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 Can't remove solder from chassis

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herromc



Join date : 2017-08-26

PostSubject: Can't remove solder from chassis   2017-08-27, 12:24 pm

I have an extra chassis for my Grunow 1191 radio that I want to restore.  At present, it is totally empty, just the chassis.  First of all, I'm new at all this restoration stuff.  Anyway inside the chassis there are three tabs sticking up, which had, what looks like, braided copper grounding straps soldered to them.  I tried to desolder the tabs, but with no luck.  I have a soldering station, and had the temp up as far as it goes (896 degrees), but it did little to nothing on the old solder.  I melted new solder onto it, hoping that would help, but no.  Does anyone have suggestions on how to remove the old solder? 

Thanking you in advance,

Mike (herromc)

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Dan Walker



Join date : 2016-12-02

PostSubject: Re: Can't remove solder from chassis   2017-08-28, 7:21 am

You not going to remove the solder with  the soldering unit you have .  There is just not enough
heat .. What you need is one of those large old soldering irons; the ones with the triangular ends.
 they are used for soldering chassis .
 other than that you might try a Weller soldering gun as it has a bit more area of heat.
  Dan in Calgary
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chas

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Join date : 2017-04-09

PostSubject: Re: Can't remove solder from chassis   2017-08-28, 7:27 am

The joint has too much thermal mass and acts like a heat sink...

It is the ability or not of the soldering tool to store/hold/deliver calories to the joint.

A soldering iron with a large copper mass from 125 watts and up will do the job. Since the chassis is clear of other components a 250 watt American-Beauty (still in business) or a Vulcan (orphan) with a large copper bolt will work to. These irons, when new, are expensive, don't pass them by at yard sales as long as the power cord is still serviceable.

You can also use a torch but excess heat on a plated chassis can liberate poisonous (long term exposure) fumes from zinc or cadmium. So does grinding and sanding from solder/cadmium dust.

A vintage soldering bolt (iron) that is heated on the gas stove will work too. You will need one about an inch in diameter and three inches long at the business end.

Certain (vintage) Weller 250 or so watt soldering guns may work. Proof that the soldering tool is adequate is touching the work and removing the wires in 5-10 seconds time means there is enough stored calories to do the job.

One other trick that works in many instances is the application of fresh solder or reduced melting point solder to the joint.

The act of soldering amalgamates the surfaces of the base metals to the solder raising the melting point. For some joints 50/50 solder was used. By adding fresh solder, the melting point is reduced and often stubborn joints will flow with a smaller capacity iron...

GL

Chas
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herromc



Join date : 2017-08-26

PostSubject: Re: Can't remove solder from chassis   2017-08-28, 8:05 am

Vulcan Electric "Mercury" #6 Soldering Iron 150 Watt

Chas, do you think this one would work, "Vulcan "Mercury" #6 Soldering Iron 150 watt"?  See photo.


Thanks,

Mike


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Cliff Jones
Site Administrator
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Join date : 2010-11-22

PostSubject: Re: Can't remove solder from chassis   2017-08-28, 8:07 pm

Using that monster should work and use it with your other desolderer if necessary.
clean it up first, (Both the soldering irons and that wire tab connection), apply liberal amounts of flux and fresh solder Eutectic works best (63/47) as it has a lower melting point.

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herromc



Join date : 2017-08-26

PostSubject: Re: Can't remove solder from chassis   2017-08-28, 8:26 pm

Thanks for the info.

Mike
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19&41

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Join date : 2014-08-19

PostSubject: Re: Can't remove solder from chassis   2017-08-29, 11:30 am

I have a Weller D550 that does very nicely on chassis soldering and doesn't take up space during heating and cooling as much as an iron.  They can be found on Ebay at less than retail.

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"Any sufficiently advanced technology is indistinguishable from magic."
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chas

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Join date : 2017-04-09

PostSubject: Re: Can't remove solder from chassis   2017-08-29, 5:34 pm

Mike,

That old Vulcan iron looks ideal!

Clean it up as advised. Most of the irons were built for 110-115 so at todays 125-130 the iron will get quite hot and rapidly oxidize the tin out of the solder.

You can control the excess heat with a variable transformer.

I do this even with my small pencil 40 watt Ungar, usually running 100 volts or so...

Turning down the voltage is not a thermostat. Sitting idle even at 100 volts an iron will gradually rise in temperature.

The Vulcan has a large body that is hot, it can give severe burns, set up the iron with some kind of non-combustible supporter like a heavy wire cradle to set it in. A large iron can easily set paper alight.

Chas

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herromc



Join date : 2017-08-26

PostSubject: Re: Can't remove solder from chassis   2017-08-29, 5:50 pm

Thanks for all the help.

Mike
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Cliff Jones
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Join date : 2010-11-22

PostSubject: Re: Can't remove solder from chassis   2017-08-30, 1:13 pm

also, you could make an ordinary light bulb such as a 75watt to work in series with the soldering Iron to limit the wattage. and the second benefit is that as long as the bulb is lit you know the iron is still on and HOT

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