B8B / B8G bases - difference? - UK Vintage Radio Repair and Restoration Discussion Forum

Jeremy M0RVB · 22nd Feb 2016, 2:20 pm

Hi

Does anyone know the difference between a B8B and a B8G valve base?

I've seen many 8-pin lock-in types listed as B8B, and I've seen both types described as loctal, but the CV datasheets for them show the base as B8G - e.g. EL22 / CV304, 3A/167M / CV5221

Is it that the B8B does not have the spigot lock? I have some developmental valves which do not, e.g. this 'prototype' KT101: http://www.tubecollector.org/e1796.htm

Jeremy

FERNSEH · 23rd Feb 2016, 2:38 am

Hi Jeremy, I've always been aware of the B8G and B8B valve bases and like you have wondered what is the difference between the two.
The B8G base was developed by Sylvania and is also to be found on valve types made by various manufactures. Valves developed by Sylvania with the B8G base are the 7S7, 7C5, 14S7 etc. The Philips valves with the B8G are the ECH21, EBL21, UCH21 etc. The Brimar 5B254M series also has the B8G base.

From the Radiomuseum: Description The Philips 21- "Key Base" tubes were initially designed in 1940 with the 9-pin base B9G like the EF50. The later series production from 1942 on however was changed to the 8-pin Locktal-base B8G designed by Sylvania.

So perhaps the only difference is the style of centre spigot?

DFWB.

Jeremy M0RVB · 23rd Feb 2016, 12:54 pm

Hi

Quote:

Originally Posted by FERNSEH

From the Radiomuseum: [I]Description The Philips 21- "Key Base" tubes were initially designed in 1940 with the 9-pin base B9G like the EF50. The later series production from 1942 on however was changed to the 8-pin Locktal-base B8G designed by Sylvania.

That sounds hopeful, thanks.

Rather annoyingly my copy of BS448 - the valve base 'bible' is 1953 and only lists the B8G. There are 3 or 4 earlier editions but our academic access only gives access to the latest (1981) edition. I bet the B8B spec is in one of those earlier ones. Mind you that's only if it became a British Standard of course.

I've also posed the question on the Tube Collectors Association list and i'll feed back either way.

turretslug · 23rd Feb 2016, 2:34 pm

Something rings a bell that there were even early 9-pin and later 8-pin versions of the ECH21, the later version having cathode connected to the spigot.... Calling the B9G variant "locktal-9" seems contradictory in itself. Could it be that B8B was the officially chosen designation but B8G became used colloqially because of the B9G association?

I have versions of the same valve, eg KT81, W81 and so on that have both thermoset and diecast alloy bottomed incarnations- both strike me as additional manufacturing expense as the era of glass button base valves commenced. Seemingly a bit like the B8a/lockfit series in being a relatively short-lived diversion.

FERNSEH · 23rd Feb 2016, 6:25 pm

From one of the Babani books. A list of 8 and 9 pin tube bases. The B8G is shown with the centre spigot as a 9th pin. Used as the cathode connection on the E(U)CH21 triode-heptode.
The base "L" is the one fitted on the Sylvania all glass 7B7, 7S7 and 7C5 tubes. We know this base also as B8G.
No reference to a B8B base in the book.

DFWB.

FERNSEH · 23rd Feb 2016, 7:39 pm

The Quarrington book "Radio circuits and Data" refers to the loctal base as B8B and this is the base employed on the Philips/Mullard ECH21 and EF22 as well as the Sylvania developed 7S7, 7C5 etc. Also the battery output pentode, the 3D6. From the Valve Museum: http://www.r-type.org/exhib/aad0188.htm
The loctal base is described as "B8B".
So at least we now know there was a valve base designated as "B8B".

DFWB.

turretslug · 24th Feb 2016, 10:27 am

The BRT400's manual also refers to "B8B" types, so the designation appears to have been around at least to start with. Perhaps they were designations from opposite sides of the Atlantic for bases that were marginally different in some detail but which were interchangeable for practical purposes. I sometimes wonder if this sort of differentiation comes about for commercial/legal loophole purposes as opposed to purely technical reasons.

Tsk!- I should have said "B8a/rimlock", not "B8a/lockfit" above

Jeremy M0RVB · 25th Feb 2016, 4:14 pm

Well I found a little more, or rather the lack of a little more. BS448, the valve base bible goes back to 1932 and althogh I don't have copies BSI have very kindly sent me the indexes. 1932/36 is just 4, 5 and 9 pin British bases, but 1947 does not have B8B - bue does have B9G, and B8G appears in the 1953 edition.

So B8B was never a British Standard base, not that this gets me any closer to anything. The thick plottens...

22nd Feb 2016, 2:20 pm	#1
Jeremy M0RVB Hexode Join Date: Jul 2003 Location: Leeds, West Yorkshire, UK. Posts: 458	B8B / B8G bases - difference? Hi Does anyone know the difference between a B8B and a B8G valve base? I've seen many 8-pin lock-in types listed as B8B, and I've seen both types described as loctal, but the CV datasheets for them show the base as B8G - e.g. EL22 / CV304, 3A/167M / CV5221 Is it that the B8B does not have the spigot lock? I have some developmental valves which do not, e.g. this 'prototype' KT101: http://www.tubecollector.org/e1796.htm Jeremy

23rd Feb 2016, 2:38 am	#2
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: B8B / B8G bases - difference? Hi Jeremy, I've always been aware of the B8G and B8B valve bases and like you have wondered what is the difference between the two. The B8G base was developed by Sylvania and is also to be found on valve types made by various manufactures. Valves developed by Sylvania with the B8G base are the 7S7, 7C5, 14S7 etc. The Philips valves with the B8G are the ECH21, EBL21, UCH21 etc. The Brimar 5B254M series also has the B8G base. From the Radiomuseum: Description The Philips 21- "Key Base" tubes were initially designed in 1940 with the 9-pin base B9G like the EF50. The later series production from 1942 on however was changed to the 8-pin Locktal-base B8G designed by Sylvania. So perhaps the only difference is the style of centre spigot? DFWB.

23rd Feb 2016, 2:34 pm	#4
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,397	Re: B8B / B8G bases - difference? Something rings a bell that there were even early 9-pin and later 8-pin versions of the ECH21, the later version having cathode connected to the spigot.... Calling the B9G variant "locktal-9" seems contradictory in itself. Could it be that B8B was the officially chosen designation but B8G became used colloqially because of the B9G association? I have versions of the same valve, eg KT81, W81 and so on that have both thermoset and diecast alloy bottomed incarnations- both strike me as additional manufacturing expense as the era of glass button base valves commenced. Seemingly a bit like the B8a/lockfit series in being a relatively short-lived diversion. Last edited by turretslug; 23rd Feb 2016 at 2:40 pm.

23rd Feb 2016, 6:25 pm	#5
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: B8B / B8G bases - difference? From one of the Babani books. A list of 8 and 9 pin tube bases. The B8G is shown with the centre spigot as a 9th pin. Used as the cathode connection on the E(U)CH21 triode-heptode. The base "L" is the one fitted on the Sylvania all glass 7B7, 7S7 and 7C5 tubes. We know this base also as B8G. No reference to a B8B base in the book. DFWB. Attached Thumbnails

23rd Feb 2016, 7:39 pm	#6
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: B8B / B8G bases - difference? The Quarrington book "Radio circuits and Data" refers to the loctal base as B8B and this is the base employed on the Philips/Mullard ECH21 and EF22 as well as the Sylvania developed 7S7, 7C5 etc. Also the battery output pentode, the 3D6. From the Valve Museum: http://www.r-type.org/exhib/aad0188.htm The loctal base is described as "B8B". So at least we now know there was a valve base designated as "B8B". DFWB.

24th Feb 2016, 10:27 am	#7
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,397	Re: B8B / B8G bases - difference? The BRT400's manual also refers to "B8B" types, so the designation appears to have been around at least to start with. Perhaps they were designations from opposite sides of the Atlantic for bases that were marginally different in some detail but which were interchangeable for practical purposes. I sometimes wonder if this sort of differentiation comes about for commercial/legal loophole purposes as opposed to purely technical reasons. Tsk!- I should have said "B8a/rimlock", not "B8a/lockfit" above

25th Feb 2016, 4:14 pm	#8
Jeremy M0RVB Hexode Join Date: Jul 2003 Location: Leeds, West Yorkshire, UK. Posts: 458	Re: B8B / B8G bases - difference? Well I found a little more, or rather the lack of a little more. BS448, the valve base bible goes back to 1932 and althogh I don't have copies BSI have very kindly sent me the indexes. 1932/36 is just 4, 5 and 9 pin British bases, but 1947 does not have B8B - bue does have B9G, and B8G appears in the 1953 edition. So B8B was never a British Standard base, not that this gets me any closer to anything. The thick plottens...