[Amps] 4CX1500B QSK

[Mark Hill]

Folks,

I'm looking to QSK an ex-commercial amplifier which uses a 4CX1500B.  The 
amplifier has no changeover mechanism at all at present (it was part of a 
TX system that was on 24/7 with remote receivers).

I intend to engineer the aerial c/o using a vacuum relay - the rest I would 
like to do in solid state.  Any experience on the line regarding the 
relative merits and de-merits of different methods of taking the valve 
between 'correctly biased ready to go' and 'cut off with no noise in the 
RX' states?  To cut the valve off, my options would seem to be:

 >Shift the grid bias from operating (normally about -35V from a pot across 
a Zener) to some greater negative potential; or
 >Remove screen voltage (normally about 225V from a string of Zeners) and 
ground the screen terminal of the valve; or
 >Both!

Having been a 'triode in GG' station for over 20 years, I thought I would 
try an extra grid and see if it's worth a candle!  All input appreciated.

Regards.

Mark.