The most popular mod. is to raise the screen voltage to 325 volts.
This is easily done by adding a small 100 watt isolation transformer
115v/115v in series with the winding on the screen supply transformer.
You then adjust the grid voltage and reset the r.f. sampling voltage
to the tuning meter.(The new transformer sits on the shelf above the
main power transformer)
This mod doubles the power output of the amp while maintaining that
good, clean Collins signal.
Collins used 200 volts on the screen to limit the power input to the
1 kw limit to comply with the rules in the old days. This resulted in
an efficiency of around 25-30%. The above change has resulted in
efficiencies of 58-66% in typical 30S1's.
(((73)))
Phil, K5PC
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