does anyone know the trick to pre tin the leads on mtx-90 tubes

[Jasper nagle]

tubes im having no luck putting tin to them i even managed to tin the painted surface i was working on in the process 

[Batareyka]

H3PO4
or
H3PO4 + HCl (10:1)

пятница, 24 марта 2023 г. в 12:33:31 UTC+2, Jasper nagle:

[Jasper nagle]

thanks for that

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[Paul Andrews]

I had read that the little balls on the ends of the leads are solder. Is that not true?

[Jasper nagle]

Yes that is true but I’m working with some used ones that have been cut 

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[Yohan Park]

No that's not true. It's not solder but a different metal (can't recall what it is) to make it easy to solder. You won't be able to melt the blobs with your soldering iron though.

[Jasper nagle]

I was able to melt the blobs on the mtx-90 with a soldering iron so it must be something like tin or lead 

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[Yohan Park]

Just tried with my iron set to the highest temperature (480C/896F), added lead based solder to try to make it going but nothing happened.
So either you're soldering at insanely high temperatures or they've used different materials over the years... :)

[Jasper nagle]

 Maybe I have another go at the blobs tomorrow on a few different tubes I’ll see if age makes a difference 

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[Batareyka]

mth-90 used solder with a high lead content. Therefore, for a long time of non-use, the balls on the legs of the solder oxidize and form a rather large film of oxide that prevents the metal itself from melting.
To do this, you need to remove the plaque to a shiny with anything, a file or a knife.
And after that, everything is soldered quite easily.

суббота, 29 апреля 2023 г. в 19:31:58 UTC+3, Jasper nagle:

[Paul Andrews]

Interesting. Maybe time to break the flux out? Works for me on old radios.

On Apr 29, 2023, at 12:37 PM, Batareyka <batar...@gmail.com> wrote:



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[gregebert]

Usually when I cant solder something it's because there is too much surface oxidation. Some of it gets so bad that rosin-based flux wont dissolve it, so the next step is to scrape it off with sandpaper, or a dremel tool.

So far, the worst I've encountered are

• Oxidized copper leads on bulk neon bulbs from China
• Lugs on very old switches, pots, and lamp sockets that were not previously soldered
• Really old resistors that were never used.....from the 1950s and 1960s
• Stranded copper wire that mysteriously corroded *beneath* the insulation. I suspect there was a slow chemical reaction between the copper and something that outgassed from the plastic insulation.

[padler...@gmail.com]

Ditto on the stranded copper wire. One of the most frustrating things and almost impossible to clean the strands well enough for the solder to wet and make a reliable connection. 

Randy 

On May 1, 2023, at 4:58 PM, gregebert <greg...@hotmail.com> wrote:

Usually when I cant solder something it's because there is too much surface oxidation. Some of it gets so bad that rosin-based flux wont dissolve it, so the next step is to scrape it off with sandpaper, or a dremel tool.

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[Benoit Tourret]

you should try phosphoric acid ( H3PO4 ) , it works great for rust and oxyded copper.

if some black foam appears, that is the zinc (Zn) witch is dissolved.

it also stains stainless steel sinks.

[gregebert]

Next time I find a hopelessly stubborn item to solder, I'm going to get my version of "The Holy Hand Grenade of Antioch"   -- acid-core solder.

I've always wanted to know if the corrosive flux can be safely and adequately removed, and possibly over-coated with rosin-based solder.

I rarely use this stuff; in the past it's always been for steel parts but that ended when I got an oxyacetylene torch and now I just braze those items.

[Jasper nagle]

Ok thanks 

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[Nicholas Stock]

+1 for the Monty Python reference.... thanks Greg!

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