[R-390] Russki 6AK5W equivs on E-bay

[Tim Shoppa]

I bought a bunch of Russki "6AK5W/5749"'s on E-bay for twelve cents each.

The tube number in quotes because the tubes don't even have cyrllic
markings that I can decipher. They certainly aren't "real" 6AK5W's -
way too tall (like 2", even taller than a 6BA6 and at least half an inch
taller than real 6AK5's) to the point where
if I stick one in my 390A's crystal oscillator, I can no longer put
the lid on the 390A!

The seller is British but the tubes actually ship from Ukraine.
No indication on the auction that these aren't real tubes or that
they're Russki tubes, but hey, I guess I should've known better than 
to buy from an auction that states repeatedly in the title and body 
that these are 6AK5W's/5749's.

They do seem to mostly work when I stick them in and in fact the
S-meter readings go up very slightly. My guess is that the operating
point of these Russki pentodes is different than a real 6AK5W.

Casting about on the websites I have not seen any details about
Russki 6AK5 equivalents. Physically what I can see inside looks
more like a 6AU6 with the 7BD (instead of 7BK) base. (Not that
those bases are very different anyway.)

Oh, well, I've no shortage of real JAN 5749's, so it's just a
(monetarily cheap) lesson learned. I've had a lot of fun reliving
my childhood and getting tubes on E-bay that seem to be in every
way identical to the ones stacked up at hamfests from when I was
a kid but I could barely afford at the time, and I'm not going to 
stop because of one rotten apple :-).

Tim.