[Amps] 3CX1200Z7 backup tube?

[Han Higasa]

Hi Gents

I have 6m HB amp using a 1200A7.
At first it worked as a bronco; 
burned RFC and LPF; it became a lamb
after adding a neutralization circuit. 

Filament voltage/current: 
1200A7: 7.5V / 21A
1200Z7: 6.3V / 25A 

Base: 
both fit for SK-410 but Z7 has dedicated grid ring.
A7 will work better with a neutralization.
Z7 stable with no neutralization.

I have heard 3-500Zs will get worse while 
strage while 1200s not.

de Han JE1BMJ