[AMRadio] AM amp from 807's ? (+Rons HV Supply/Round Table)

[Bill Smith]

Bruce, I don't know what to recommend for 200-300 watts at 6-meters, perhaps
a 4-400.  Better yet, a ceramic tube.   A pair of 807's might be good as a
driver to a final.  807's really won't operate at a 200 watt power level for
very long.   I recall hearing stories when 807's were $0.25 each, of people
who would run them upside down in a pail of oil, with lots of drive and B+,
to see how much power could be developed (and how long they would last with
white-hot plates).  But don't think that is what you are thinking of..  :-)

An 829 (should be easy to find) can be run at 60 watts or so output at 6
meters.  An 807 is just a 6L6 with a plate cap, and an 829 is a pair of
6L6's in a funny glass envelope and pins so that it can run at higher
frequencies.

BTW, not all 807's are built the same.  Hope yours have ceramic insulators
supporting the plates, and a metal shield at the base of the plate assembly.
They are the good ones.  RCA in the last days made cheapies without the
shield, and with flimsy supports for the plates.   They are good for audio
applications.

You might consider a whole bunch of 807's in parallel, but doubt that
approach would be very efficient at 50 Mhz.

73 de Bill, AB6MT
billsmith at ispwest.com


----- Original Message -----
From: "Bruce - KB6LWN" <kb6lwn at qsl.net>
To: <amradio at mailman.qth.net>

>
> I realize the maxfreq of the 807 is 60 Mc, but perhaps
> with some good layout planning and some finnageling of
> lead/component dressing, and maybe some extensive tube
> and stage shielding and cooling (ala tin can chimneys)
> it can be op'd on 50.4 Mc without too many parasitics.
> Plus, I've read that if the plate/screen potentials are
> reduced to 90-95% of max, the max operating freq goes
> up just a little bit.
>
> So...  Basically, I figure we're looking at tuned input
> and output circuits, the proper matching of these stages
> to the set (2 or 4) of 807's (or 1625's), some filter
> stages to clean things up a bit, and a PS (700vdc plate,
> 300 vdc screen, both variable), and some metering, for
> an amp that I should be able to sit beside the HT-40
> on the desktop, and would provide somewhere in the area
> of a fairly clean 200-300 watts.  Anyone concurr ?
>
> > 57 degrees this morning in Shreveport Fellows. The 3880
> > crowd is on now (4:50 AM) so I gotta go
>
> Like I said...  Must have missed the above 1st time thru.
> Sorry :(
>
> > 73's and god bless
>
> Right back at ya bro...  With a Big "G" :)
>
> Bruce
>
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