In my experience with same tube, When plate getting red with small fraction
of plate current ma, probably something wrong with tube cathode bias, make
sure cathode bias working properly.
de Firson - yd1bih
>From: Charles W BWW Burkhardt <cburk001@juno.com>
>To: amps@contesting.com
>Subject: [AMPS] 3-500Z
To: <amps@contesting.com>
>Date: Sat, 17 Mar 2001 10:53:16 -0600
>
>
>Gentlemen: Trouble with my Heath SB-100, which has a 3-500Z tube.
>By mistuning the unit I took out a couple of resisters and the grid
>current meter in the meter circuit board. Have replaced the bad
>components, and the unit tunes up OK, but when I try to drive it for just
>short periods of time on CW, with a plate current of just 100 ma, the
>plate gets bright red, and if I key just a bit longer there are bright
>blue and white flashes in the tube, followed often by blown fuses. I
>would like someone to tell me it's not the tube, but something else I can
>repair-a remote chance I suppose. Any suggestions.? TIA Charlie. K0GPF
>
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