> In my 8877 home brew amp, when I turn it off about a second after I do, I
> hear a little 'tink' of a spark from the plate tank area. I traced it to
> a little spark which travels between the C2 end of the plate inductor and
> ground on the C2. It jumps about 3/8 of an inch. I suppose it has
> something to do with the collapse of the 'magical fields' in the tank
> circuit and no doubt reflects the 'Q' of the tank.
>
It sounds like the "safety choke" is defective, or perhaps missing.
Without a dc path to the chassis, when you turn off high voltage
the blocking cap will discharge into the tank. That can cause
something to arc.
That's one reason all amps need a good dc path to ground in the
tank circuit at all times.
73, Tom W8JI
w8ji@contesting.com
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|