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This listing is for a Pair (2) of 84 Full-Wave Rectifier 6Z4 Antique vacuum tubes in the ST (Coke Bottle) tube shape. They have a black 5-pin UY base, Black plate, and bottom D getter. Labels in stock include RCA, Sylvania, Tung-Sol, Philco. If you're looking for a particular brand, please message right as you order - we pack and ship quickly!
Some have engraved bases.
Your tubes have been fully tested on our Knight 600A tube tester with like new, NOS results (tNOS). Here's what that means: to qualify for this listing, several stringent conditions must be met: the emissions for both sections must test within between 80% and 120% of bogey values, consistent with original 1933 RCA, Sylvania, GE, and/or Tung-Sol datasheet specifications for new tubes of this type. The tubes must also show no shorts. The tubes might have mechanical wear or have the label rubbed off - these are very old! Unbalanced and used-testing tubes are available in a separate listing at a significant discount. Every tube you receive from Sound By Doc is guaranteed against failure for 60 days after purchase, an industry extreme!
OPTIONS:
Want a regular white box? $1 extra
Comfortable with a tube that has tape at the base? Save $1
Most of our tubes are tested with one of our Amplitrex AT1000 tube testers, but these fantastic testers do not have built-in support for this tube type. Therefore, this type is tested on our Knight 600A tube tester from 1969. Most vintage testers use a proportional emissions test at 30VAC and extrapolate to real, working voltages, but not this one! The Knight tester is revered for its 250VAC, real-world emissions test and for its robust gas test. Since we have not calibrated your tester, we cannot guarantee that the test results on your tester will be the same.
