RS1b EMIM repair. Need Help

[wsill]

Hello everyone,
Yesterday one of my EMIM's just stopped working #6 in the series connection 5,6,7.
I took it apart I don't see any burning or cracks in the leads. I put a 3 ohm resistor in its place to check out # 5 and 7 EMIM they are working now.
So with the failed #5 ; When I test between continuity between + and - terminals just get open circuit. When I test between + input and the traces seems like I have continuity all the way around.
But when I go to the negative terminal I have no continuity anywhere. I tried to reflow the solder on the negative terminal but the solder just bunched up on the input terminal just flow onto the foil.
Is there a special solder I need ?
What else should I check or try?
Any thoughts here ?

I attached two pictures of my failed EMIM.

Thanks all,
Bill

Before solder reflow After I tried to reflow

 

[jazzmans]

It's aluminum solder you need, but now you're better off looking at Graz's emim replacement, if bobbyd doesn't yet have his emim's for sale.

 

[pauljh]

It's aluminum solder you need.

THAT is useful information. Thanks jazzmans.

 

[wsill]

I agree about the aluminum solder but I don't know how to use it.
The aluminum solder I have seen doesn't melt until 1050 degrees, needing a torch to melt.
Normal solder melting is around 400 degrees using a soldering iron.
If you take a torch to the EMIM panel you'll melt it instantly. Unless someone knows of a way to drip the aluminum solder unto the panel.

Anyone have any ideas?

I did check with bobbyd on the EMIM's, he's not ready yet.

Thanks all,
Bill

 

[seifreit]

Maybe this will help,

https://superiorflux.com/papers/TWJ.May.2018.Tech.Solder.Al.pdf

 

[okeeteekid]

Why not try this https://www.amazon.com/MG-Chemicals...older+epoxy&qid=1609908406&sr=8-2&tag=mh0b-20

 

[ericw]

You could also try a rear window defogger repair kit, since the connection point isn't on the moving part of the diaphragm.

 

[okeeteekid]

I used the epoxy on one once, worked great, I couldn't hear a difference between the one I repaired and a stock one, also as time went by the epoxy made better contact, I think when the epoxy dries out the silver in it contacts even more

 

[wsill]

Thank You to seifreit, okeeteekid, ericw for the suggestions - I like the window defogger and epoxy solutions.
I will let you know the option I try and the results.
In the meantime I ordered an EMIM from Dr. Marks. Its planned for delivery tomorrow.
Bill

 

[elnaldo]

AFAIK, to solder this kind of aluminum surfaces, you need a special flux to prepare the surface, and then solder with regular solder. The aluminum solder you have seen is to solder solid aluminum pipes and those applications. Anyway I'd ask an expert before trying in a good EMIM.