The (mini-) modification consists of adding a switch to toggle between self-oscillation on/off modes.
To do this i had to use an extra 4 HP wide blank panel because there isn't enough space left on the A-124's front-panel to add a switch.
This is not my first 'expansion module',
i made one earlier for my A-127 Triple Resonance Filter
I did this modification in less than an hour; i carefully drilled a 6 mm. hole in a new 4HP blank panel, desoldered one side of the resistor that i added earlier and connected that one to the new switch.
Another piece of wire connects the other side of the switch back to the original position of where the resistor was connected.
I am very happy with the result, i can now manually switch, turn the resonance-knob up to self-oscillation and simply switch back to the original mode again...
Thanks to Tony Steventon from Synovatron for the project review