I also had the same problem with a GS35 amp on six meters, As some one else
stated it had a bad vacuum vairable.
K6KWQ Dick
Amps by "MORE POWER"
----- Original Message -----
From: "robert briggs" <vk3zl@bigpond.com>
To: <amps@contesting.com>
Sent: Saturday, April 11, 2009 7:09 PM
Subject: [Amps] New GS-35B amplifier..
>
> Hi all....I have just completed a new single band 160 meter GS-35B
> amplifier...After troubleshooting a minor bias problem I put some RF
> into it this morning....Sadly I seem to have a problem which I have been
> unable to resolve as yet....The HT supply is 3300volts using a new
> AL-80B Power transformer....All this is operating normally....
> Variable bias controlled from the front panel gives me a range from
> nearly zero to 250ma.....This is also operating normally and for testing
> purposes I have set idling current at 90ma......
>
> Applying 20 watts of drive the amplifier tunes and loads properly grid
> current loading down to around 60ma anode current to around 200ma...If I
> increase the drive beyond 20 watts the anode current immediately shoots
> to 800ma and the grid current off the scale tripping the protection
> circuit....Power also drops to zero prior to the fault condition..
>
> I have thoroughly checked all the components in the pi network and all
> appears fine.....
>
> I am wondering if I have a bad tube or is something else breaking down
> in the output network somewhere...Maybe someone may have some ideas....
>
> Happy Easter all........Bob VK3ZL....
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>
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