G'day Bill,
I've got the same problem with my 2 x 3-500Z homebrew amp.
It is my spare amp. I put a new 10 -20m tank coil in and it is now
misbehaving in the same way as yours.
When I tune up on 10m, I get arcing on the 160m position on the bandswitch
to the frame of the switch. This position switches in the 160m padding
capacitor. Nothing in the 160m circuit is connected when it's on 10m. The
tubes also get extra warm in the 10m position.
I was thinking of getting one of the AG6K suppressor kits to see if that
changed things. I probably will anyway, just for insurance.
73 de Alek, VK6APK.
At 04:07 PM 07/30/1999 -0700, you wrote:
>
>Ladies and Gentleman:
>
>The saga continues with my amplifier recently purchase Amp Supply LK500-ZA.
>I received a very helpful response from a member in this group familiar
>with the amp and I have decided to replace the padding capacitors in the
>tank circuit.
>
>As I mentioned in the 1st post, one of the 160 meter padding caps was
>fried/burnt which is located on the Load side of the PI circuit. I also
>mentioned that the previous owner mentioned that when operating on 10
>meters he smelled something burning. I did not believe that the particular
>160 meter capacitor that showed signs of burning was related to the 10
>meter problem since the capacitor was not physically connected when
>switched to the 10 meter position.
>
>So I connected a dummy load and transceiver to the amp and plugged it in
>and tuned it up on 10. After getting a good match I left it key down for a
>few seconds and sure enough I WAS WRONG. The 160 meter capacitor started
>smoking
>
>I am at a loss for an explanation on this one. When switched to 10
>meters/AUX, the 160 meter capacitor in question is out of the circuit. I
>checked the bandswitch wafer(s) and there is not a short or problem,
>everything checked out like it should have (or at least I think).
>
>The 160 capacitor is connected to a beefy wire that is connected between
>the wafer and a side wall. This lead is long and goes across the top of the
>variable Load capacitor in the PI/Tank circuit. I might also mention that
>the tube is running much hotter at 10 than on the other bands, the outer
>case above the tube is uncomfortably hot.
>
>My only guess/explanation is that there some type of coupling going on and
>the only way this could happen is at a very high frequency. Did I inhale
>too much of the burning capacitor? I feel like changing my call to
>kr6ack!!!
>
>73s
>
>Bill, w6qd
>
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