Mystery Cossor valve

[petervk2mlg]

Does anyone have any data on this Cossor indirectly heated triode type TMC15B. B5 base.
I have a few of them. Some have the Cossor brand on top, others don't.

I've found that it's equivalent to a CV3730 but don't have any data on that either. Cold DC resistance of the heater is 17 Ohms.

[high_vacuum_house]

I wonder if TMC is for Telephone Manufacturing Company and is part of an amplifier for a telephone repeater. It does look like a sturdy valve.
TMC15B being an internal part number.
Christopher Capener

[Catkins]

History of TMC https://www.britishtelephones.com/histtr.htm

According to this page (http://www.pyemuseum.org/divisions/c...ucts/radar.php) TMC was involved in the production of radar equipment in the war.

Later, EKCO, Cossor, TMC, TGC and Dynatron took over the volume production of the radar equipment and Pye concentrated on the land warfare sets for the Army

This would explain why the valve has a military CV number, and the fact it is made by Cossor.

[TonyDuell]

My experience is that the transistors (at least) used in P.O. telephone equipment had CV numbers too.

[retailer]

I have some similar valves that came in a large box of valves I aquired some years back, one lot are pentodes, 4V filament B7 base, a few are marked Cossor on the top the TMC code is TCM18,
The other lot are triodes 12.5V filament B7 base grid to the top cap and mesh anode, I think they are close equivalent to the HL13C

[petervk2mlg]

Many thanks for all the answers gentlemen. I took a punt and tried one of the valves in a home brew amplifier with 4 volts on the filament. No response. I gambled and tried upping the filament voltage to 15 volts. The heater glowed nicely and the valve worked.

[barrymagrec]

Originally Posted by TonyDuell

My experience is that the transistors (at least) used in P.O. telephone equipment had CV numbers too.

Yes, I have some CV358s (EF37A) that originated from the GPO.

[Mr Moose]

Hello.

The electrode structure of the TMC15B is very similar to the Cossor 41-MTA triode ( http://www.r-type.org/exhib/abd0013.htm ) but with a higher voltage heater.

As to retailers valves, the one with a top cap appears to be a GPO (General Post Office) VT100B valve ( https://www.radiomuseum.org/tubes/tube_vt100b.html ) which does appear to be equivalent to a HL13C.

Yours, Richard

[petervk2mlg]

There seem to be 4 heater wires in the TMC15B or have I got that wrong?

[Richard]

Originally Posted by petervk2mlg

There seem to be 4 heater wires in the TMC15B or have I got that wrong?

Built in redundancy maybe?

If one fails the other one switches in so it keeps working?

Richard