[Elecraft] Ameritron 240V inrush limiter: any benefit on a KPA500?

[Jim Brown]

On 1/18/2020 12:14 PM, Victor Rosenthal wrote:
> The power switch in some of those amps like the SB220 or TL922 is highly 
> stressed. T

My late '70s vintage Ten Tec Titan amps include circuity to minimize the 
turn-on transient, at least some of which is due to charging of the 
capacitors in the LV and HV power supplies. A surge to charge these caps 
is inherent in any capacitor-input PSU, and the strength of it depends 
on where in the 60 Hz cycle it amp is turned on. I own three of these 
amps, and the circuit values was a running production change that 
evolved over time.

This became a serious problem in large sound systems that included a lot 
of big power amps; with several amps on a circuit, it was not uncommon 
for breakers to pop when a system was powered up. In the largest 
systems, a turn-on at the peak of the cycle could take out the main 
breaker! Several schemes were developed; Crown, for example, developed a 
circuit to randomly delay the turn-on of their amps, and several 
companies developed dedicated sequencers that sat between the amps and 
their outlets.

73, Jim K9YC