Dell Power Supply NPS-250KB B

[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

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

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

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

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

[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

[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.

[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.

[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.

[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?

[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.