On my homebrew KW, I built in an interlock on the door that is
opened for access to the plug-in coils, since these run with full
modulated HV on them when the transmitter is operating. I would
never try to change coils with the rig in TX position. The more
redundancy the better. When I change coils, the interlock is
turned off, the rig is in standby position, the main HV toggle
switch is in the "off" position, and I have made it a habit to
observe the plate voltage meter to make sure it is at zero. A
shorting stick would'nt be a bad idea, either.
Don k4kyv
Don
Not only is a shorting stick not a bad idea, not using one is a
terrible idea. As someone who has spent many hours working on high
power transmitters, I would NEVER touch anything inside a transmitter
without first touching it with a shorting stick. When I do not have
a proper shorting stick available, I connect a grounded wire to a
well insulated screw driver and use that as a makeshift shorting
stick. There is are no allowable exceptions to the shorting stick
rule, as far as I am concerned.
Never rely on meters, pilot lamps or switch positions to tell you if
HV is present. Switches can short and pilot lights can burn out.
I've seen at least one high power uplink amplifier where the
designers used the bleeder resistor as part of the meter multiplier
string. An open bleeder meant zero HV on the meter but possibly a
full charge on the filter caps. In that situation a shorting stick
could be the difference between life and death. Never, ever, touch
anything inside of a high power transmitter without using a stick.
Period!
Alan
WA2DZL
- Re: [AMRadio] Stock or modify? BC rig "value"... Alan Cohen
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