I acquired a big lot of Sylvania 12AU7 A8V tubes with date codes 57 05 22 and 68 12 42. The former is a short gray ladder plate, latter is long gray ladder plate. Both are green logo in block letters. I have Googled and come up empty on these particular tubes.
The Sylvania EIA code is 502. The date code is 752, or 1967, the 52nd week.
The 614 EIA code is for Simpson Electric. The date code is 822, or 1968, the 22nd week.
The 614 EIA code is for Simpson Electric. The date code is 822, or 1968, the 22nd week.
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Oh, so the codes read vertically, not horizontally. That's the first I've seen that fact pointed out in any of the info I've read through, thank you!!!! Never even occurred to me to think of it vertically, lol! Is that more common than not with tube codes, or is it a pretty even split between horizontal and vertical?
Probably just depends on the space available on the glass envelope.
Larger tubes seem to have the numbers horizontally.
Larger tubes seem to have the numbers horizontally.