Mullard Tube Code Help

F33 = GZ34/5AR4 B8K3= Blackburn '58 or '68 Nov third week

F31 same tube

Samhar, Thank you!

The F31 was made in Holland and relabeled, I'm told. Glad I could be of help.

Samhar... that's some pretty impressive knowledge you are sporting there! How do you know that?

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.

I'm getting better with my keyboard, almost worthy of AA!!!!

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.

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.