On Sun, 2007-09-23 at 22:36 -0500, Bob McGraw - K4TAX wrote:
> The control of PA current is derived from a R in the A+ line to the PA. The
> voltage across the R is fed to the 2nd mixer board and driver which reduces
> drive inverse to the PA current. The current never gets to max
> destruction value.
>
> Having a Paragon manual in front of me, the current sensing R is R1 {0.015
> ohm 10W} located on the DC power board. This voltage is fed to U2a which is
> a level shifter and its output feeds U2b to which the output if it exceeds
> the Ic limit of 22 amps at full power, diode D25 is forward biased and ALC
> actions results, therefore reducing drive to the PA stage. Thus PA current
> will always be limited to a max of 22 amps for some 300 watts input
> regardless of load Z. Yes, in theory, it will drive a dead short with rated
> output. Remember the Tentec PA is not current limited. It is drive
> limited.
>
> The fuse, the circuit breaker and power supply limiting serve no purpose
> except
> in the event of catastrophic failure and thus exists simply for the
> protection of
> other components.
>
> Big difference.
>
> 73
> Bob, K4TAX
I can't find my Corsair II manual at the moment, but I've not observed
that collector current reduction in my Corsair II. Given a bad load Z it
simple blows my fuse protector.
73, Jerry, K0CQ
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