3 optocouplers, though, and the only other PCB in the PSU is the input filtering PCB.

I find the 1500uF + 470uF configuration confusing because even older (albeit proprietary) Dell Newton 200W power supplies have more than that on the +12V rail, 2200uF, 16V Chemi-con LXJ + 330uF, 16V Rubycon YXF, though there's no PI filter or shunt to be found on that rail. Do you remember what the rectifiers were on the secondary side of the PSU, as well as the main switcher, if you checked? Also, I don't mean to derail this thread away from the OP's problem, so I'm suspect that either the 4th optocoupler is configured unfittingly or one of the small startup capacitors - a Ltec TK or Taicon VT - failed.

I am tinkering with the exact model and quite honestly I don't know exactly what I am looking at, but I am trying to get the voltages slightly adjusted, preferably the amp output too, problem is I am kinof clueless, haven't been able to find a diagram I am guessing,
up untill I cam across this post I thought the dna1002e on the sister/daughter board might have something to go with voltage regulation, I see there are lines comming from all 3 outputs to it, the 3.3v goes through a resistor, the 5 a jumper, and 12 goes straight into pin 2 I believe it was, led me to believe that was the feedback circuit, I am realy not too good at this stuff.
either way you all semm to know a bit, can any suggest as to how I could go about adjusting the voltages and current output?
I am aiming for 3.65v at 10 amp preferably, idealy I would like to step down the 5v output to well below spec, I am looking to build a single cell lithioum charger for testing individual cells, charging and discharging, I could charge 2 cells at once to split the amps, but that would defy the whole point I am afraid, I would like to be able to monitor these bateries individually,
This may not have been my best choice for a mod but it was reman for $5 so it will do.
any input much apreciated, also, what is the small white trimpot for? tinkered with it a bit did not do anything

[mockingbird]

Re: Dell Power Supply NPS-250KB B

The B20100's middle leg connects to ont of the legs of the 8 pin large ring coil. My guess is it has something to do with the +12V rail. Main switcher is a Fairchild FQA7N80C.

[Wester547]

Re: Dell Power Supply NPS-250KB B

Whoa... wait a second.... STPS2045CT x2 for the +12V rail!? That's 40A of current (28A in forward topology, but still)!!! Okay, forget the lack of output filtering, that's so overspec'd for the touted 14A (16A as of ATX12V 1.3) on the +12V rail... makes the single STPS20H100CT for the +12V rail on my out of commission Dell Hipro 250W look like nothing, though it had two 3300uF 16V Asiacon LEs and a PI filter for +12V filtering so it was far from lacking. What's the B20100 for? Is the main switcher a Toshiba part, IE 2SK2611? I also wonder if it's possible that one of the power outages did damage to one of the capacitors in the OP's PSU's voltage doubler.

[mockingbird]

Re: Dell Power Supply NPS-250KB B

Don't forget these come out of Dell systems that probably never went over 150W... Yes, two 200V 560uF Nichicon LU Primaries. I've got the UG10DCT for what I assume is -12V rectification, like yours, without the heatsink. All of my small caps are Taicon I think.

The other rectifiers on the secondary are:
STPS2045CT (2 of them one on each side)
L7912CV
STPS3045CW
B20100
MBR3045CT

[Wester547]

Re: Dell Power Supply NPS-250KB B

DNA1200E would be for secondary side overcurrent protection (I don't think that's causing the OP's problem, but you never know), etc. 1500uF + 470uF for the +12V rail... that's it? That seems really low coming from a PSU brand that knows how to make even underpar capacitors last ages. I have a Newton Power (NPS-250GB, Rev 01 B, datecode 0142) that also has a 470uF, 25V Rubycon YXG for -12V filtering (as well as L7912CV mounted to the other side of the heatsink and Panjit ER802 without a heatsink as its rectifier, I think), but all the other output capacitors are Ltec LZG and unfortunately the small capacitors are Ltec TK... voltage doubler has Nichicon LU though... it probably still works after 20,000 hours and 5,400 cycles of use because the Sunon sleeve bearing fan it has blows out a stunning amount of air and the heatsinks are very good and thick. It never really spits out hot or even warm air. It probably has the same configuration as yours (2200uF, 6.3V x2 for +3.3V and +5V, 2200uF + 470uF for +5VSB). Mine only has 3 optocouplers, though, and the only other PCB in the PSU is the input filtering PCB.

I find the 1500uF + 470uF configuration confusing because even older (albeit proprietary) Dell Newton 200W power supplies have more than that on the +12V rail, 2200uF, 16V Chemi-con LXJ + 330uF, 16V Rubycon YXF, though there's no PI filter or shunt to be found on that rail. Do you remember what the rectifiers were on the secondary side of the PSU, as well as the main switcher, if you checked? Also, I don't mean to derail this thread away from the OP's problem, so I'm suspect that either the 4th optocoupler is configured unfittingly or one of the small startup capacitors - a Ltec TK or Taicon VT - failed.