PSU to MoBo ATX 20 pin power connector

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

Threaded View
Due to a continual poor connection on one of the ATX pins I am considering
hard wiring, soldering, the 19 wires direct to the MoBo.

any recommendation/practices that must be considered.

other than make sure the comp is off :-)


Re: PSU to MoBo ATX 20 pin power connector

Quoted text here. Click to load it

When the contact quality drops on two mating power connectors,
the solution is to replace both connectors. Replacing just
one connector (i.e. using another power supply) won't fix it,
and the bad pin will start to fail again. I would not recommend
soldering wires directly to the board, because the power supply
might fail, and that would require removing the wires and
repeating the repair (and you'll only want to do this
repair once - trust me). In any case, the unsoldering of the
old connector is the hard part.

From one of the specs for power supplies:

  "ATX Main Power Connector
   Connector: MOLEX 39-01-2200 or equivalent
   Mating motherboard connector is Molex 39-29-9202 or equivalent"

Molex document for 39-29-9202 motherboard connector:

(Couple models for sale here - down near the lower right corner)

You are going to hate the unsoldering job. How easy that
connector would be to remove, depends on how tightly the
pins fit the holes, and how much heat you can get on the
work. Practice on something dead first. A vacuum desoldering
station would help a lot for this. A manual solder sucker will
also work (the pump action kind), but you'll probably have to
clean it several times before you are done. If there was some
way to remove the nylon part of the connector, this job would
be _so_ much easier. I keep a cheap 80W uncontrolled iron for
stuff like this, and would not expect a 35W uncontrolled
iron to be hot enough. I'm not rich enough to afford a
solder station with controlled temperature tip.

The best solution, is find somebody else to do it :-) With
a couple of spare new connectors in hand, approach a
radio/TV repair shop, and see what they would charge for
the work.


Re: PSU to MoBo ATX 20 pin power connector

WTF wrote:

Quoted text here. Click to load it

Practice your desoldering skills on an unneeded 4-6 layer PC board
since they require much more heat than 1-2 layer boards.  An iron (not
gun, not torch) capable of putting out a maximum of 50W is desirable,
but a 40W iron can do the job if its tip is kept clean and is chisel
shaped and you pause 15-30 seconds between pins to let the tip heat up.
 Desoldering can be done with solder suction bulbs or plungers, but
copper desoldering braid, kept trim to reduce heat dissipation, is
safer for the board..

Unless your ATX pins are burned and corroded, there's no reason they
can't deliver adequate current to your motherboard with virtually no
voltage drop.  Loose pins can be bent back tight with a dental pick or
jeweler's screwdriver.

Re: PSU to MoBo ATX 20 pin power connector

On 13 Mar 2006 16:08:22 -0800,

Quoted text here. Click to load it

The heat difference is fairly trivial.   Heat is a function
of connected metal and/or thickness- they aren't necessarily
any thicker and they don't have multiple layers connected,
those other layers are ONLY for other purposes, what good
would it do to have all 4 layers connected to the power
supply pins?

However, it will require significant heat merely because it
is a high-current power plane or very thick trace.

Re: PSU to MoBo ATX 20 pin power connector

kony wrote:
Quoted text here. Click to load it

That's true for signal traces, but anything that connects to a ground
or power plane needs about twice as much power to desolder.  Would you
ever willingly desolder a motherboard power connector with just a
25-30W iron?

Re: PSU to MoBo ATX 20 pin power connector

On 14 Mar 2006 17:06:39 -0800,

Quoted text here. Click to load it

Of course a 25W iron isn't enough for this, and yes a power
or ground plane is one of the worst areas (the worst two) to
desolder.  On the other hand, they are still 1-plane
connections to the pin, if the board had simply been
manufacturered without the other non-contact planes on the
board, it wouldn't be any easier to solder.  Multiple planes
doesn't increase heat needed except in limited circumstances
where having the multiple planes meant the plane was more
continuous because the multi-layer design meant it wasn't
constrained as much by available space.  In general, having
the sufficent 40+W iron one can ignore the issue of it being

Re: PSU to MoBo ATX 20 pin power connector

A lot of things to consider.

The size of the Tip, the heat of the tip, the size of the solder joint, how
many layers, the dwell time needed (optinum 2-3 seconds) the type of solder
(tin/lead ratio) leaded or leadfree, oxidation at the joint, flux to be
used, etc.

If you are reading these for the first time then I suggest you pass on the

If the connector is not seating tightly to the header then replace the
connector at the PS end.

Quoted text here. Click to load it

Re: PSU to MoBo ATX 20 pin power connector

On Mon, 13 Mar 2006 18:57:33 +0000 (UTC), "WTF"

Quoted text here. Click to load it

Why is it poor, this is important to determine.
Was the current too high or was one or both connector
contacts malformed?

There is no need to hard-wire 19 wires.  Replace the one pin
in the motherboard socket... heating it up enough to come
out, it'll pull all the way out.  It might be hard to do the
first time, if you have an old junk board it would help to
practice on it.

As for the motherboard connector, slip the wire out and put
a new connector on it as well.  If you can't find the
connectors or it would be cost-prohibitive to buy just a few
instead of hundreds or thousands of them, take the connector
out of another old/dead/whatever PSU, leaving it on the wire
and grafting the connector w/lead onto the original PSU
wire, keeping in mind that if the problem was high current,
you need make sure the mechanical plus solder connection of
the two wires is sound.

Which PSU connection is this?

Quoted text here. Click to load it

Use a very hot (high wattage) iron.  Don't bother trying to
desolder the whole connector, just use the destroy-the-part
method of removing it.  IE- Grasp each pin in needle-nose
pliers (personally I find locking forceps good for this type
of thing), heat the back of the pin and be pulling on it
lightly.  You will need a support to keep the board upright
to do it easier.

When the solder melts, the pin is already hot enough to have
began melting the plastic connector as well so as soon as
you feel it pulling out a little with the forceps, pull
harder with the solder melted and it just comes right out,
easily.  If it's not coming out easily, you probably dont'
have a high enough wattage iron or poor iron-pin contact to
transfer heat.  Another poster suggested a 40W iron- it
would work with a good tip, using proper procedures, but
might be easier with a pistol grip 100W iron.  Because there
is so much copper near the pins, the lower the iron wattage,
the more heat is lost along the copper before the solder
melts.  Mainly, if you use the hotter wattage iron you
should be sure not to overheat either, pulling the pin out
immediately after the solder has melted... you have about a
0.5-1 second window of opportunity which seems short but
once you get the hang of it, is like clockwork.

Anyway, you might pull the bad pin out first and see if you
can replace it.  The solder, since it wasn't sucked up or
wicked away with braid, may close in around the hole a
little but a ~ 1/32 drill bit should open it back up if used
carefully.  Even if you want to use a pump or wick to remove
the excess solder (on all the pins), it may be much easier
to pull the pins out first than to try and wick away enough
solder to cold-pull out a (then) loose connector from the
typical plated hole motherboard.

Site Timeline