[Milsurplus] [ARC5] Solved: Where'd the Harmonic Come From?

[David Stinson]

From: J Mcvey [mailto:ac2eu at yahoo.com] 
Subject: Re: [ARC5] Solved: Where'd the Harmonic Come From?

 

> What is the pate voltage and current you need? 

Pushing the 6S4 a little.  Settled on 300 Volts plate.

6S4 is speced for 30 mA Ip, pulsed to 105 mA.

Looks like the best bias for the 6S4 PA in this circuit is about -27V

(well into Class-C.  Earlier bias was at -52!  Ouch.)

Best bias for the Modulator stage is about -17

in the current configuration.  More on all this later

 

>There is a 6as7 triode that can be had for $20 NOS.>

Looks like a good tube but once you build an adaptor, it’s too big to fit.  
Doing anything which can’t be put back original- like changing tube sockets-

is forbidden on my bench.

 

>I was also wondering if you could use a power pentode by running  a limiting resistor  to the plate for the >G2 supply and a larger than usual bypass cap at the grid ?  Hokey, but might work?

Been seriously looking into that very idea while working on affordable tubes for the BC-375.

I think we could make that work.  

 

TNX OM ES 73 DE Dave AB5S

 

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