Greetings to all...I'm trying to get this amp to behave but it seems to
be a T.G.T.P oscillator. Without drive at about 4KV grid and plate
current start to flow. The amp is a 20m monoband with vacuum tune and
load caps. Makes no difference what type or variation of parasitic
suppressor is used...copper/silver or nichrome. I get a dip at 62Mhz at
the plate blocking cap. The grids and screens are grounded with .25"
copper strap thru the sockets directly to the chassis. The filaments
are in series with a 15VCT transformer, bypassed with .01 micas. Bias is
provided by 4 series 1N5402 diodes. With any type of tuned input,
parallel C/L, pi, or T-input I have an oscillation. Feeding the filament
direct thru a .01 mica....no oscillation, no Ip/Ig without drive. Does
any tuned input have to be in a shielded enclosure under the chassis? Do
I necessary have an input/output feedback problem? Any help appreciated
guys...
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