[Amps] AL-1200 Grid Current - negative?

R.Measures r at somis.org
Sun Nov 9 07:56:01 EST 2003

***  To find out, remove the tube and fire it up.  If the grid current is 
zero, the chances of the 3cx1200A7 having a filament to grid short are 
pretty good.   However, this is a rare occurence compared to 3-500Zs.  
Rather than replacing a 3cx1200A7, I would look at modifying the amp to 
take a 3cx1200Z7, a tube which has 0.075pF of feedback C - as opposed to 
0.2pF of feedback C for the 3cx1200A7.   The price of a Z7 is c. $20 more 
than an A7.  

>What does it mean when you power up an AL-1200 and the grid current meter 
>pins negative (no drive power supplied)?
>   Dana
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