[Amps] cathode to ground in tetrode amp

[Will Matney]

Jim,

That's what it's for but it don't look to be the right value. The original dwg (black dwg) looks to be a 15K 20W. Others I've seen though use a little more resistance than that if I recall. About all screen circuits I've seen will have that because of being able to have + and - current at times. Because of this same thing, a shunt regulator is better than a series like the one in the black dwg. The design in the black dwg will work though as it has been built by another ham. Below is a link to an amp using a GU-43B and it uses a 27K 10 watt with a shunt regulator. There is also two 230 Vac varistors in series to ground off the screen (safety). The screen voltage runs about +350 on this amp and is a decent setup. One thing this ham does is to use a light bulb for the shunt regulators dropping resistor.

http://www.xs4all.nl/~pa0fri/Lineairs/Frinear1500/FRI1500eng.htm

Best,

Will





*********** REPLY SEPARATOR  ***********

On 1/30/06 at 9:27 PM Jim Tonne wrote:

>Subject: Re: [Amps] [BULK]Re: [BULK]Re: cathode to ground in tetrode amp
>
>The 22 uH and 1000 pF in the grid peaks at 1 MHz and rolls off at 12 dB
>per octave after that.
>
>Can anyone tell me why they put a 12K resistor from screen to ground?
>Its on the load side of the screen current meter.  Perhaps negative screen
>current sometimes?
>
>-JT
>
>
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