Indeed, there is no drop adjustment speed.
The tonearm drop works according to the principle that there is a zero balance condition that means the net force of the arm, headshell and cartridge is countered by an equal opposite force consisting of the counterweight AND an up force created by the electronics (fixed magnet with magnetic field near a variable coil current principle). When the unit is auto balancing the arm on start-up and on return to the rest position, this zero balance condition is calibrated. Apart from that there is another circuit that applies an electrical force that is set by the user with the tracking force dial. Both these adjustments need to be calibrated to work properly.
If the arm drops too fast (or far too slow or does not drop at all) this means that the zero balance and/or tracking force adjustment is off. If they are spot on, your tone arm will drop nice and slow and steady. On most of these units, being 35 years old and unserviced, these adjustments are off.
These are essential adjustments that make sure the correct stylus pressure is applied. Next to that there are about 20 of other adjustments that need to be made to ensure the correct and optimal performance of the Biotracer arm (motor speed, vertical motion feedback, horizontal motion feedback, arm angle sensitivity and offset, to name some).
It can be done but you need knowledge, patience and time to perform these adjustments properly. It is also quite probable that you'd also need to replace several capacitors and probably some of the cheap adjustment pots that Sony used to reach a proper calibration.
Another thing that happens quite regularly to these units is a bad contact in the large bunch of extremely thin wires and/or solder connections on those wires that go from the PCB to the tone arm, resulting in erratic behavior of the arm as it travels over the album, since those wires get into different positions during this travel. In this case, all the coils and wires need to be checked for proper operation by measuring their respective resistance/continuity.
