Strange double triode - UK Vintage Radio Repair and Restoration Discussion Forum

vinrads · 29th Oct 2020, 10:30 pm

I have just come across this ,Brimar it is a double triode ct heaters 4/5 and 9 separate cathodes , no markings on the glass ef 80 size , any idea what it is . Mick.

Cobaltblue · 29th Oct 2020, 10:32 pm

12BH7?

Cheers

Mike T

vinrads · 29th Oct 2020, 11:14 pm

That's the one cheers Mike. if only I had two ,Mick.

Diabolical Artificer · 30th Oct 2020, 7:18 am

Those anodes look a bit short for a 12BH7, but can't think what else it would be. The 12BH7 is a very handy valve, great for driving hefty paralleled OP stages. I have some Russian equivalents 6H6N, there's the ECC99 that's close too.

Andy.

G6Tanuki · 30th Oct 2020, 6:53 pm

I'd suggest 12BH7 too; a nice little valve - operated in zero-bias Class-B push-pull it can produce around 5 Watts of audio while making a meagre and satisfyingly-low demand on HT current - great as a modulator-stage in a simple 160-Metre-band AM transmitter!

Cobaltblue · 30th Oct 2020, 7:04 pm

We used 12BH7's in the timing circuits of traffic controllers (type54)

They were operated at just 50V of HT and easily operated post office 2000 series relays.

That's why I instantly recognised it.

If you look at the Brimar example in the Valve Museum I would say the plates are the same length.

http://www.r-type.org/exhib/aaa0177.htm

Late on (Early 80's) when these were coming out of service I did have some example with slightly longer plates but I don't recall the brand.

Cheers

Mike T

boxdoctor · 1st Nov 2020, 3:15 pm

12BH7s were used to drive the reverb spring units in several models of 50s/60s Hammond organs.
A good reliable and fairly rugged (electrically) valve IMHO. Tony.

Restoration73 · 1st Nov 2020, 3:28 pm

Used in my Harmon-Kardon to drive the KT66s. Very good right into the RF spectrum,
used in some RF signal generators.

29th Oct 2020, 10:30 pm	#1
vinrads Dekatron Join Date: Feb 2009 Location: Chesterfield, Derbyshire, UK. Posts: 3,763	Strange double triode I have just come across this ,Brimar it is a double triode ct heaters 4/5 and 9 separate cathodes , no markings on the glass ef 80 size , any idea what it is . Mick. Attached Thumbnails

29th Oct 2020, 10:32 pm	#2
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,875	Re: Strange double triode 12BH7? Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

29th Oct 2020, 11:14 pm	#3
vinrads Dekatron Join Date: Feb 2009 Location: Chesterfield, Derbyshire, UK. Posts: 3,763	Re: Strange double triode That's the one cheers Mike. if only I had two ,Mick.

30th Oct 2020, 7:18 am	#4
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,667	Re: Strange double triode Those anodes look a bit short for a 12BH7, but can't think what else it would be. The 12BH7 is a very handy valve, great for driving hefty paralleled OP stages. I have some Russian equivalents 6H6N, there's the ECC99 that's close too. Andy. __________________ Curiosity hasn't killed this cat...so far.

30th Oct 2020, 6:53 pm	#5
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,005	Re: Strange double triode I'd suggest 12BH7 too; a nice little valve - operated in zero-bias Class-B push-pull it can produce around 5 Watts of audio while making a meagre and satisfyingly-low demand on HT current - great as a modulator-stage in a simple 160-Metre-band AM transmitter!

30th Oct 2020, 7:04 pm	#6
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,875	Re: Strange double triode We used 12BH7's in the timing circuits of traffic controllers (type54) They were operated at just 50V of HT and easily operated post office 2000 series relays. That's why I instantly recognised it. If you look at the Brimar example in the Valve Museum I would say the plates are the same length. http://www.r-type.org/exhib/aaa0177.htm Late on (Early 80's) when these were coming out of service I did have some example with slightly longer plates but I don't recall the brand. Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

1st Nov 2020, 3:15 pm	#7
boxdoctor Rest in Peace Join Date: Sep 2010 Location: Ripley, Derbyshire, UK. Posts: 785	Re: Strange double triode 12BH7s were used to drive the reverb spring units in several models of 50s/60s Hammond organs. A good reliable and fairly rugged (electrically) valve IMHO. Tony.

1st Nov 2020, 3:28 pm	#8
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Strange double triode Used in my Harmon-Kardon to drive the KT66s. Very good right into the RF spectrum, used in some RF signal generators.