In a message dated 97-02-24 18:28:08 EST, you write:
Two things: where can I find a (cheap?) replacement banswitch - directly
from Alpha or is there any other source? And also, why does this keep
happening?
>>
I don't know about the source, you might look at the switch and see who
manufactures the switch. Most manufacturers have reasonable prices, and
you can get the right one for a few bucks more than the wrong switch.
The arc generally happens because the PA is loaded it too lightly for the
amount of peak drive. This can be due to multiple causes.
1.) Exciter transcients or overshoot
2.) Improper (too light) loading
3.) Antenna system arcs or loose connections
The tube is a time varying resistance that gives the tank a "pull". It can
not
push energy into the tank, it only "pulls on" or loads the tank.
This makes the tank voltage swing much like yanking on a rope to
pull a flywheel. If the load is removed or is not heavy enough, the
rope becomes "slack" except for a quick jerk when the tube turns on,
and tank voltage will climb to VERY high values. Voltage and stored energy
will build until something extracts the energy from the tank.
In your case it was the switch.
Things that cause a switch to break down in PROPER operation:
1.) Sharp points on the high voltage contacts or wiring
2.) The ten meter tap being located adjacent to a lower voltage terminal or
grounded point.
The voltage is highest at the anode, and decreases towards the load. NEVER
put the ten meter tap (the highest voltage tap) next to a lower voltage tap
(like 40 or 80 meters).
73 Tom
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