[AMPS] SB-220 Idling Current

[Rich Measures]

>WA4VWR just bought a pair of Eimac 3-500Zs (found them in Washington
>state) to replace the pair that he had been running since 1974.  Much
>to his amazement, when he plugged them in and fired them up, they
>drew only 140 ma of resting plate current instead of the usual 190 ma
>of plate current that he was use to seeing.

There are counterfeit Eimac stamps.  My guess is that he bought some 
higher Mu tubes that were not made by Eimac, which were de-inked with 
acetone and restamped with a counterfeit stamp.  . . . . To put the zero 
signal anode current in the linear range, try shorting out the 5v zener.  
>
Rich---

R. L. Measures, 805-386-3734, AG6K   


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