Neutralize
Carl
KM1H
----- Original Message -----
From: "pfizenmayer" <pfizenmayer2@q.com>
To: <amps@contesting.com>
Sent: Saturday, November 06, 2010 1:25 PM
Subject: Re: [Amps] Ameritron AL-572
>I have been trying to help a fellow ham get an AL-572 tamed down via
>emails.
>
> He had a tube short/arc and blow one of the 50 ohms to ground grid
> resistors- the tubes were pretty old and tired anyhow so he bought a
> matched
> set of 4 572b's from RF Parts.
>
> Replaced the grid resistor - carefully checked all the others and also
> checked all the parasitic choke elements (it has the 4 separate chokes in
> the assembly with the 2 durmica series caps in each resistor leg - all
> components are good )
>
> It is working "OK" on all bands but 15 meters - but on 15 it wants to take
> off .(Whether its VHF or around 21 mhz I dunno) He has not yet tried to
> re-neutralize. He can get it "operational" by a fairly large change in
> loading to stop arcing/spitting and at that point its about a 500 watt
> amp.
> Other bands are an easy KW - (maybe a tad too easy on 10 which makes me
> think its a littel regenerative on 10 and re-neut may be a help)
>
> I have read , think , all of W8JI's stuff on the AL572 and AL-811 amps
> and
> not sure of when he said what with respect to directly grounding the grids
> .
>
> So other than re-neutralizing , what is the current thinking of directly
> grounding the grids ? Anyone know what they are doing as shipped today ?
> He
> is going to add the gas discharge on the filaments just as a precaution to
> protect his K3 driver, and could easily do the grid grounding at that time
> ?
>
> What say Ye ?
>
> 73 de Hank K7HP
>
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