That is not the final schematic, this is one I drew as a starting
point and there have been many changes (including a cathode resistor
to provide some of the bias and a resistor with a few turns on it on
the plate for avoiding parasitic oscillations). It's not quite
class-c, it's somewhere between class-c and class-b by the way. The VR
valves were not used when I configured this for AM, but I am only
using CW now, so I thought the regulated screen voltage is not a
problem... Need to revisit that I guess...
73, D.
2012/12/19 Graham <[email protected]>:
> lol well that config is for linear service , you should have the
> screen fed via something like 6.8K from the plate supply , with a
> 0.1 uF decoupling cap , no regulation for class C as the screen voltage
> will vary as the anode amps / secondary emission changes [ negative
> resistance type of thing] , you need a 100 ohm 2 watt resistor ,
> shorted with a over wound 8 turn 10 mm id coil directly to the anode
> as acp , would normally have 50/100 ohms in series with the cathode
> as auto bias , should the drive fail, or IA = inf very quickly ...
> starts off with orange anodes by the wire supports , then yellow ,
> then sparks inside , then white anodes , then glass shatters / melts
> = game over , with cathode keying , looking at a big gap cw key !
>
> Happy days : )
>
>
> G..
>
> --------------------------------------------------
> From: "Dimitrios Tsifakis" <[email protected]>
> Sent: Tuesday, December 18, 2012 11:46 PM
>
> To: <[email protected]>
> Subject: Re: LF: Better picture of the 807 based 500kHz TX
>
>> 2012/12/19 Graham <[email protected]>:
>>>
>>> Why the stabilised screen supply ?
>>> G..
>>
>>
>> It's embarassing. I like the glow of VR tubes! :-)
>>
>> 73, Dimitris VK1SV
>>
>
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