[Amps] SB-220

[Joe Isabella]

Yep -- it's a good design, too.  It has a four-position rotary type main switch that is arranged so you can't get to the 3000/4000V position without first going through the position that has a *BIG* resistor in series with the input to the HV transformer.  It's actually a heating element that screws into a standard lightbulb socket.  It goes Off -->HV w/resistor --> CW 3kV --> SSB 4kV.  
 
An improvement that I'd like to add to mine is outboard manually operated Blower/Fils/Standby switches sequentually arranged so it can't be keyed unless all switches are on.  That's right, no standby switch on this one -- it's either on & inline, or totally off.  I also hate that I can't turn off my amp and let the blower run for a while...
 
Joe, N3JI

"R.Measures" <r at somis.org> wrote:
Dan -- I have never measured the fil V in an AL-811. The only RF-Tx 
amplifiers that do not benefit from a step-start are those that already 
have one. The Henry 3K-A is one example.


		
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