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My friends in the Asylum:I need some help please. I have four Valvo ECC82 tubes with the following codes:
GFO D9L , GFO D0I, K62 D7H, and K62 D9H. I am a neophyte when it comes to the codes on European tubes, so any help translating these codes would be appreciated. Can it be told when these were manufactured? They have the angled getter that is round.
Follow Ups:
My thanks to all who replied here. The information is most helpful and also most appreciated. I am always amazed at the number of folks who have such an intricate knowledge of the tubes and codes on such a variety of brands! Again to all who responded, my thanks!
Check the link for info on Mullard 12AU7's. The info is mostly valid for Valvo's as well. Cheers Steve
BJ- These are all 12AU7s made in the Philips-owned Valvo plant in Hamburg, Germany. The k62 specimens are older, and will be found to have longer (17mm) grey plates. D7H = Aug 1957 manufacture, D9H = Aug '59.The Gf0 pieces are early shorter (15mm) plate version that superceded the longplate. D9L = Dec '59, D0I = Sept 1960. All of these had the angled halos, attached at the edge without a separate support rod. The "D" in all the above cases is the Hamburg factory code. As you can see, 1959 was the transition year for these two types at Hamburg, just as was the case for their 12AX7s. There seems to have been less "overlap" there compared to some other Philips factories like Blackburn, where longplates and shortplates were made simultaneously for many months.
I'm really a fan of the Hamburg 12AX7s, suspect the AU7s are excellent too.
The way it works is like this.The top line, k62, stands for the tube type, k6=ECC82, and the 2 is the is the change code=minor changes in tube.
The second line is the plant where it was made and the year/month.
D=Valvo, Hamburg. The 9 we have to assume means 1959 as before the mid 50's they only had 2 character codes and I doubt it was made in 1969. The L=December. Jan. is A, Feb. is B and so on.The problem is GF dosen't equal ecc82 but instead indicates a CV131 which is a pentode. So look again and understand capitol letters matter and sometimes it is a symbol and not a letter. Also the 12au7 was offered under about 20 different numbers which makes it even harder.
Brent Jessee's web site has a link to tube codes and a short article on how to decipher. Perhaps someone else will have a better guess on what the first two tube codes relate to. Does the tube have any other number on it besides ecc82? Maybe a CVxxxx number or a Mxxxx.
Russ' info is good, except . . . you'll find the type code on the shortplates is actually Gf0, not GF0, these are case sensitive! Gf is indeed 12AU7. In fact, you'll find it on Philips 12AU7s from other plants, but these will have different factory code, like the "delta" for Heerlen, etc., rather than the Hamburg "D".Also, the dates given above are the only ones that fit the data provided; there were no Hamburg k62s other than in the 1950s, etc.
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