Unknown valve - UK Vintage Radio Repair and Restoration Discussion Forum

retailer · 5th Jul 2020, 12:54 pm

These came in a box of valves I bought some years back - I can't find any any references with google, bing etc. The top dome has the Cossor logo with "made in England" a "1" above the word Cossor and V9 underneath, on the side is TMC 18, pentode with B7 base. Many of the other valves in the box have been identified as GPO or post office valves. Any assistance in identifying is appreciated.

turretslug · 5th Jul 2020, 2:35 pm

It looks quite like the Cossor-branded MKT4 in the Marconi 559 here- in an age of bulbous valves, Cossor seemed to make them more bulbous than most. Note that there were both early 5-pin and later 7-pin versions when searching,

Colin

Heatercathodeshort · 5th Jul 2020, 3:26 pm

It's my guess that they are telephone line amplifiers. TMC18 sounds like Telephone Manufacturing Company that used to be behind the museum at Dulwich. John.

AC/HL · 5th Jul 2020, 4:18 pm

Quote:

Originally Posted by turretslug

in an age of bulbous valves, Cossor seemed to make them more bulbous than most.

To get more vacuum in!

retailer · 8th Jul 2020, 3:16 am

Thanks for the id of the valve - certainly looks like a MKT4 or possibly a MPT4 as it looks like a straight pentode, other valves in amongst them were AC/Pen and Pen36A - with the exception of filament voltage these all seem to have similar specs.

turretslug · 8th Jul 2020, 10:24 am

It seems that there was a good deal of equivocation/obfuscation in the kinkless tetrode/pentode marketing stakes at the time, this entry from The Valve Museum is a good case in point,

http://www.r-type.org/exhib/aad0084.htm

The specimen illustrated looks to have a box radiator at the top of the control grid rods, but is otherwise fairly similar-looking.

5th Jul 2020, 12:54 pm	#1
retailer Heptode Join Date: May 2005 Location: Adelaide, South Australia Posts: 541	Unknown valve These came in a box of valves I bought some years back - I can't find any any references with google, bing etc. The top dome has the Cossor logo with "made in England" a "1" above the word Cossor and V9 underneath, on the side is TMC 18, pentode with B7 base. Many of the other valves in the box have been identified as GPO or post office valves. Any assistance in identifying is appreciated. Attached Thumbnails

5th Jul 2020, 2:35 pm	#2
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,394	Re: Unknown valve It looks quite like the Cossor-branded MKT4 in the Marconi 559 here- in an age of bulbous valves, Cossor seemed to make them more bulbous than most. Note that there were both early 5-pin and later 7-pin versions when searching, Colin

5th Jul 2020, 3:26 pm	#3
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Unknown valve It's my guess that they are telephone line amplifiers. TMC18 sounds like Telephone Manufacturing Company that used to be behind the museum at Dulwich. John.

8th Jul 2020, 3:16 am	#5
retailer Heptode Join Date: May 2005 Location: Adelaide, South Australia Posts: 541	Re: Unknown valve Thanks for the id of the valve - certainly looks like a MKT4 or possibly a MPT4 as it looks like a straight pentode, other valves in amongst them were AC/Pen and Pen36A - with the exception of filament voltage these all seem to have similar specs.

8th Jul 2020, 10:24 am	#6
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,394	Re: Unknown valve It seems that there was a good deal of equivocation/obfuscation in the kinkless tetrode/pentode marketing stakes at the time, this entry from The Valve Museum is a good case in point, http://www.r-type.org/exhib/aad0084.htm The specimen illustrated looks to have a box radiator at the top of the control grid rods, but is otherwise fairly similar-looking.