After many years of service the relay RL2 that activates the PTT to a linear amplifier can become unserviceable and its replacement is an elaborate process involving the complete removal of the Control PCB.
All this can be avoided by substituting the relay with a transistor that can be mounted physically on the Remote Socket and only one resistor leg needs to be cut on the Control PCB:
For use with a TL922 amplifier it is necessary to use a high-voltage transistor such as the MJE340 and a zener diode of 150V as it has a 100V DC relay coil that must be grounded for TX operation. This modification will work on any amplifier requiring pull-down for TX. If the pull-down is only for 12V, the zener diode voltage can be lowered to 15V or eliminated all together if there is no relay.
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