[AMPS] Re:Question: input Z on class AB gnd grid pair 4-400 ??

[Steve Bookout]

OK, Larry, nothing like a little real experience to put things in
perspective.  I never tried it that way, but always read that it was not
the way to go.  (Maybe written by those who wanted to cover their butts.)

It's absolutely amazing what those tubes can take.  I bought 4 in '81 for
$10 a piece from a local FM station engineer.  They were nasty looking
things.  When first used, I got 1200 watts out and now I get 1200 watts out
(of a pair.)  Done all types of mis tuning, etc. and they have always
forgiven me.
Had one plate strap break once in a contest and when I noticed it, the
other tube was almost incandesent!.  Fixed the strap and kept on
contesting, with no harm done.

Thanks for your input.

73 de Steve, NR4M


>
>Steve,
>
>That's just what I thought some years ago. since I saw so many cross-cooled
>amps being built, I decided to de-bunk that idea myself. I built a
>mono-band amp with a pair of 4-400A's. Put the sockets on a little raised
>plate with about 3/4 inch clearance between it and the chassis. Mounted the
>muffin fan about 4 inches away from the tubes.
>
>The amp runs 1500 out all day, every day, CW, RTTY contests, even (ugh)
>SSB. Tune ups are done full power locked key. The tubes seems to be fine.
>The pins have not unsoldered, the socket springs have not turned to mush,
>still full output. This particular experiment has only been running for
>about 13 years, so I guess the tubes could still fail!
>
>I am not saying this is a better way, just that it appears to be a viable
>alternative even for 4-400 type tubes.
>
>73,
>
>Larry - W7IUV

---------------------------------------------
Steve Bookout, NR4M (ex NJ4F)
Rapidan Data Systems

'DX4WIN...The way logging programs should be!'
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