Hi Guys,
I've noticed a difference between some 30's and 50's speaker
plugs that plug straight into a chassis.

Of the 50's ones, some can be desoldered at the end of the pins,
so their cords/wires can be replaced.

I've got a 30's plug that looks to be totally moulded around the
pins and wires that were already soldered making it seemingly impossible
to reuse the plug with new wire (at least conventionally).

I've stripped off some pigtails and soldered new wire to them,
but now I don't trust the original wire pigtails won't break off.

I'm wondering if anyone has tried drilling down from the back of the
disassembled plug to reach the pins to solder new wires?

If I lose the plug, the chassis socket also has to be replaced, which I'd rather avoid. Thanks.

Not familiar with that type of plug -- but then I don't work on equipment of that era.

A photo would be good.

Kind of also afraid to unscrew it now, unless I commit to drilling into it.

It's not hard to imagine though. I still think it's bakelite.
Just imagine a flat surface at the back of the plug with wires coming out.

There is a screw on cover for the back,
but it doesn't offer strain relief unless there's a knot inside, but that's difficult if
you've soldered new leads and used heat shrink.
So I just tried to stuff the area as full as I can.

There is a screw on cover for the back

Now I think I know what you mean. Commonly used for speaker connections. Are the wires soldered at the tips of the pins?

Like this:

http://thumbs1.ebaystatic.com/d/l225/m/mqCLOSuxAL2dN5c6N777xbg.jpg.

Yes, both the 30's and 50's examples are soldered at the tips,
but the nasty one I'm talking about doesn't provide access to the backs of the pins
where wire is fed into the hollow part of the pins.

Instead, that part is covered with bakelite,
and only the wires protrude from the physical plug body,
so when you desolder the tips, it might still be impossible
to stick new wire in there without drilling.

the nasty one I'm talking about doesn't provide access to the backs of the pins where wire is fed into the hollow part of the pins.

Can't say I've come across that type. I don't think I'd be wanting to try to re-use it as described, unless desperate -- and in that case I'd be inclined to fill the void with Silastic or similar.

If you post a photo of the plug in question we may be able to suggest a replacement.

Can't remember seeing a totally sealed bakelite plug of that era.

We do need photo's. May just have a screw cap lots did.

Un-soldering wires in hollow pins is not difficult,

Marc

Do you know what radio and/or speaker the plug originally belonged to? Might then be able to track down one of these plugs. Were the original wires and/or cord cotton covered?

Bakelite mouldings are made at about 140C and 4000psi. If the insulation can stand those conditions shouldn't be a problem to mould the wire in. Bakelite might squeeze between the wire and the hole in the mould it comes through at 4000psi though.

I haven't been able to find anyone with an Airzone chassis for parts, but that's what it's from.
Two pins are bigger because it's a field coil speaker.

Like I said, afraid to pull it apart again for no reason, but:
Image Link

Don't mistake this for the type that has exposed pins at the back.
I dealt with this.. piece of cake.
Image Link

It's a bit hard to see in the photo and I imagine you've already checked, but does the back section unscrew? It looks like a join near the flange.

Yes, the back section of both plugs can unscrew,
but only one reveals the backs of the pins,
the other reveals a flat surface of bakelite with what is
now four stripped wires coming out of them.
Those pigtails are now soldered to new wire, and individually covered in heat shrink.

I think silicone is my best bet.. just filling in all area that is not used.

Faced with that, I'd try to fill the pigtails with solder right down to the surface and hopefully some distance into the bakelite, using plenty of flux, to form a solid and stable solder pad. Then any wires soldered to those pads can be stabilised with silicone or similar, as you are planning. My concern would be that any pigtails that could flex at all would eventually break off at the bakelite.

Maven