06-20-11: Samhar
F33 = GZ34/5AR4 B8K3= Blackburn '58 or '68 Nov third week
F31 same tube
Samhar (System | Threads | Answers | This Thread)
06-20-11: Mofimadness
Samhar, Thank you!
Mofimadness (Threads | Answers | This Thread)
06-20-11: Samhar
The F31 was made in Holland and relabeled, I'm told. Glad I could be of help.
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06-20-11: Pdreher
Samhar... that's some pretty impressive knowledge you are sporting there! How do you know that?
Pdreher (System | Threads | Answers | This Thread)
06-20-11: Samhar
I'm getting better with my keyboard, almost worthy of AA!!!!
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06-20-11: Tomcy6
A little additional info. F3 is the tube type. 1 (and 3) is the change code or version of the tube.
B91 = Blackburn, 1959, Week 1
In the early 60s they went to a 4 digit code that included a letter for the month. So,
B8K3 = Blackburn, 1968, November, week 3
If the B is etched into the tube, it was made at the Mullard Blackburn, England plant. The painted on labels were often changed. That is, a Mullard made tube could be painted with an Amperex or RCA label but the etched codes always tell you where and when a tube was actually made.
For more information just google Amperex tube codes.
Tomcy6 (Threads | Answers | This Thread)
06-20-11: Mofimadness
Tomcy6, thanks for your additional information. I found those tube code pages on the web, but still couldn't decypher them. Seeing how you used the code and what it means now makes sense...thanks again.
Mofimadness (Threads | Answers | This Thread)
06-21-11: Tomcy6
You're welcome Mofi. I have a pdf of the codes that someone cleaned up that is much easier to read and understand than the ones that are copies of old booklets. I can email it to you if you send me an email.
Tomcy6 (Threads | Answers | This Thread)
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