I have an old (Late 60's) boat anchor 4-1000, grounded grid amplifier,
rescued form a storage building, complete with spider webs and mud dauber
nests. It was originally an 80 meter monobander. Spent a lot of time last
year getting it working.
Finally got it going on 160, 80 , and 40 meters last December. When
building the input coil, I never put a tap for 20 meters as I never thought
I would use it on 20 meters. It put out about 800 to 900 watts on 160, 80,
and 40 meters. I used it on 20 meters running it through the 40 meter
input with a tuner. About 500 watts out like that.
A month ago, I decided to change the input circuit, it is an L, so I could
add 20 meters. It hasn't worked since.
It behaves similiar to when I first tried to get it operating and the relay
to ground the center tap of the filament transformer was not working ie, no
output.
I cheked that first as the symtoms were the same.
Ohmeter between filament leg and ground, no high voltage on tube is 3.8
volts. With HV on plate it is 14 volts,with transmit relay closed
(grounding filament center tap) 0 volts, when I tried loading it with
voltmeter in this position, it arced inside of the tube so I quit.
Have tried spare tube to no avail. I have HV to plate, and I didn't touch
the output section.
I have a digital voltmete, and an antenna analyzer, and Autek, so not a lot
of test equipment.
I put a roller inductor in place of the homemade coil to see if maybe it
would make a difference. No joy there either.
I was thinking of running coax to the filament and through my MFJ tuner to
see if I can tickle it somehow.
I am stumped, and my new Double Extended Zepp for 40 meters is awaiting
some rf.
Any thoughts, ideas are appreciated.
The circuit for the thing is almost identical to the one in Joe Orrs
Handbook.
It looks so simple, and it has me totally Hypnotized.
I did this with a car one time, I changed the spark plugs and it wouldn't
run. The powder core of the coil wire was bad, and I guess from jarring it
I finished it off, but it is a sinking feeling to change the spark plugs
and kill the car.
Mike Michon
AB5XP
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