Bandpass filter coil for Philips D57. Pitch removal.

[Radio Fixer]

Seeking advice from those who have been this way before !

Here is a picture of the coil:

   

Two of the coils top and middle big bulges are open and must be incredibly thin wire to get to 260 and 450 Ohms respectively.

Anyway I am currently soaking in White Spirit for get rid of the pitch.  This normally works but wax was used over the top.  This was to secure the lead out wires and seems to be inhibiting things.

Does anyone know a more effective solvent to use but not one, like cellulose thinners, that would remove varnish from the lead out wires of the good coils>

thanks Gary

[tiv48]

If its wax have you tried heating it wax has quite a low melting point. I have used this method on lopt overwinds that also have very thin wire.
Rob T

[Radio Fixer]

Its a very thin coat of wax so may work ... if no other solvents are recommended I'll give it a try.

"if its made by hand it can be repaired by hand". Going to need a wave wind coil winder, a good one and a lot of operator skill !!

Gary

[Radio Fixer]

Well Tiv using gentle heat did drip off all the wax and a lot of the pitch has come away with soaking in WS. But some remains in softish lumps. It can be eased away with a point but I'm reluctant to do much of this for fear of breaking more connections.

So is there a way of making the dilution more effective? I thought of gently heating the WS or maybe the use of an old ultrasonic cleaner? I'm not too bothered about damaging this and wondered if agitated WS would do the trick. But could it possibly break fine wires at the surface of the coils?

Maybe there is a more effective solvent? Meths or IPA (coming tomorrow) but it mustn't strip enamel.

thanks for thoughts Gary

[Alan Douglas]

What does "white spirit" translate to? Petrol? Should be a good solvent for pitch/tar. Heat almost always increases solvent power, seems like a good idea. Ultrasonic agitation shouldn't break any wires.

On this side of the pond, "tar" was generally what was left after refining oil for gasoline, about worthless but good for filling transformer and capacitor cans (or making "asphalt" roads). It wouldn't be especially soluble in an alcohol.

[Radio Fixer]

White Spirit is Mineral Spirit in the US Alan.

thanks for the ideas.

Gary

[Refugee]

Diesel melts tar too.

[Alan Douglas]

OK, that's a fraction of petroleum too, the heavier part than petrol/gasoline, which grades up through diesel/kerosene, and oils. Should be the ideal solvent for tar (presuming that's what it is).

"Pitch" to me means something that drips from pine trees, but the term gets used for petroleum products here too.

This stuff that Philips used could contain residual acids from the refining process and I suppose could attack copper through any cracks in the wire enamel. You might get lucky and find the breaks are all at the surface.

[Radio Fixer]

I went for the ultrasonic cleaner, filled with WS and after several goes and a little tooth pick work the coils are now clean.

The coils and former are now drying on a soft cloth on top of the boiler. Tomorrow I will see what I have got.

Seemed a lot dangerous than heat !!

Gary