On Fri, 30 Mar 2007 12:40:46 -0400, "Skeleton Man"
<invalid@guestwho.com> wrote:

>>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
>>long-lived.
>
>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 ??)

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.



>
>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 ?

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.

http://www.mpja.com/directview.asp?product=16922+TL

http://www.mpja.com/directview.asp?product=15140
(you will need a heftier tip to do such work, perhaps:)
http://www.mpja.com/directview.asp?product=15150
(or you may find compatible tips (Hakko 900M series for
example) for less on ebay, or elsewhere).

http://www.mpja.com/directview.asp?product=2648

http://www.mpja.com/directview.asp?product=16431
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
this,

http://www.circuitspecialists.com/prod.itml/icOid/8132
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
unintentionally.

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.
http://www.circuitspecialists.com/prod.itml/icOid/2555

Circuit Specialists also has some other related items I've
not linked, like a station equivalent to the one at MPJA,
http://www.circuitspecialists.com/prod.itml/icOid/7307
and one slightly better for only $5 more,
http://www.circuitspecialists.com/prod.itml/icOid/7501
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.