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Desoldering question (Miller XMT welder repair)

B

Bill

Jan 1, 1970
0
everything. I took this welder out of its protective shell, vacuumed
it, and then blew the dust out using compressed air (outdoors). The
truly amazing thing, is that it was still functioning fine with all
that dust inside.
<snip>

NOooooooooo, you blew away all of the magic dust!!!! Now it will surely
self destruct when you need it the most. Never blow away the magic dust,
it annoys the tool gods.. ;)

Bill
 
J

James Sweet

Jan 1, 1970
0
Having said that, I would like to apply that coating to the areas that
I re-soldered. What is that coating?


You can buy cans of conformal coating at a good electronics shop. Vetco near
me carries it, I'm sure you can find it online as well.
 
D

Dave Plowman (News)

Jan 1, 1970
0
I have several solder suckers. In close quarters sometimes solder wick
does the trick, and it always works. I've got one of those big blue
nasty things, and a couple of smaller aluminum solder suckers. In
close quarters I still find myself reach for the solder wick.

A solder sucker ain't the same as a desolder station. Of course solder
wick is useful but the desolder station works for pretty well everything
here. But probably too large an investment for occasional use.
 
J

James Sweet

Jan 1, 1970
0
A solder sucker ain't the same as a desolder station. Of course solder
wick is useful but the desolder station works for pretty well everything
here. But probably too large an investment for occasional use.


A good compromise are those suction bulb desoldering irons, I've used one
for probably 15 years now. I never had any luck at all with the separate
solder suckers, it's too hard to apply heat and suction at the same time. I
keep wick around too, neither is a one size fits all solution.
 
D

Dave Plowman (News)

Jan 1, 1970
0
A good compromise are those suction bulb desoldering irons, I've used
one for probably 15 years now. I never had any luck at all with the
separate solder suckers, it's too hard to apply heat and suction at the
same time. I keep wick around too, neither is a one size fits all
solution.

Snag with both of those is two hands needed - which usually means rigidly
mounting the work piece.
 
J

James Sweet

Jan 1, 1970
0
Snag with both of those is two hands needed - which usually means rigidly
mounting the work piece.



Not with the suction bulb desoldering iron, I'm not sure how you'd use it
two handed if you wanted to..
 
D

Dave Plowman (News)

Jan 1, 1970
0
Not with the suction bulb desoldering iron, I'm not sure how you'd use
it two handed if you wanted to..

I've not used one but I'd have thought trying to hold it steady on the
joint while operating the bulb with one hand might be a tad tricky?
 
J

James Sweet

Jan 1, 1970
0
Dave Plowman (News) said:
I've not used one but I'd have thought trying to hold it steady on the
joint while operating the bulb with one hand might be a tad tricky?


Not at all, you hold it in your hand with your thumb on the bulb, it's
really easy to use. I'd rather have a vacuum operated desoldering station
but this fits in my toolbox. Only real trick is to keep a fresh tip on it,
when they wear out they don't get a good seal.

http://projects.jheiv.com/images/blog/2006-03-20/03-18 Desoldering Iron.jpg
 
K

Ken G.

Jan 1, 1970
0
I cant help but ask why dont you take the solder sucker device apart and
check out the problem ?

You were able to repair the welder .
 
R

Ross Herbert

Jan 1, 1970
0
On Wed, 30 Jan 2008 09:34:29 -0600, Ignoramus19508

:>
:> Your desoldering tool (like most) is probably fitted with a small diameter
tip
:> (approx 0.8mm - 1.00mm inside diameter)
:
:Yes.
:
:> designed for sucking solder from around small gauge component leads
:> and IC pins where the tip make full peripheral contact with the
:> board. When the solder melts around a pin all the air passes solely
:> around the lead and maximum effect is achieved inside the through
:> hole.
:
:Well, it does this pretty well with a real vacuum pump attached
:instead of the "desoldering station pump".

Yes, of course it will. But the desoldering station pump is NOT a specialised
1/3HP vacuum pump. It is designed as being adequate to suck solder from around
component pins ONLY when the nozzle completely surrounds the lead AND make 100%
peripheral contact with the pcb solder pad.
 
A

Arfa Daily

Jan 1, 1970
0
Ross Herbert said:
On Wed, 30 Jan 2008 09:34:29 -0600, Ignoramus19508

:>
:> Your desoldering tool (like most) is probably fitted with a small
diameter
tip
:> (approx 0.8mm - 1.00mm inside diameter)
:
:Yes.
:
:> designed for sucking solder from around small gauge component leads
:> and IC pins where the tip make full peripheral contact with the
:> board. When the solder melts around a pin all the air passes solely
:> around the lead and maximum effect is achieved inside the through
:> hole.
:
:Well, it does this pretty well with a real vacuum pump attached
:instead of the "desoldering station pump".

Yes, of course it will. But the desoldering station pump is NOT a
specialised
1/3HP vacuum pump. It is designed as being adequate to suck solder from
around
component pins ONLY when the nozzle completely surrounds the lead AND make
100%
peripheral contact with the pcb solder pad.

Well Ross, I gotta tell you that I use my Weller desoldering station just
about every day, I keep the same sized tip on it with a 1mm hole at all
times. It is used both for pin sizes where the hole will fit over the pin,
as you describe, and also for any other joint that I need to get the solder
off as well. I have never had a problem with it developing enough suck to
remove solder from a joint that requires the tip to be applied in a way less
than your stated 'ideal', unless it has reached the point where it needs
servicing. I think that in common with most soldering / desoldering tools,
it depends on how often you use it, and hence how much skill in its use,
that you have developed.

Arfa
 
A

Arfa Daily

Jan 1, 1970
0
Bill said:
<snip>

NOooooooooo, you blew away all of the magic dust!!!! Now it will surely
self destruct when you need it the most. Never blow away the magic dust,
it annoys the tool gods.. ;)

Bill

Oh Boy ! Now he's REALLY in trouble ... Does he not realise that the magic
smoke is kept in by this thick layer of magic dust ????

Arfa
 
P

Pete C.

Jan 1, 1970
0
Bob said:
I have several solder suckers. In close quarters sometimes solder wick does
the trick, and it always works. I've got one of those big blue nasty
things, and a couple of smaller aluminum solder suckers. In close quarters
I still find myself reach for the solder wick.

None of those little solder suckers compare to a real properly
functioning desoldering station. When I spent a summer working at a
fiends stereo repair shop we had the Hako deoldering stations and I
could desolder blown output modules faster than you could even uncoil
your solder wick.
 
D

Dave Martindale

Jan 1, 1970
0
Ed Huntress said:
The solder in a joint can wind up having a much higher melting point and
much less wetting ability than it did when it was initially applied. That's
because it amalgamates to the material being soldered to some degree. If the
joint was the least bit overheated initially, or upon re-heating for
removal, it can be a fairly high degree.
You notice it more trying to unsweat copper plumbing. Sometimes you have to
wet the joint with some fresh solder to get it to come apart. But I've run
into the same thing taking components off of an old board.

I've also noticed that I often need to add solder to make a second try
at unsoldering a component lead if the solder sucker didn't get
everything on the first try. I theorize (but can't prove) that the
extra solder is sometimes necessary to carry heat all the way down into
the plated-through hole, to melt the solder all the way through the
hole.

If the component that's being removed has nice fat copper leads, those
can carry heat pretty well (assuming you can make good enough contact
between the iron tip and the lead). But IC leads don't seem to be
terribly good heat conductors. A nice bit of liquid solder does a
better job of conducting heat from the iron tip down into the PCB hole.

Dave
 
J

James Sweet

Jan 1, 1970
0
None of those little solder suckers compare to a real properly
functioning desoldering station. When I spent a summer working at a
fiends stereo repair shop we had the Hako deoldering stations and I
could desolder blown output modules faster than you could even uncoil
your solder wick.



I don't think anyone who's used one can argue against it being the superior
choice, but wick and other methods have their place, they fit comfortably in
a small portable toolbox.
 
I

Ignoramus19508

Jan 1, 1970
0
Just a little update. I found a certain adjustment that I adjusted
and the vacuum increased very substantially. I think that this station
is perfectly usable now as it is.

i
 
E

Ed Huntress

Jan 1, 1970
0
Dave Martindale said:
I've also noticed that I often need to add solder to make a second try
at unsoldering a component lead if the solder sucker didn't get
everything on the first try. I theorize (but can't prove) that the
extra solder is sometimes necessary to carry heat all the way down into
the plated-through hole, to melt the solder all the way through the
hole.

If the component that's being removed has nice fat copper leads, those
can carry heat pretty well (assuming you can make good enough contact
between the iron tip and the lead). But IC leads don't seem to be
terribly good heat conductors. A nice bit of liquid solder does a
better job of conducting heat from the iron tip down into the PCB hole.

That's probably true, but there's also a lot of amalgamation going on.
That's why copper soldering iron tips get pitted from solder; it amalgamates
with the copper. Notice that the pasty glop on a soldering iron that isn't
continuously re-tinned (or that has an iron-plated tip) has a higher melting
temp. When you wipe the glop off and re-tin, it runs a lot easier. The same
is true in a soldered joint.
 
J

Jon Elson

Jan 1, 1970
0
Ignoramus1782 said:
I just finished a mini project. I fixed a "broken" Miller XMT 300
CC/CV welding machine, which had the switch for the display
broken. That switch was switching the display between showing voltage
or current on a mini LED screen.

The broken switch had to be desoldered and a new one had to be
soldered in.

The issue that I ran into was desoldering. I have a "Pace SMD 2000
desoldering station" from my younger military surplus days. This
station has a tool that is like a soldering iron, but has a axial hole
in the tip and an adapter for a vacuum, and the built in vacuum. When
I push on a pedal, the vacuum starts sucking through the tip. So I
would melt the solder with the hot tip, push the pedal and...

My problem was that it barely sucked. Not enough to vacuum in the solder
from the circuit board.
You say "built in", that has the diaphragm pump in the power
supply box, or a Ped-a-Vac venturi vacuum generator that runs
off compressed air? Either way, there are likely disc-type
filters in the line that become clogged with flux residue.
The old ones had filters that you could pop open and replace the
elements in, the new ones are "non-repairable". But, I found
you can drip rubbing alcohol through the hole, let it sit a
while and repeat a couple times, allowing the alcohol to drip
out onto a paper towel. When the drips come out clean without
staining the towel, the filter is magically rejuvenated.
(Note the box may have ANOTHER disc filter hidden inside, it may
also be dirty.)

Second, there is a wad of felt in the glass tube inside the
handpiece that also becomes saturated with fine solder dust and
flux. I have not found those to be recoverable due to the
non-soluble dust. I got a bag of them with the machine, so I'm
probably set for life.

Third, the hole in the desolder tip fills with oxidized solder.
I have to rod the hole out every half hour or so when using one
a lot. I just use some handy solid wire and jam it in, twist it
around and pull it out, suddenly the "Suck" is audibly stronger.
As a stopgap measure, I used my 1/3 HP vacuum pump by connecting it to
the desoldering tool and turning on at the proper moment.

In the end, it all worked, the old switch was removed, a new one
installed, and the welder has a working selector of V vs. A display.

All this leads me to the conclusion that something is wrong with the
vacuum pump on this station. Would you say that it should provide very
strong suction?
I'll bet your filters are clogged. I have a motorized one at
work and a compressed air one at home. Whenever I hav a
problem, it is the filters or the tip.

Jon
 
J

Jon Elson

Jan 1, 1970
0
Ignoramus19508 said:
Just a little update. I found a certain adjustment that I adjusted
and the vacuum increased very substantially. I think that this station
is perfectly usable now as it is.

i

This is the knob that throttles the OUTPUT pressure? Yeah, it
chokes off the outlet of the pump, thereby killing its vacuum
capability, too.

Jon
 
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