artie wrote:
In article , Andrew
VK3BFA wrote:


A subject got sidetracked a while ago, with numerous people getting
nostalgic about the boxes of old 807's they had sitting around waiting
to be used - has anyone built a HF linear using these things - and not
QRP or max 100watts - found one reference to 4 of them in // giving
250 watts - getting there , but a bit more power out, perhaps? - any
pointers to info or sites - there MUST be a use for these things, I
have been hoarding them for 30 years now!
73 de VK3BFA Andrew


The thing that immediately pops to mind about an old 807-based
push-pull parallel amp (6 tubes) was that it was a #$!!*% to
neutralize!

Cross over neutralization circuit should be simple
to set up. A six tube 807 circuit should have about
the same g-p cap as say a 2 tube 811A setup, though
a bit more output C (would be absorbed into the tank
though). Trick with 807's is to sub mount the tubes
below the chassis so the bottom of the plate
is just a hair above the chassis. This lets the chassis
serve as a shield between the plate and the grid circuits.
Millen sold a tube shield for the 807 that would do the
same thing with the socket mounted at chassis level.