[AMPS] SB220 Grid current

[Rich Measures]

>Help,
>	The grid current meter on my SB220 is all the way to the right
>with key down, even on SSB mode of the exciter.  On dekey the meter pegs
>the left side.  Is this a tube problem or meter circuit problem.   
>Suggestions please.
>
>	Thanks,
>	John 
>	KO4A@juno.com
I suspect that R1 [0.82 ohm] is open.  Reverse grid current is an 
indication that the filament may be out of line and touching the grid 
cage when the tube is warm.  [see photo on p. 15 in 9/90 QST]
Be sure to change the cutoff bias method from voltage to resistive AND 
put diodes across the meters or across the meter current shunt resistors. 
 
Rich---

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


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