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.
Am I going to have to invest in new tubes to further troubleshoot
this thing? How can I test the tubes? I'd like to narrow it down a
bit more, although it seems like I'm on the right track, thanks to Pete!
Now what? Is there a possibility that all this banging and arcing has
caused additional damage?
Looking at the schematic, I see that the assembly in question is on pin 4
on the left and pin 2 on the right. These must be reversed, since they both
appear to be on the grid of the tube.
Testing with my V/OM, I can see continuity between the two pins
that appear to feed the heater, and the three pins that are connected
to the grid. My meter cannot see a connection between the grid pins
on the bottom and the plate connection at the top. I'm assuming that
some kind of HI-POT test is needed there.
So... back to the testing. How can I test the tubes/amp to see which
is the culprit? It appears that the tubes are causing a problem, because
the HV is on when they are missing. Would it buy me anything to test them
plugged into the socket, but with the plate not connected? Especially
remembering that I really don't wish to have a melt-down here...HI
Thanks again!
Gary, WG7X
----- Original Message -----
> First, I'd try pulling the tube out of that socket, and powering the amp
up
> with just one. That would tell you for sure if it's just a shorted tube
> element, which is what it sounds like.
>
> 73, Pete Smith N4ZR
>
>
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