There are two potentiometers that will have an effect on the forward power
indicating bar graph calibration. R1 and R4.
I recommend that you do not mess with R1 (without some more information)
because that setting will also have an effect on the forward power AGC
action.
You can twiddle R4 to your hearts content and it will not mess anything up.
It will only change the bar graph calibration. The voltage sent from that
potentiometer to the bar graph does nothing else.
The two AGC pots are part of the overdrive protection system. R3 AGC F
determines what power output the system thinks is too much. R7 AGC IC
determines what level of PA transistor collector current the system thinks
is too much. If either of these thresholds is exceeded relays KA and KB on
the INPUT BOARD switch in an attenuator on the RF input to the amplifier,
reducing the amount of drive that actually gets to the four way power
divider to drive the four sections of the amplifier. The attenuator is an L
configuration with a 5.9 Ohm resistor in series and a 200 Ohm shunt. I
haven't done the math to figure out how many dB attenuation that works out
to.
DE N6KB
On Sat, Jun 1, 2019 at 8:27 AM Gary Hendricks <k4mt1950@charter.net> wrote:
> I just acquired a Hercules II and the power meter lights the red bars at
> about 400 watts. I looked at the control
>
> board and saw an adj named bar. Is that the adjustment?
>
> Also saw two pots that say AGC. What are they for?
>
>
> Is there some specific procedure for adjusting bar graph?
>
> Amp does put out over 500 W and tests done into dummy load.
>
>
> Gary K4MT
>
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