overloaded PSU

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Hi all,

I just put together my Athlon 64 X2 5200+ system (overclocked to around
3Ghz) and it appears the load was more than my Wintech 350W could handle (as
it died very suddenly)..  It still supplies 5V standby, but it refuses to
turn on nomatter what..   The MB/CPU are up and running again with a spare
PSU.. but I underclocked it down to like 1.5Ghz so I didn't fry this one as
well..  (don't have a newer PSU so will need to order one).

I pulled the cover off and it gave off a weird smell, but it was only faint
and nothing appears burned..  (usually when a PSU goes there's remanents of
charcoaled components)..  Where should I start in diagnosing the problem ?
(and no I am not going to just throw it out)


Re: overloaded PSU

On Sun, 25 Mar 2007 02:27:23 -0500, "Skeleton Man"

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So how much work are you willing to do on a PSU that, once
repaired, may have the same limitation as before and other
weaknesses that can similarly cause failure?

How comfortable and competent are you to take readings of a
disassembled, live, partially high voltage (340V or so) PSU?
I'm not saying "don't" but to a certain extent,
troubleshooting it requires a fundamental knowledge of how
it works and along with that - the suspicions of what may
have failed - weaknesses, or parts subject to power line
surges, and how to go about checking it already.

Usual suspects include the switching transistors and
rectifiers, those are on both heatsinks.  Random failures
from other parts could be just that - random, anything
"could" fail, or could be due to poor design, poor layout,
cost-cutting, etc.  Each PSU will have to be considered if
the most common things aren't wrong, how to try to most time
effectively check the rest.

Consider that Fry's has sold Wintech made Ultra V 500W, and
(don't recall if it was Fry's in this case) 400W, for free
after rebate.  Radio Shack has also sold them for somewhere
between $10-20(?) after rebate.  If a new higher wattage
version is available (to be clear, I would much rather
have/use other brands of PSU, but for the purposes of this
topic...) for such low cost and no wear on it yet, how much
time is it worth to repair, and pay $ for parts (unless you
happened to have a bunch of replacement parts on hand, but
if they're decent, that is also a monetary investment in the
long run to maintain discrete parts stock), just to end up
with the same thing that failed already?

Perhaps we can try to counter this failure mode with an
improved replacement (discrete) part, or combat the cause if
environmental in some way (like fan RPM too low), but is the
result a PSU reliable enough you would deploy it, and if so,
how many times would you repair it before deeming it

Sorry for drifting a bit, to be comprehensive you would need
a scope, and alternate parts to plug in, and to pull a bunch
of parts to test them.  That's not always so easy with cheap
circuitboards that have thin copper reinforced by laying
down a wire on top of the copper or flooding the area with
solder.  Removing the solder and part(s) can start lifting
up the copper, and it can then require multiple additional
steps to rectify this as you have flux residue on the copper
and board requiring an extra step to get rid of, so your
glue or epoxy can adhere well to hold the copper down again,
so there's a wash cycle and drying time too.

From what I've seen of some Wintechs, they used a fairly
active soldering flux and didn't get a lot of it off.  Your
wash cycle needs to do this as getting it wet will make it
far more active and corrosive (to the PSU, it won't melt
your hand in any minor exposure).  Such minor little issues
become more and more significant on certain PSU - it is
usually best to take a close look at what you would
troubleshoot and repair before investing the time.  Maybe it
is a learning exercise or hobby and worth the time to you,
so I mention a few factors instead of that I would probably
throw it out or just pull the circuit board, crank up a heat
gun and shake the board, keeping any parts of value that
happened to fall out.  By keeping some of these parts
without excessive labor to do so, you have alternates for
testing/repairing other poor PSU so you don't incurr so high
a cost to maintain stock of parts as mentioned above.
Buying all individual parts to make such a poor PSU, it
would probably cost over $50 just to populate the circuit

After the visual examination of the top you might examine
the bottom of the circuit board as well.  Solder balls,
lifted traces, cold joints, may all manifest problems later
in life.  You may also see discoloration indicating thermal
stress on a part that led to it's failure.  It could be
something very minor like a 3.3V load resistor had ran hot,
pulled off the trace, and now PSU shuts down because that
rail isn't within proper voltage range due to the system not
putting a load on it.  We dont' have a description of any
basic voltage reading tests while it is hooked up to various
loads on 3V, 5V, 12V rails, only that it didn't turn on
(Hooked up to a system?).  If you are going to continually
troubleshoot and repair PSU, a bit of initial work to build
suitable minimal loads to plug a PSU into, keep it running
knowing all rails the manufacturer specs as *needing* a
load, have one, and more significant loads to simulate
moderate system... could be useful.

A schematic would also be useful, so you can better
visualize what parts of circuits should have what kinds of
voltage levels.  Otherwise you check what you can, trying to
trace back some of these oddly-routed and cramped budget PSU
can be headache inducing but if you can't find the problem
yet you will need to proceed *somewhere*, otherwise you end
up pulling off half the board components to check them.

Another alternative is to trace back the sensing rails on
the PSU - this I mean, is after checking other major things
like the transistors and diodes, and disconnect them from
their respective voltage/current sensing shutdown
subcircuits.  By disconnecting them, the faulty one, the PSU
may remain running still and you have found the subcircuit
to more carefully examine- either back through the supply
rail like that dual diode pack, or forward through the
sensing circuit (less likely to fail, but parts can and do
just fail for no obvious reason in some cases, you will have
to decide how important it really is to fix before taking a
fix-it-no-matter-how-long-it-takes, stance).  Obviously when
disconnecting these shutdown circuits, you don't want
anything of value hooked up as a load - so you use the minor
load jig/whatever you had set up for the purpose.

Also beware of multiple cascaded failure, one part shorting
puts more current into subsequent parts and it may be a
problem that kills more than just the first part that
failed.  You will have to examine the particular circuit to
see if it is a factor, I can't directly predict what a
super-budgetized PSU may have changed to cut production
costs.  If you are powering this PSU while testing, be sure
you do so safely.  A low current isolation transformer is
not a bad idea.

Other things you can try if you plan on doing this a lot is
building separate supplies to generate signals or voltage
levels you can "plug into" the problematic PSU to see if the
subcircuits you are troubleshooting, respond as
expected/required.  IE - if the PSU won't turn on to
generate the voltages, what if you put 5V on the sensing
line generated from another source- then you can see if the
zeners, transistors, etc are working, if the input at the
comparitor is as expected, and more.  For these you will
need spend a lot of time tracing and reverse engineering the
subcircuit if you don't have, I mean can't get, the
datasheets for the PWM controller chip or see a subcircuit
topology you recognize- and recognition will come after a
lot more attempts to repair, it is slow starting out if not
one of the more common failure points.

I seem to have drifted around a lot in this reply, a lot of
things are more straightforward when you have the PSU in
front of you and can just do it, rather than trying to
speculate without being able to rule anything out yet except
the most obvious things like that the fuse can't be blown
when it's still providing 5VSB.   For example you write that
nothing appears burnt but maybe with very strong light and
circuit board out, different angles, you might see something
on a component.

There are also some guides found by googling for various
applicable terms, for example "PC Power Supply Repair" turns
up this, http://www.nutsvolts.com/PDF_Files/PSRepair.pdf
Googling for ATX schematics will find some using the typical
TL494 controller yours probably uses, and while it may
differ from the schematics, a lot of it will be pretty
similar.  For example,
As expected you can to to TI's website and get a datasheet
for TL494,

I think I've already typed too much and haven't covered
everything so in closing I suggest Googling for each thing
you want to do if you don't know how - like checking BJT
transistors or diodes with a multimeter, or whatever, and
remember that a failed $10 PSU is not worth risking
electrocution or a jolt that sends your finger colliding
with a sharp metal edge or your whole arm against something
that causes harm.  Safety comes first.

Re: overloaded PSU

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If it's something I can accomplish with mininimal cost and labor I want to
do it as an exercise more than anything..  if it works I'll keep it as a
low-power spare.. (It wasn't meant for this kinda load anyway.. even the
mainboard/cpu info reccommends a minimum of 450W..

I have no problem taking measurements from a live supply..  a have two DMMs
(one has frequency, diode, transitor, and capacitance) and a small analogue
meter..  the only thing I don't have is a scope..  do they make handheld
versions of these like they do multimeters ? Also can you get LCD/digital
scopes as opposed to a CRO ?

Here's the breakdown of the specs (WIN-350PS):

+3.3V = 15A
+5V = 25A
+12V = 15A
-5V = 0.6A
-12V = 0.6A
+5VSB = 5A

Combined 3.3v/5v rails = 150W max

The voltages were all well within spec, I can't remember the exact figures,
but they were like +12.3V, +5.26V, +3.42v, etc.. (a hell of a lot better
than the readings from this temporary psu..  not a single one is within
spec..  all of them are 0.25 - 0.6v under par..)

The testing method to check if the PSU was dead is simple..  plug in an old
10GB HDD so there's some load and jumper PS-ON# to ground. I had it running
that way before.. but after it died there was no response..  it still sounds
like something charges though when I jumper PS-ON.. (like a very brief
buzzing noise)..

The psu came with my case about 3 years ago and I've never had a problem
with it til now, so I guess I got my money's worth..  I'll be putting a
brand name PSU in my PC next pay I think..  I was looking at the major
players like Silverstone, Enermax, Antec, Fortron, etc..  I'm thinking about
650W would be sufficient..

This is my current setup, maybe you can recommend a particular model PSU:

MSI K9N-SLI (nForce 500)
Athlon X2 64 5200+
2x 512MB Kingston HyperX PC6400 RAM
Radeon X1600 Pro 256MB
Western digital WD800JB
Western digital WD2000JB
Sony/Optiarc DVD-RW AD-5170A
AOpen CDRW CRW5232

You posted a lot of useful information, I'd be the last person to complain
about too much detail..  even if I don't go into that much detail to fix the
PSU, it's good to know incase I need to hack one up for a custom project..
On that note.. why do UPS's not just supply 5, 12 and 3V rails instead of
120V/240V ?  It makes very little sense to convert 12 or 24V from backup
batteries up to line voltage only to step it back down to 12V again anyway..

I've seen people hack up PSU's into DC-DC supplies that run from a car
battery, so the extra info helps..

Thanks kony..


Re: overloaded PSU

On Sun, 25 Mar 2007 14:59:16 -0500, "Skeleton Man"

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That's pretty much a made-up number they list then, it has
everything to do with what else is plugged into the system.
The board/CPU alone would run from a 200W mATX.  However, a
Wintech 350W may not be as fit to run a load long-term, as a
good 200W PSU would be.

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Yes, there are handheld w/LCD, you'd have to look at what's
available in your price range to see what sacrifices you'd
make.  Unless you really "need" it portable I suggest a
desktop model.  If nothing else it will keep it from being
dropped or stolen (so easily)  by staying on your bench.

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Ok but it's a Wintech, we can pretty much ignore those
numbers except to see that it may be more like a 250W PSU
than 350W, but one probably built as cheaply as possible in
some areas.

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5.26 is not within spec.  3.42 may not be either once the
ripple is accounted for.  IOW, if you had a reading of 3.42
but 100mV of ripple, it's out of spec, rising 50mV to 3.47.

Where are you reading these temps?  If not using the
multimeter, use it, not software.  

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... would be overkill unless you're running SLI'd video
cards.  You are contrasting low-end, came-with-case PSU with
one that's more than you need.  Just get a median wattage,
well made PSU.  Your system will be fine with any decent
400W, maybe jumping to 450-500 just to cover some extra
current from overclocking.  That it was running from a 350W
Wintech is in itself evidence it would run fine from a good
350W PSU (instead of the Wintech).

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There are a lot of PSU that could run that, I suggest you
assemble a list of brands you would consider then buy
whichever goes on sale first... it's not like there's enough
difference to matter in reasonable quality PSU.  The main
thing is to avoid the junk out there.  A name-brand $50 PSU
is much closer to what you need than a repaired, generic

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Batteries start above 13V and drop below 12V, they have to
be re-regulated anyway for good results.  You could build a
custom UPS for one system, but it would be too great an
expense for the limited market segment which has a similar
enough system to use it.

You can buy PSU that run from 12V input, if that's what you
want, don't get an UPS... get a battery charger, battery and
12V input PSU.  By making a traditional UPS as 120V output
it is the most compatible thing possible... and really, what
do they care if you have to pay them more for a larger UPS
to get the job done?

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It can be done, but to do it well it may be a lot more work
than it's worth since there are ready-made 12V input PSU,
now even purpose-built to be used on a car PC.

Re: overloaded PSU

Skeleton Man wrote:

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An AT PSU repair guide.  It applies to AT PSUs but should still be
useful for ATX PSUs:


Lots of switching PSU repair information from the RepairFAQ.org,
edited by Sam Goldwasser:


I'm no expert, but I find that ATX PSUs are so crowded inside that
it's very difficult to take measurements without removing the circuit
board from the case for access to the bottom of the big circuit
board.  BTW, don't touch the big heatsink containing the high voltage
components because many 170VDC on them.  I don't think that Wintech's
do, but I've measured 170V on Delta, Enermax, and Antec (Channel Well
mfg.) heatsinks.

I'd rather work on the PSU with the AC cord unplugged and the big
capacitors discharged and measure the fuses, transistors, and diodes
with an ohmmeter or diode checker.  You may have to remove them to
gain access, and often the easiest way to by unsoldering all of them
and lifting out the whole heatsink.

Re: overloaded PSU

Well I now have a supspect component.. part number LT334D (3 pin transistor
casing), which I'm guessing is a rectifier.. it's attached to a heatsink and
all 3 pins measure as a dead short..   I must need a bigger iron to remove
it though, as my 25W pencil iron won't do it.. (the heatsink absorbs all the
heat when I try to unsolder it)..

I'm guessing the heatsink is live too, because there's no washer between the
part and the heatsink..

If I could get it out I could test it better.. any suggestions are welcome..


Re: overloaded PSU

Skeleton Man wrote:

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The parts in my 350W Ultra/Wintech with numbers starting with "LT" are
dual Schottky diode packs and are mounted on the low voltage
heatsink.  I can't find information for your particular part, but look
for something that at least meets the amp ratings for its particular
voltage rail (some parts are rated for amps per diode, so double this
rating).  Also some PSUs use these diodes in parallel pairs for some
voltage rails, on opposite sides of the heatsink, and if one is
defective, replace both, using components with part numbers identical
to one another so that they share the current equally.   My Wintech
has two empty spaces for such extra diodes.   If you can't find the
right diodes locally, either try Mouser.com or rip them out of junked
PSUs, even ancient AT models (it's amazing how <200W AT PSUs contain
parts with the same ratings as newer 400-500W PSUs do).

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Some component packages are designed with built-in insulation, but
check any replacement's because it may insulate only the mounting
screw (still need insulator sheet) or insulate nothing at all (need
insulator sheet plus nylon shoulder washer -- don't substitute regular
flat nylon washer).  If your insulator sheet is silicone rubber, it's
not absolutely necessary to smear thermal paste on it, but transparent
sheets need it on both sides.  Also be sure the paste is
nonconductive, i.e., contains no silver.

I use a 35-40W soldering iron on single-layer circuit boards, and it's
a necessity for the tabs attached to the heatsink.

Re: overloaded PSU

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That sounds about right for mine... this one is like in the middle of the
low voltage side right infront of a transformer..  (there are a few mounted
next to each other further back, but those appear to be ok).  The diagram on
the package looks like this:  ---->|---|<---- (two diodies pointing toward
each other).

My biggest challenge is going to unsoldering the heatsink I think..  too
many components in the way to unscrew the part from the heatsink and remove


Re: overloaded PSU

Skeleton Man wrote:
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Consider a propane torch.  I kid you not.

Chuck F (cbfalconer at maineline dot net)
   Available for consulting/temporary embedded and systems.

Posted via a free Usenet account from http://www.teranews.com

Re: overloaded PSU

On Thu, 29 Mar 2007 19:27:32 -0500, CBFalconer

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I agree, have used one myself though it is a small
pencil-sized torch.  Main thing about using one is you have
to be a bit practiced at it to get a feel for how far away
and how long to apply the heat to get the solder melted
without burning the board.   Thus it would be good to
practice the technique on something worthless.

Another issue is that some of these (cheaper PSU,
especially) may have thin copper that is beefed up by being
flooded with solder.  A lot of solder that can be a pain to
manage when heating a larger area.

The Wintech PCBs I've seen had fairly generous (overly
large) holes and are single-sided (copper), they also do
fairly well with a typical solder-sucker to clean around
each pin of the components, then either desoldering wick to
remove, or a probe to push the pin away from, what little
solder remains around it.  It still requires what the OP
lacked, a more robust soldering iron.  Personally I would
focus on getting such an iron before I'd put money into
repairing a generic PSU, as the iron is far more useful and

Re: overloaded PSU

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A torch is on my list of tools to buy..  I wanted one for another purpose
anyway, so if I can solder PCBs/components with a flame it's even better..
(do I use the flame itself or buy a metal tip for the end of it like an
electric iron ??)

I've seen some that use triple distilled butane or something.. are they any
better than your average pencil torch that uses regular butane ? For that
matter is there a lot of difference between propane (disposable cyenders
with a torch screwed onto the top) and butane torches ?


Re: overloaded PSU

On Fri, 30 Mar 2007 12:40:46 -0400, "Skeleton Man"

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Actually using a torch is a last resort, because it does not
allow fine control of the amount of heat applied.  It is
do-able with practice, but the potential to overheat parts
is far higher than any other method.  Most of the time I use
a torch it is just to guerrilla-cannibalize something dead,
to spend the least time possible to get a lot of parts off
for salvage purposes.  In that case if the PCB is scorched
or a part overheated, I don't care as no one part was
critical to salvage, they all just get dumped into a jar
where there are plenty of spares of any given part.

The better tool for this kind of larger area work is a heat
gun.  By being able to set the temp, you then have a set
upper limit on how hot anything could get, a larger margin
to work with, and it is far less likely to damage parts,
lift traces, burn the board, or the coating on it.

In general these things are supplimental tools, the basic
requirement still stands to have a higher wattage soldering
iron and basic desoldering tools like the vacuum sucker, and
desoldering wick/braid.

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Butane is a lot handier, to have a small cylinder to refill
a pencil torch.  I feel you are on the wrong track though,
the torch is only the reasonable option if it's all you had,
already on-hand and had enougn practice to control the heat.
I would not recommend buying one before having a
temp-adjustable soldering station.  It is far more useful
and safer.  That plus the vacuum pump and braid are all that
is required to do the repair well if you had a hotter iron.
With the torch there is not only the danger of overheating
and getting excess solder elsewhere, that solder still has
to be removed and the new part soldered on satisfactorily...
which is harder with a torch because the torch temp being
harder to control, will tend to burn up flux too fast
leaving residue that impedes solder flow, as well as using
up the flux meant to make the solder flow better.

Maybe I'm being too picky, it's not at all impossible to use
a torch, but it isn't the best tool for the job and if
you're the type of person who is repairing stuff like this,
it seems inevitable you will need a stronger temp-controlled
soldering iron/station, and will be making things harder on
yourself until you have one.  If what you presently have is
one of those crude Radio Shack types of irons with the long
nickle plated threaded tips, just upgrade it and don't look
back, those are too much of a PITA for anything but very
easy medium-small sized jobs only.

I can't see exactly what you're dealing with but here are a
few lower cost suggestions.


(you will need a heftier tip to do such work, perhaps:)
(or you may find compatible tips (Hakko 900M series for
example) for less on ebay, or elsewhere).


I don't know if this iron gets hot enough, but if it does it
would need a compatible (not the one linked above) heftier
tip).  Regardless it is a reasonable deal as the pump alone
is often $5 or more.  For general purpose uses the iron
might do fine but for these large parts/areas on a PSU, you
might just want to ignore that link, I almost didn't link it
at all as you'd much better off with a more powerful
solering station, or at least a higher wattage iron like

but even this one, I can't tell if any of the included tips
are adequate... a 50W iron with a tiny pencil tip won't be
any better than a 30W would with a hefty chisel tip,
particularly when it comes to heating up desoldering braid
to soak up excess solder.

The other benefit to a soldering station is that at it's
regular running temp, it has reserve power... just putting
the tip to the circuit board, the tip starts to cool causing
the station to apply more power to the element to keep it at
the desired temp.  Being able to keep the desired temp
instead of trying to use something too hot, within an
assumption that (too hot) thing would be cooled to a safe
level while heating up the area, makes the difference
between a torch and the ideal tool.  With a torch you can
vary the gas some, but mostly you have to back it away from
the job, which heats an ever larger area than you wanted,
and on a PSU, can even make some of the other parts fall out

MPJA may have more deals at the moment but Circuit
Specialists also has flux... always nice to have some,
especially for work where there is excess solder, it helps a
lot getting the excess into the desolding wick and to be
able to reflow the existing solder when the new part is
installed, instead of trying to add more solder just to get
some flux out of it when there was already enough (or nearly
so) solder, just not enough flux.

Circuit Specialists also has some other related items I've
not linked, like a station equivalent to the one at MPJA,
 and one slightly better for only $5 more,
but it doesn't have a removable wand which is less handy (I
like having two wands each with a different tip so waiting
for irons to cool or switching tips is eliminated, you can
go even further by buying two stations but two irons might
be close enough in convenience as these stations only take
about 30 seconds to get up to typical temps).

Naturally you can spend more and get more, up to a point.
Hakko is a very popular brand for an entry level station,
but it mostly the same as the above linked ones.  On
Circuitspecialists site above there are also hot air
stations, but price goes up rapidly, these are typically
$100 at least, quickly climbing in price.  IMO, overkill
unless you do quite a bit of soldering/desoldering work, and
no replacement for a better iron than you have... so
essentially a better soldering iron, vacuum pump and
braid/wick would be my recommendation.  The pump need not
have integrated iron, I find that quicker and easier but
there are plenty of separate pumps, both of the two above
'sites should have some.  Circuit Specialists also has a
continual promo where you get a free multimeter or tools
with a code on their promo page if you buy $50 worth of
stuff, but their shipping charge is higher than average,
while MPJA's is lower than average... it'd cost about $8
more to ship an equivalent order from Circuit Specialists
than MPJA in most cases.  

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