[Amps] Best way to tune a Dentron ML2500 ?

[Joe Subich, W4TV]

R. Measures wrote: 
 
> Eimac specs the 8875's grid diss. at 5W max., typical grid-cathode 
> driving potential is c. 42v-pk, or c. 30V-rms.  I = P / E:  
> 5W / 30V = > 0.1666A, so two 8875s should be able to withstand 
> 333mA of grid-I without exceeding the grid-diss rating.

You've got to be kidding - 333ma is nearly the rated PLATE current! 

Eimac recommended a grid current trip at less than 100 ma for the 8877 
which has a significantly larger grid than the 8873/8874/8875.  I would 
never want to see more than about 25 mA of grid current per tube  in 
an amplifier using the 8873/8874/8875 tubes.  Unfortunately, Dentron's 
grid metering shunt in the MLA-2500 resulted in 1 A full scale on the 
grid meter.  It made it very difficult to see when the amplifier was 
being over driven.

Abuse killed more 8875s than phantom parasites ... 

73, 

   ... Joe, W4TV (ex K4IK)