I think you will find it is the PTT you are not supposed to use with an amplifier. This is a low level, low current switch and meant for foot pedals as an input. The Standby socket however can switch relays up to 24vdc at 100ma but a typically the switching relay voltage is 12vdc 25ma ~ 75ma. The circuit is open collector transistor.
Regarding the PTT:
Note: This jack is designed to be used for external
PTT input only. Do not attempt to use the PTT jack for switching amplifiers or other external devices (use the STBY jack for controlling such devices .
Without the ALC (which will accommodate up to -4vdc) you will guarantee to put any connected amplifier at risk of runaway.
Personally I run my FT847 into my VL1000 at full output (100w) and then adjust the ALC to 1000w. No matter how much input I put into my VL1000 it won¡¯t be overdriven. The limit in the UK is currently 400w so can be safely driven at much lower drives to achieve that and just in case of band switching and then running 100w into a relatively low ALC and overdriving my amplifier and damaging it. With this simple precaution it¡¯s impossible to run more than 1000w.
De Spence M0STO
Sent while portable! please excuse typos.
Spence G5STO