"Ignoramus1782" wrote in message
...
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.

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?

Any experience here?


My Weller 900 desoldering station, is of exactly the same construction, and
probably similar vintage. It has a vacuum gauge on the front, that reaches a
reading of "-0.6" - so I guess that's 0.4 atmospheres - when it is working
normally. But that's the trick to it. It works extremely well when it *is*
working well. It develops enough suck to be able to hear it 'slurp' up the
solder from a joint, and will readily remove solder from around IC pins in a
thru' plated hole board - an action that's notoriously difficult to achieve.

But when it's not working well, then man, it's a dog. It requires regular
maintenance of making sure that the hole in the nozzle is clear, using the
proper ream-out tool, every few sucked joints. About once a week, I clear
out the passage between the tip, and the solder collection chamber, again
using the proper reamer. Once a month, it will need the chamber cleaning
out, and the felt filter at the rear, just before the vacuum connection
point, replacing or cleaning. Once every couple of months, it will need the
front collection chamber gasket replacing, as the silicon rubber goes hard.
Occasionally, a blob of solder will get past the filter, and lodge in the
vacuum tube. It can get sucked quite a way in, so it's worth feeling all the
way back to the vacuum pump unit, to make sure that there is nothing in
there.

About once every 6 months, I clean out the main vacuum passageways. That's
all of the solid pipe stubs that the various flexible pipes plug onto. It
includes the ones at either end of the main flexi to the iron, and also the
ones to the 'flywheel' chamber inside the base station. This also serves as
the holder for the station's own protection filter - which should be
replaced at this time, along with the exhaust filter - and the connection
point for the vacuum gauge. The final one is on the vacuum pump itself.
Despite all of the filters that are in line, all of these vacuum passageways
get clogged with solidified flux residue, which is very sticky like tar, and
needs poking out with a fine screwdriver blade, before finishing off with a
flux solvent. This clogging up of these tubes has a *very* significant
impact on the performance of the unit, and is the difference between the
thing being a pleasure to use, and a royal pain in the arse.

About once a year, I strip out the vacuum pump itself, and clean all of the
passageways, and the little rubber flap valves, which also get coated in
flux residue. Hope this helps you get a handle on how well your Pace
*should* work, as I should think that it is pretty similar to my Weller.

Arfa