Re: Problem with a Fisher 400

in article C00245C0.6F9B4%jono_1@xxxxxxxxxxxxx, Jon Yaeger at
jono_1@xxxxxxxxxxxxx wrote on 1/29/06 10:13 AM:

> in article 1138519927.923593.206150@xxxxxxxxxxxxxxxxxxxxxxxxxxxx, fourkids
> at dearly@xxxxxxxxxxxx wrote on 1/29/06 2:32 AM:
>
>> 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
>>
>
>
>
> Sounds like you've got a bad tube. Swap it in another position and see if
> is still too low.
>
> Tubes are supposed to run very hot. But not so hot that the plates glow
> dull orange. Look at them in a darkened room.
>
> Note that most Realistic tubes - which were made by other companies and
> banded Realistic - have a lifetime warranty, which they still honor!
>


PS - I forgot to ask . . . . How dies it sound??

.

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