[morzh]

Just ordered the acrylic CC.

[Eliot Ness]

I would use Q-Dope, mainly because I already have some on hand:

Q-Dope is a solution of pure polystyrene in solvents. Dries fast and leaves a clear, protective coating on coils and transformers, with no or minimal effect on inductive values. May also be used as a cement for molded or fabricated items made of polystyrene. 2 oz. bottle.

Ron, that is interesting info on the silicone.  

[morzh]

Q-dope, is it the Corona Dope by the same company? Used it before. Not sure whether it is benign on wire lacquer, I remember strong acetone smell.
Might be a different one though.

The silicone Ron was referring to was likely a potting silicone rubber or sealant, not likely a conformal coating. I do not think a conformal coating specifically recommended for PCBs would be popular if it were copper-corrosive. Then a product that is different, and is silicone-based, might be.

[Eliot Ness]

Yeah, I doubt that a conformal coating made for PCB work would be corrosive to cooper.  I think what Ron was referring to was something like a silicone caulk, which I would not have thought it to be corrosive to cooper either, so that's good to know.  Otherwise I might have used some to re-pot with sometime.

Since Q-Dope is safe for coils I don't think it would harm the coating on the wire, but it sure wouldn't be a bad idea to test it first!

[morzh]

Actually all coils in Atwater Kent are potted with something really black and shiny, looks like Q-dope. Made it impossible to re-wire. Had to solder to existing rubber-coated wire and heat shrink.

[Ron Ramirez]

Yeah, I doubt that a conformal coating made for PCB work would be corrosive to cooper.

Agreed.

Silicone caulk, however, is a definite no-no and will corrode copper.

[Arran]

 What makes the silicone corrosive is not the silicone so much as the acetic acid often used as a curing agent, it has an vinegar smell to it. There are types of silicone that are safe around copper though, any automotive sealant marked as "Sensor Safe" would be all right to use, I suspect that Permatex windshield and glass adhesive may be safe as well since it does not have that vinegar smell. Varnish and wax are safe though, but some melt at too low of a temperature.
Regards
Arran

[morzh]

Well, just to remind, we are talking of conformal coating.


It is not a caulk, it is not a bulk gooey stuff, it is not a sealant in a tube that one applies as a bead, it is a sprayed or brushed fairly quick drying substance to form a film. And it is intended to be used on electronics, namely on PCBs with copper conductors. So, silicone or not, it is inherently safe for most everything that is on the board or board itself, and all that contains copper.

There are always some components that require special treatment, like say Vicor power supplies explicitly warn against aqueous wash etc etc, so if there is a component is sensitive to conformal coating, or to a particular kind of it, it will be listed in its datasheet explicitly and conspicuously. What's more, the coating itself then would likely state "do not apply to copper parts" on the packaging label.

The key to safe and effective usage is using products according to their intended usage and observing labels/datasheets.

Granted we all sometimes have to use things off-label, then it is warranted that one does some research prior to doing this.

[palegreenthumb]

Was just reading this thread, then happened across a similar radio on RadioAttic only minutes later for a completely unrelated reason.

Don't know if it's relevant to the thread, but thought I'd throw it in here:
http://www.radioattic.com/item.htm?radio=1000242

[morzh]

Yes model 43 is close, so is model 41, but the 41 is the only sch that has been found so far.
There are differences though.

[OldRestorer]

weird because I have this radio but the escutcheon is a tiny bit different and the chassis is completely different it is a silvertone 1954.

Hmmm

Kirk

[morzh]

They obviosly used chassis from different mfrs.

[morzh]

OK, got to the other coil.
Good news: the largest coil is open, was able to count turns.
The other two are good. I am inclined to reuse the bobbin and the two existing coils if it proves sturdy enough, as one of them is some thick litz wire, and I don't have any.

Will see....

[morzh]

This is the second coil.

Before

   
   

After

   
   
   

[morzh]

...and installed.


The wires coming from inside the chassis plus the ground wire attached to the bracket give it enough rigidity.....well, as it was before anyway. Otherwise I'd have to make a new bobbin, and then the whole coil would have to be re-wound.

   


Once the conformal compound comes, I will install the first coil, fix the wire on the IF coil underneath and ..... fire it up!