Where to find modern tube data sheets

[Paul P]

I've been trying to find the datasheets for modern (Russian) tubes and
can't find them anywhere. I have an RCA manual, RC-30, but I don't
know how well new tubes fit these old specifications.

One example of why I would like to see the specs is that I see 6v6's
in Fender schematics with 415v on the plates when the RCA manual
says a maximum of 350v.

How does one decide what the limit is ?

Thanks.

[Steve Conner]

Well, if a Russian tube is sold as a replacement for an original US or European type, it should of course meet or exceed the specs of the original type. For Russian made "reissues" of old tubes, like the Tung-Sol 6550, you would expect the original datasheet curves and limits to apply.

If by "modern Russian tubes" you mean the likes of the 6Pi3S and 6Pi3S-E, then the Russians probably don't want you to see the original datasheets, in case you figured out that they are rebrands of existing Russian tubes, and only bear a passing resemblance to 6V6s, 6L6s or 5881s. Nevertheless, the 6Pi3S-E (sold as the Sovtek 5881 or 5881WXT) seems to be a great tube, Fender switched to it for all their new amps.

http://www.tubes.ru/techinfo/HiFiAudio/6p3s.html
http://shmeurg.free.fr/6p3s_datasheet_fr-376.jpg

Note that they only specify them up to a plate voltage of 250V! I've tested both types in a push-pull amp up to 475V B+ though, and other members here have abused them even worse...

Maximum plate voltage is a pretty vague limit and you can often get away with exceeding it quite a lot. Electrode dissipations are a bit less negotiable, running too hot will always shorten tube life.

[Paul P]

Well, if a Russian tube is sold as a replacement for an original US or European type, it should of course meet or exceed the specs of the original type.

This is reassuring. I've read that some new tubes can handle higher
voltages than the originals so I was wondering (if it's true) just what
the new specs might be. I find it odd that the companies manufacturing
tubes don't post the specs for them.

I wanted to compare different tubes before buying them but it looks like
that won't be possible. Also I've been studying Crowhurst et al, and would
have liked some real-life examples to practice on while designing my amp.

I have a high voltage power supply with both B+ and C+ supplies so I could
make my own charts but determining maximum values would be difficult.
And my supply only goes to 400v which isn't enough for power tubes.

Paul P