>
>Hi all, Me again...
>
>Thanks to Pete, N4ZR for a quick response!
>
>I pulled the first tube. This is the one on the left as you
>face the amp. Plugged in the 240 volts... so far so good.
>I triggered the HV interlock and... FLASH! ZAAP! BANG!
>
>There I was smelling that burnt smell again. Oh, well!
>Nothing ventured, nothing gained.
>
>I then pulled the other tube. Now, when I triggered the HV
>I'm rewarded with HV on the meter about 2200 vac in
>low and 3200 Vac in high. Looks normal, I guess.
>
>So, on to questions, part two.
>
>I looked under the amp and did not see an explosive
>destruction on the resistor/choke assembly like
>I did on tube number one. Whew!
>
>But... the arcing seemed to occur in the same place
>under the chassis on the right side.
>
? The clear and present danger in a 922 is burning bandswitch contacts.
(See real toasty bandswitch photo in "Parasitics Revisited", Sept/Oct,
1990 *QST* -- photo also on my Web site). The 922 bandswitch arcs at
5000v. The Tune C arcs at 6000v. 'Tis better by far to arc the Tune-C
and file it smooth. Arc the bandswitch and it's toast. To make sure
that the Tune C arcs at a lesser potential than the bandswitch, bend the
first rotor plate so that the Tune-C uniformly arcs at c. 4000v. I know
this sounds nuts, but 922 bandswitches are Not inexpensive and changing a
bandswitch will definitely mess up a Saturday morning.
cheers
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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