produced after 1968.
Mostly you will find three codes on the tube.
- Two 3 digit codes on top or base of the tube like “244″.
This is the batch code and was used for warranty purposes only.
- On the side or at the front of the tube there is a 7 digit code that starts with a letter “B” or “U” and sometimes ends with a letter like “f”.
B = Berlin, Germany
U= Ulm, Germany
We only need the first 5 digits starting from the left side in order to decode the manufacture date.
Example: U5100611 = Ulm, June 15, 1970
U = Ulm
Day = Reverse the first and second digit => 15
Month = Third and fifth digit => 06 =>June
Year = fourth digit is last digit of the year => 0 => 1970
Example: B9016100 = Berlin, November 9, 1976
B = Berlin
Day = Reverse the 1st and 2nd digit => 9
Month = 3rd and 5th digit => 11 => November
Year = 4th digit is last digit of the year => 6 => 1976
Genuine Telefunken tubes like EL84, ECC83 and ECC82 etc. have a Diamond logo <> mark in the glass between the pins. The production code on the tube should be the same as on the flap of the original tube box. If this is missing then most likely it is made by Siemens or another manufacture. If you find an extra number like “1″ behind the model number on the box it means that it was made in Germany. If the tube was manufactured outside Germany it should be marked with “2″.
