I am repairing an amp that was from a friend's estate and have fixed
several issues, but now when I switch the amp to Operate, considerable heat
is coming out of the exhaust, so it appears the tube is partially biased on
all the time. I have loaded the amp many times up to about 1kw output, so
I am reasonably confident that the tube is OK.
According to the manual, the cutoff voltage is supposed to be -130v, but
with 70vac on the primary into a half wave bridge, I cannot understand
where they are getting -130v from. My bias voltage is only -80v in RX. I
get up to -95v with the bridge unloaded, which is close to what would be
expected from a half wave bridge. The screen voltage supply appears to be
functioning normally.
I will admit, I am not much of a tech, but I DO know how to work around
high voltage and avoid exposed plate voltage unless absolutely
necessary. I have gotten this far, and would love to get this amp running
if anyone has experience with this amp and does not mind helping me sort
this out. I have more history and measurements, but I will spare the list.
Thanks,
73, Robert KR7O/YB2ARO, DM07ba/OI52ee (ex. N7STU)
DXCC 6M #1122
WAZ 6M #112
VUCC 6M, 2M
www.vhfdx.com (KR7O/YB2ARO pages)
Looking for old VHF QSL cards and logbooks.
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