At the risk of starting another long thread, I will ask a question.
Given the relative low accuracy of normal AC panel meters, how can you be
sure that you are actually within the filament voltage tolerance specified
by the manufacturer? A high accuracy AC meter is a rather large and
somewhat expensive animal.
David
KC2JD/4
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On
> Behalf Of Nelson Wittstock
> Sent: Sunday, January 28, 2007 2:36 PM
> To: Amps@contesting.com
> Subject: [Amps] 8877 Longetivity
>
>
> FWIW I am using an 8877 in my amp that I built back in 1977. It
> is still the
> original tube. My filament transformer is run off a Variac and I have a
> panel meter to monitor and see that it is five volts. I also have a timer
> interlock so that the HV cannot be turned on until the tube has had three
> minutes to warm up. When I shut down I run the Variac back down
> to zero and
> leave the blower on for a few minutes for cool down. The amp was
> built from
> a QST article in the September 1971 issue. It has seen a lot if use. I
> added 160 meters to it and it has served me well.
>
> Nelson, K8DJC
>
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