Desoldering question (Miller XMT welder repair)

"Ignoramus1782" wrote

Two words.

Solder wick.

Obviously it should provide enough to remove molten solder from the joint.

Most desolder tools can get blocked. So check the pump with the tool disconnected you should feel the vacuum with your finger. Also check the output air stream from the pump. Many have an adjustable restrictor valve to set the vacuum level. If it's been used without the proper filters it's possible the pump is dirty, blocked or damaged. They usually strip down easily. The one Pace I've had apart had sort of carbon vanes which move in slots to make contact with the body by centrifugal force. If those were stuck it wouldn't work properly.

Ignoramus1782 fired this volley in news:EqOdnRGHEfpSgz3anZ2dnUVZ snipped-for-privacy@giganews.com:

Iggy, there are four things that go wrong with the Pace stations, and at least two of them are "intentional".

In the solder collection tube is a serpentine piece of aluminum strapping used to trap and cool the solder. That can collect so much flux and metal that nothing can get past it in the collector.

Upwind (vacuum side) of the strap is a cotton felt plug used to prevent droplets from passing into the vacuum line. It gets solid-filled with flux vapor, and will fail to pass air. Just massage it in a beaker of denatured alcohol to clean it, then thoroughly dry it before re-use. Replace if it's too gunked up with solder chips.

Further upwind, inside the base is a pancake filter. It, too will get rosin vapor deposited on the fabric. Once plugged, you must replace it.

Those are the three Intentional blockages -- all protection features of the system.

The fourth area of failure is the vane pump. It has graphite vanes and end-plates. They wear. They can be replaced easily, if you access to the parts.

LLoyd

You don't have a proper desolder tool, then? ;-)

I often use solder wick as mentioned, an air nozzle using compressed air often works (blows solder out, cools board, trace, component), my desoldering gun with the rubber bulb works too. One of these days I need to try hooking up a shop vac to my dead solder sucker and see how that works also.

Wes

I cleaned the tube, but there was not that much to begin with, a few globs.

A great idea, I will check it.

Will check out, thanks.

Great, last time I checked, Pace was still around. Thanks Lloyd. I will try to approach it systematically, trying to isolate the problem. I believe that it is something inside the unit.

You know, Wes, somehow I am a little terrified of blowing hot solder with compressed air. :)

I am also doubtful that shopvac would provide enough suction.

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.

Exactly.

I think that I would like to find Cirk-Grind device and also should buy more tips. This is actually a very nice station if I get it to its potential. I do have a manual for it also.

Ignoramus19508 fired this volley in news:NdOdnTFNr5aYPz3anZ2dnUVZ snipped-for-privacy@giganews.com:

Iggy, it's been a while since I had my Pace, but IIRC, those tips are plated with Indium/Nickle alloy to prevent them from being wetted by or amalgamated with the solder -- even in the bore. Thus, don't use a hard tool to clean the bore; use a plated copper lead from a resistor, etc. If you scratch the bore, it quickly begins to corrode and amalgamate with solder.

I think I still have some 0.025 tips for that. If I can find them, I'll drop 'em in an envelope.

LLoyd

Lloyd, this is awesome, thanks.

Another question. These circuit boards were originally sprayed with some coating. I surmise that the purpose of it is to prevent accidental shorts due to dust contamination or other debris being drawn into the unit.

This was, in fact, a great thing, as this particular welder had so much dust inside, that I was shocked. The amount of dust was nothing short of incredible, maybe 5 lbs of dust settled on absolutely 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.

Thanks to the Miller company.

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

Ignoramus19508 wrote in news:TpSdnYx38KcYWj3anZ2dnUVZ snipped-for-privacy@giganews.com:

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

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.

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.

There are several kinds of varnish and conformal coating that will work; for small jobs, I usually use clear nail polish. Q-dope and some mil-spec moisture/fungus resistant coatings are the usual things elecronic suppliers will have for this purpose.

Don, which one would you recommend, I will buy whatever you think is the right one.

To use them, you need to have a soldering gun in one hand and pump in the other hand, right?

Yes, I obviously have no knowledge or skill to work with modern, miniature circuit boards. But the stuff like that Miller display, I could fix.

Miller, also, has done a great job at making repairable circuit boards.

The one I have is the DS017, their original model. If you work much with very static-sensitive circuitry than the DS017LS might be a good choice.

Yes. Get the joint thoroughly molten, adding solder if necessary, then apply tip of soldersucker and push the button. Thuup! If it's a part on a printed wiring board, it often works best to suck out the holes from the non-component side because the sucker tip has a clear shot at the hole.

It doesn't always suck the joint clear dry, but usually dry enough that wires and leads can then be jiggled or popped loose. Sometimes parts just fall out, but not always.

I have developed the habit of flipping my wrist and whacking the plunger on the bench to recock after each use. Then it's ready to go when the next joint is melted.