Re: Problem with a Fisher 400

Well, I hope you guys are still out there....

I have added the 10 ohm resistors...happened to have 4 precision 10
ohms laying around.

And it turned out that the 5.6k ohm resistor I referenced earlier had
already been doubled, so I modified it again for a theoretical value of
1.3k ohm. This brought my bias voltage down to -20.5 volts, measured
at each tube.

The voltage over the 10 ohms is .25 to .26, except for one tube: which
measures .1 volts...I appear to have a bad tube?

OK so my problem: the tubes are still running WAY hot...they are very
hot in just a couple of minutes. Now maybe I don't understand how hot
they are supposed to be, but i have nothing to compare it to.

I have already ordered a new quad of 7868EH tubes...should get them in
a couple of days. The tubes that are in the set now are all
"Realistic" tubes...not the greatest brand, and probably all bad having
been run hot for some time.

Anyway, any further wisdom would be greately appreciated.

Dave Early
Colorado

.

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