>
>The 3-500z in my SB1000 seems to be getting a little tired. It seems to take
>more drive to get less grid current and output then before, and power
>seems to
>drop off as it gets warm.
>
>I'm going to open it up (the amp, not the tube) and look around. While
>I'm at it, I'm going to bring the filament pins to the back of the chassis
through a
>couple of 10k resistors so I can have a convenient place to check the voltage.
>
... good idea. Numerous owners have reported filament potentials above
the specified range of 4.75 tp 5.25 Vrms.
>My question is twofold: First, does anyone have a suggestion as to what
>to look for other than the tube?
If Pout drops when the amplifier is hot, tank component heating is more
likely the reason than a problem with the 3-500Z.
- If you are able to get 400mA of plate/anode current with 65w drive,
the tube is still good. // Note: The Eimac spec. is 400mA max. As I
understand it, there is a statement in the manual about using 500mA.
Even though such a current may be possible with over-drive, linear
amplification will not result.
- later, Vic
Rich. Measures. Web site: www.vcnet.com/measures
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