my two hole alpha is sick, and i am looking for answers. one day it was
working fine (about 600 watts out low tap) the next week, not so good! if
say i tune it up on 7.1 mhz apply drive, plt runs 600 mills. but i get no
indication of grid current. plt voltage is approx. 1600 volts. this gives an
input of about 900+ watts input. but my output is only about 170 watts out
keydown! (yes, the 8874 tubes have been changed). if i key the amp with NO
DRIVE i get an indication of approx. 8-9 ma on the grid meter. this appears
to be the zener current of the 5.1 volt zener (1N4733) used for amp bias.
(for those who are familiar 76a, it's the current thru R-116 10 ohm 1/2watt)
the problem seems to be on all bands. the orig. set of tubes had very few
hours on them, as the amp had been unused,stored (i had a rfi problem) until
early 1999. so far in checking, i have not found any obvious indications of
parts failure or bad solder connections. any input will be appreciated.
73 hank
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