[R-390] Done to death, delete at will: 6DC6 surrogates

[Jordan]

Seeing as the 390 was 'stealth' type equipment, was there not something in the
archives about EMP ratings for this tube..??? I know there is a document that details
the developement of this tube specifically for the 390A... 73 de Jordan..

David Wise wrote:

> I picked the word "surrogate" with care.  These are not
> substitutes.  They are enough to keep you on the air
> while you look for a 6DC6.
>
> For reference:
>
> 6DC6 (5500, 12.5V=50umho)
>
> RC-29 is inconsistent about cutoff ratings,
> some are at various currents, others at
> various transconductances.
>
> A couple of these are from memory.  Others
> don't have any cutoff data.  Except for the 6AS6,
> I didn't check max ratings.  Remember, it's
> temporary and who cares if you burn it up.
> A lot of these are TV tubes, so if you have
> a box of pulls, odds are you have a few.
> Some of these didn't exist in 1952; I bet
> they'd have picked the 6GM6 or 6DE6
> for example.
>
> Out of the list below, I tried a very weak 6BZ6,
> a 6EW6, and a 6HZ6.  All worked, but of course
> not as well as the real thing.  I didn't check
> sensitivity, IP3, cross-modulation, or what-have-you.
> Don't expect the same carrier readings in any case,
> because the AGC is different.
>
> I worried about oscillation with the 6EW6,
> but I didn't see any.
>
> 7CM pinout (same as 6DC6):
>
> 6AS6 (way over max ratings)
> 6BH6 (low gm, too sharp)
> 6BJ6 (low gm, too remote)
> 6BZ6 (8000, 19V=50umho.  Runner-up to 6DC6 in Cost Reduction Report.)
> 6CB6 (8000, 6.5V=20uA)
> 6CF6 same as 6CB6
> 6DE6 (8000, 9V=20uA)
> 6DK6 (9800, 6.5V=20uA.  Used in large numbers in Tek 500-series scopes.)
> 8136 same as 6DK6
> 6EW6 (14000, 3.5V=20uA)
> 6GM6 (13000, 15V=60umho)
> 6JH6 (8000, 19V=50umho)
> 6JK6 (15000)
>
> 7EN pinout (same except internal shield connected to cathode instead of G3):
>
> 6DT6
> 6GX6
> 6GY6
> 6HZ6
>
> These tubes are designed so G3 can be used as a second control grid.  All
> have lower gm than the 6DC6.  I didn't write down their cutoffs.  I think they're
> all sharp.
>
> Some RF decks have pins 2 and 7 wired together.  These decks
> can also use a slew of tubes with the 7BK pinout, which includes
> 6AH6, 6AG5, 6BA6, and 6BC5, and another pinout I forget which,
> which is like 7BK but with K and G3 swapped.
>
> 73,
> Dave Wise
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