to lower the deadkey on the 520xl (the schematic i looked at is for the 520e, but the part numbers should be the same), you do not want to lower the power by de-tuning L5 and L6.
this will cause an impedance mismatch between transmitter stages, and wont be good for modulation.
first, tune L9, L6, L5, and L4 for maximum swing while saying "ahhh" into the mic.
do not tune them for max deadkey. you must tune them for max watts while speaking into the mic.
once you get them peaked, then lower the deadkey of the radio down to about 1 to 1.5 watts.
the way to lower the deadkey is to locate the anti-spiking diode (D7), which is a 1N4003 rectifier diode right near the modulation transformer.
this diode sends voltage to the driver and final, and by adding more 1N4003 diodes in series with it, you will lower the voltage to the driver and final and thereby lower the deadkey.
modulation will not be reduced by doing it this way.
so get yourself some 1N4003 rectifier diodes, and a wattmeter.
by experimentation, you will find out how many diodes it takes in series to lower the deadkey down from 4 watts to about 1 to 1.5 watts.
if you want to remove the modulation limiter, its D14, but you may find the radio sounds bad after removing it, so get some radio checks, and if they all come back as distorted; put the diode back in.
you can turn VR4 up for more receive gain, but at some point it will create too much noise, so dont just turn it up all the way.
best to do it bit by bit and stop where you are happy with it.
good luck,
LC
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