Reading Ei/Yugo date codes?

[greiswig]

Hi,

Does anyone have the secret decoder ring for date code for Ei power tubes? This is what I can make out:

B3B
03K (where 0 is the circle with a dot in the center)

Thanks muchly!![/code]

[David Root]

It's either '83 or '93 The K is the month, maybe Sept or Oct. If you're lucky it's '83. Do you have a pic?

The O with dot in the middle is for the EI factory in Nis, Yugoslavia (as it then was). Next digit is the year, third digit the month. Unfortunately it's ambiguous as to year, sort of like the EIA date codes from the '50s and '60s.

The other three digits might eliminate the that ambiguity but I don't have that part of the decoder ring. So it depends on what the tube looks like.

[greiswig]

Thanks, David. I don't have any pics. They are some KT-90s I am thinking about buying. I had heard that QC went south a few years before the Bosnian war, so if they're '93s it would sure be nice to know.

What can you identify from a picture that would place them in the right decade? E.g. "chewing gum on the plate probably means a '93."

[David Root]

There is a European site that has detailed pix of tubes from several Euro manufacturers, including EI Nis. I will have to look it up.

[David Root]

Here's a pic from that site. You can see the date code O8A, presumably 1988. I have one similar labeled for National, O0? "Made in Yugoslavia", presumably 1990.

[greiswig]

Here's a pic from that site. You can see the date code O8A, presumably 1988. I have one similar labeled for National, O0? "Made in Yugoslavia", presumably 1990.

Thank you, David. I wonder what a '98 production code would look like, then? Almost looks like they didn't plan on making tubes for very long.

[David Root]

Probably would look sloppier, they were going downhill then, QA went into the toilette in the early 2000s and they went out of business several years ago.

Old '60s Sovietski copies of Telefunken tooling, not properly maintained, could not hold tolerances, started cheapening up on metallurgy and vacuum too. Late '70s were very good, '80s almost as good.

Sort of like what happened to Jaguar cars in the '80s before Ford bought them. (You had to be there! I used to own a '95 Jag XJ, Ford done it right)!