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Old 3rd December 2005, 11:26 PM   #1
Devius is offline Devius  Portugal
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Default About tube codes

I have a question. This is probably too stupid and I'll be banned for life, but I've searched and couldn't find any info about it. People just seem to know.

In a Mullard or Philips or whatever tube date code, for intance D6C3, how do I know what decade it belongs to? Is it 1956? 1966? 1976? Can that information be extracted from the change code?
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Old 3rd December 2005, 11:32 PM   #2
316a is offline 316a  England
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Hi ,
A 1950's valve would have a three digit code so D6C3 would be a Valvo (Hamburg) manufactured valve , either 1966 or 1976 . What is the getter shape ? Flat dimpled disc or halo ?

cheers

316a
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Old 3rd December 2005, 11:35 PM   #3
Devius is offline Devius  Portugal
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It's a halo but the valve I used for the example is a PCH200. Does the rules apply to all types of valves?
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Old 4th December 2005, 09:22 AM   #4
316a is offline 316a  England
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Hi ,
This applies to all Philips/Mullard/Valvo etc manufactured valves . Disc getters indicate >1970 production , square getters <1959 although halo getters were used from 1960 all the way through to the end of production . Logo inking and boxes are also a good indicator of age , especially the pricing on some UK made Mullard boxes which would indicate <1971 if in pre-decimal currency . There is a list of factory codes on the Triode Electronics website which may be useful

cheers
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Old 4th December 2005, 02:38 PM   #5
Devius is offline Devius  Portugal
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Thanks a lot for the help!

I had already seen the triode electronics site when I was searching for the date code info. There are actually a few sites that have all the date codes and tube codes but they don't specify how to identify the different decades!

Just another question. I have a used EL34 with a metal base and it's date code doesn't match the one listed on the tube code list. It has a solid disc getter and according to what I've seen on the net it should be one of the first true EL34 ever made by Philips, probably 1949 or something. Considering this, how can I be sure a disc getter indicates a post-1970 valve?
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Old 4th December 2005, 02:48 PM   #6
316a is offline 316a  England
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Hi ,
The 1970's valves have a dimpled disc getter . The EL34 that you mention have a flat disc (some call it a 'foil') getter typically of early 1950's manufacture . Early 1950's codes are numeric , I do not know how to decipher . Mid-late 1950's - 1960 will have the three digit rather than four digit factory/date code . What is the code stamped into the base of the metal base EL34 ?

cheers
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Old 4th December 2005, 07:15 PM   #7
Devius is offline Devius  Portugal
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Oh!! I see!! I just have to figure out what a dimpled disc getter is I also saw some getters that were like a tiny horn. Is that a dimpled disc getter?

Quote:
Early 1950's codes are numeric , I do not know how to decipher .
I also have some Philips, and the likes, tubes that I can't seem to decode. They seem to use some other type of code because I can't make sense of them. The EL34 code looks like 5F/SYN. Take a look yourself:

EL34 Base Code
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Old 3rd September 2011, 11:29 PM   #8
Milen is offline Milen  Bulgaria
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Can I find somewhere data about all tube manufacturer codes, how do I read them?

I found this when I searched about my Mullard EL34 XF3 - EL34 / 6CA7 TUBES IN STOCK

Is there some more info about codes?
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Old 4th September 2011, 12:35 AM   #9
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The best compendium I've identified is:

http://frank.pocnet.net/other/Philip...CodeListAB.pdf

The decade issue can still be ambiguous to interpret, and can be helped by the getter identification (as above), and the printing/box, and if the valve was original with the equipment.

Ciao, Tim
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Old 4th September 2011, 01:06 AM   #10
Milen is offline Milen  Bulgaria
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Thanks, very helpful material
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