Help with mullard tube markings

[Philv]

Hi can anyone make head or tail out of he follwing markings ?-

Front -

Mullard m8137

made in great britain

Back -

UA

Cv4004

kb/dc

641

(Square with diagonal line) 230

The sites i look at dont seem to help that much or are ambigous to me.

also are these test results good? -

1.4/1.4ma

1.5/1.5ma

(tested on a funke w19s)

cheers to any mullard expert who can help

cheers

 

[Guest]

Cv4004 is just another ID for the M8137 CV 492. Ect

Kb/dc is the factory code

Those test measurements are pretty meaningless in isolation you need more detail really

I'm sure VB will be along soon with the exact factory codes,

 

[Valvebloke]

The M8137 signifies that this is a special quality version of the ECC83/12AX7 double triode. The datasheet here http://www.r-type.org/pdfs/m8137.pdf tells you all the ways in which it was special.

Made in Great Britain sounds like it should be self-explanatory. But the word 'made' is open to interpretation. It's not unknown for individual electrode components or even whole electrode assemblies to be fabricated in one plant and then sealed into the glass envelope and evacuated in another. I believe (but I'm not sure) that any indications of where the thing was made usually refer to the place where the final processing was done.

The CV4004 code is the 'common valve' code for the M8137. The UK government liked to source its valves from multiple suppliers and when it did it got them all to stamp the same code on valves of the same type. This saved engineers who, in wars, were often working under a good deal of stress from having to wade through enormous 'equivalents' tables.

641 is the type code - 64 tells you it's an M8137/CV4004 and the 1 tells you it's batch 1 of that type.

The square with the diagonal line tells you it was made in the Mullard 'Whyteleafe A' factory which was in, er, Whyteleafe http://en.wikipedia.org/wiki/Whyteleafe.

230 is the date code. The 2 tells you it was 19x2 (1952 or 1962 probably - with a bit more detective work you could find out the production dates and nail this if you really care). Normally the next character would be a letter signifying the month - A to L for Jan to Dec. The one after that would be the week in that month - 1-5. However there are examples of the Whyteleafe plant coding just the week of the year and yours looks like one of these i.e. it was made in week 30.

The best explanation of the Type/Batch/Factory/Date codes that I know of is this one http://frank.pocnet.net/other/Philips/PhilipsCodeListAB-v8.pdf.

I've never bothered to find out what UA and kb/dc mean. They may well be some sort of further production and/or date coding.

You'll need to track down the manual for the Funke tester to know whether the numbers you've measured fall within spec. They do at least look nice and closely matched.

VB

 

[Jazid]

Ecc83 tube, Military designation.

KB is UK approval to mil spec, DC is the factory where it was made - Mullard Whyteleafe

641 is a model number -these changed a bit through the ECC83 life cycle but I suspect is 64 type 1 (an M8137 code). Square thing with diagonal line is the Whyteleafe symbol then probably 2B0 which is date, but I can't tell you which year from this (others might)

If measured with standard conditions on a functioning machine the minimum spec for the ECC83 is 1.2mA emmissions, and 1.6mA/V Gm per section. If this is two tubes then they would appear to have similar and strong emmissions on each section - what the Gm is like is another matter but they appear to look quite strong. Here be bears, so no guarantees! If its eBay then check his record carefully!

 

[Philv]

Thank you for the info.

More web searching to be done i guess.

 

[Valvebloke]

... I'm sure VB will be along soon with the exact factory codes,

well, some of them, and James has supplied some others. I live and learn ...

VB

 

[Philv]

Cheers

i really dont want to use eBay!

but the resident valve sellers dont have what i want :-(

 

[Valvebloke]

Cheersi really dont want to use eBay!

but the resident valve sellers dont have what i want :-(

Langrex have 40 CV4004s and a couple of hundred M8137s showing in stock http://www.langrex.co.uk/stocklist.html. You could give them a call. I have no connection with them but when I've bought there my experience of the quality has always been good. They have an eBay shop and are listing a pair there. It might be worth contacting them directly though if you want to discuss pricing. They're a business so don't forget the VAT and P&P.

EDIT: It seems Wi Wi have them too http://www.wiwitubes.com/en/product.php?ptype=5&keyword=M8137&search=model.

VB

 

[Philv]

Oooh - they have 400 for 40k on eBay

but they ate the 80s version

otherwise i might have remortgaged