Dell L350N-00 350W PSU issue.

[stevo1210]

I have a Dell L350N-00 24 Pin 350W PSU here on my bench and for some reason its recently gone haywire.
I previously had this PSU powering an Intel P4 Northwood Celeron system that was my fathers media center. About a week ago I put this PSU into my brothers P4 Prescott system with an Intel DP965LTCK motherboard and his PC is loaded with a lot of peripherals compared to the media center PC.
His PC wouldn't stop bootlooping and doing random shutdowns. It turned out to be a power problem and I got him a new PSU and all is fine now. My theory was that the PSU didn't have enough wattage.
I put this PSU back into the media center system that it was previously powering for months without a problem and the media center system also bootloops.
I popped open the case of the PSU and found no badcaps and there was nothing burnt.
What I have noticed is that the voltages on the 12V rail fluctuate so much that it is unbeilievable. It was going from 11.163V and up to 12.2V continuosly from what I could see in the Asus PC probe program.
Does anyone know what could be wrong with my PSU?? ANy advice would be good.
I don't want to scrap the PSU because it is a decent unit compared to the DEERs. L&Cs and Raidmax ones I have waiting in my junk box.

I have some images of the actual PSU in this thread: https://www.badcaps.net/forum/showthread.php?t=4929

EDIT: I've also taken notice that if I power the PSU off (unplug) for over a night and power it back up in the morning my PC will work for hours without any issues. But If I put the system into soft-off and boot it back up after let's say an hour, the system immediately shuts off at POST. I then have to leave the PSU unplugged overnight and start it up again in the morning to get some use out of it.

Thanks.

[stevo1210]

Re: Dell L350N-00 350W PSU issue.

Oh I forgot something. When this PSU was powering the Prescott system my brother has, we could hear something like a small clicking noise that was continually emitted from the PSU. When it was put back into the media center system, the clicking noises disappeared but now even my media center bootloops and shuts down ??!!.
Oh, and even the replacement PSU for my brothers system has less wattage than this PSU. His new PSU is also a Lite-on one and it is only 300W compared to the 350W this one is supposed to pump out....

Thanks.

[starfury1]

Re: Dell L350N-00 350W PSU issue.

oh Stevo now thats a worry.......

we did have a thread going on a similar situation to this
(wasn't to do with you from memory)

But there is one circuit that runs 24/7 will the psu is plugged and "switched" ON

Thats is the + 5 Volts Sand By circuit

I do also vaguely remember it was mention (I think by Rainbow or gonzo) that regulation of 12 V is tied to 5V so (not sure if that was 5VSB thought???)
with some of the older psu's

so thats probably were to start looking

Don't know where the thread is off hand and would have to have look at psu to try and identity were to start looking but chances are you may have issues with that

Another possibility I sort of remember is possibly power resistors bad joints.

It appears that when the thing is cold everything is good but something that is warm is flaky
Fair chance it might be lower value caps around those circuits
(like 1~100 uf 25v 50v jobs...)

it could be caps but other things are possible (and possibly more likely)

that is about the best I can do at the moment
maybe someone will know whats most likely to have failed with that model

Hope this is of some help anyway

Cheers mate if I find the thread I'll post a link


Clicking noise no idea but I do remember you mentioning it a long time ago

[starfury1]

Re: Dell L350N-00 350W PSU issue.

Has Liteon PS-6351-1D?... whatever on the PCB

maybe that will help

[kc8adu]

Re: Dell L350N-00 350W PSU issue.

had a dell liteon come in here with the +12 at 10.1v
scope showed 5v p-p of trash.open teapo 2200@16
it got a total recap.
the box it was in had intermittant no post and hdd spindown/clicking.

[starfury1]

Re: Dell L350N-00 350W PSU issue.

Think he part recapped that one ....
but yeah recheck your work stevo if you did
(wont hurt and sometimes it does come back to what you did...of cause you rule it out so go chasing your tail somewhere else till eventually you are back at what you did as the problem...does happen )

Are they Hitano low ESR you used?? I know you got some at some point
EXR (I think) was the series...
not the best cap for the job but still think it should have done better then a few months.

Anyway it wouldn't be the first time a component died before time so I'd just replace it to rule it out.

then if that dont fix it "let the chase begin...."

Cheers ...thanks Kc8

[stevo1210]

Re: Dell L350N-00 350W PSU issue.

Think he part recapped that one ....
but yeah recheck your work stevo if you did
(wont hurt and sometimes it does come back to what you did...of cause you rule it out so go chasing your tail somewhere else till eventually you are back at what you did as the problem...does happen )

Are they Hitano low ESR you used?? I know you got some at some point
EXR (I think) was the series...
not the best cap for the job but still think it should have done better then a few months.

Anyway it wouldn't be the first time a component died before time so I'd just replace it to rule it out.

then if that dont fix it "let the chase begin...."

Cheers ...thanks Kc8

I haven't actually recapped this PSU yet. It's in original factory condition. But I have recapped another Dell/ Hipro PSU before with Hitano EXR series caps. I have also recapped my DEER PSU with Hitano EXR caps to power some PII and PIII systems.
All the caps in this Lite-on unit are OST and Ltec (With the exception of two Elite brand primaries) and none of them seem to be bulging or leaking. But I will have to somehow check to see if the caps are open. I don't have an ESR meter here.... is there any other way?? like using a digital multimeter??

Thanks.

[starfury1]

Re: Dell L350N-00 350W PSU issue.

Well if it hasn't been recapped in its life the simple way mate is just recap it...
given the age of it and it has issues
its probably simple best solution.

The caps looked black and Gold to me so thats why I asked

you could just try the one pointed out by KC8 for a start and see if it settles down and behaves, at lest then you will know thats the issue.
but a total recap will not hurt, as you well know.

The having to unplug it may well be another issue.

Id try KC8 solution first then see what happens....a full recap is in order thought if you going to keep it and don't want issues further down the track.

Cheers keep us posted