WWII Telephone Set D. MK V - Handset No.2 - Receiver Problem

[hatrick]

I recently picked up a WWII Telephone Set D. MK V but unfortunately there is no sound coming from the handset. I did some testing and checking with my other field phones and it looks like the wiring in the transistors in the handset receiver is damaged. I need to find either another WWII dated Handset No.2 or the transistor piece that goes into the headset (see picture below).


[IMG]http://farm4.static.***********/3013/3051800731_952d86965b_z.jpg?zz=1[/IMG]

I could also use a No. 3 handset from the Telephone Type F Mk I if someone has an extra one of those lying around.

Any help would be greatly appreciated.

Thanks,
Eric

[russell_w_b]

Transistors, eh? It'll be tubes in them old telephones!

Have you a multimeter with an 'Ohms' range on it? You might have an open-circuit bobbin. How did you test? If no multimeter to hand, remove the receiver by extracting the two large cheese-headed screws and lifting the receiver from the handset.

Mount the receiver in the handset of a known 'worker' and see what happens. Conversely, you could mount the receiver of a known 'worker' into your suspect handset and see if it works.

[hatrick]

Russell,

I probably blew it saying transistors. the piece that seems to be faulty is the two wire wrapped pieces in the center of the earpiece as shown in the picture above. The wires are corroded and broken although I do feel power coming to the two posts that connect to them. The entire assemble comes out as a single unit and I'm hoping to find a replacement assembly or even a complete No.3 or No.2 handset.

Thanks,
Eric

[Station X]

The two "wire wrapped" pieces are electromagnetic coils. A varying current flowing through them attracts the diaphram generating sound waves.

The two coils should be wired in series and connected across the handset cord. Even though the wires are corroded and broken it should be possible to solder them together again. I would check the coils for continuity using a meter on ohms range first though.

[russell_w_b]

Originally Posted by hatrick

I'm hoping to find a replacement assembly or even a complete No.3 or No.2 handset.

Eric,

You should be able to pick up a spare receiver insert, as they were a standard fitting on UK and Commonwealth telephones from the 1930s - 1940s, with a more modern insert available on models produced from the 1940s - 1960s.

They were produced by various manufacturers (the GPO used the type 1L and 2P) like GEC, Ericsson, Siemens, TMC, etc...

Althouth the later model will fit (see here to spot the difference), in the interests of authenticity, you might like to use the older 1L type, as the 2P variant is designed for a different threaded earpiece and will protrude slightly more if the original 'pepper-pot' earpiece is used.

If you wish to convert your telephone to practical use and damn the authenticity, you could try to get hold of a rocking armature receiver and an adaptor collar, as were fitted to some UK military telephones.

Maybe Canada is the place to look? UK-manufactured telephones were made, and used, there.

[hatrick]

Thanks for all the great info!! The wire that connected the two electromagnetic coils was corroded and broken and I tried unwrapping a bit from each coil and then twisting them together and then wrapping the coils again with electrical tape as I had to remove the original coating on the coils. I then re-soldered each coil to its post but still nothing. There is current coming to the posts as I can feel it if I touch both posts at the same time. I'm not sure what is going on with the coils but I suspect they are shot.

Does anyone have or know where I can find a replacement receiver insert??

Russell's info is very through and either model replacement would work for me although an original, Receiver, Inset No.1L style would be preferred. Out of curiosity, what does GPO stand for


Thanks,
Eric

[Station X]

GPO = General Post Office. They used to run the UK Telephone Service.

Did you strip the insulation from the coil wires before taping them together?

Have you checked the DC resistance of the coils with a meter?

[hatrick]

The coil wires didn't seem to have any insulation on them. I had to remove the casing that each coil was wrapped in so I could un-wind a bit of wire to twist together to connect the two coils again but the individual wires don't have any casing.

How would I check the DC resistance??

Thanks,
Eric

[julie_m]

The wires will be coated with a thin layer of enamel varnish. You can remove it and so expose the copper underneath by scraping with a sharp blade, burning it off with a cigarette lighter or dipping in acetone. All these courses of action are potentially dangerous, so be careful .....

[russell_w_b]

Originally Posted by hatrick

How would I check the DC resistance??

With a multimeter is easiest. A general-purpose one is not expensive, and will open up your opportunities for repair, curiosity, etc... Or you could borrow one from someone.

The DC resistance of a complete receiver like yours is typically 80 - 88 Ohms. Both electomagnets (or 'bobbins') should be about equal: 40 - 44 Ohms.

[hatrick]

AJS,

That did the trick!! Burning off the varnish on the wires where I spliced them together seemed to do it. Thanks for the tip!!

Eric

[Darren-UK]

A completely unrelated post regarding a GEC Set F has been moved to here.