The standard VTC/NCC controllers are designed to work with a permanent magnet motors. There is a factory option to supply them converted to suit series wound motors. This page shows the mofification of an earlier NCC but the modifiction to the VTX is identical, copper layout changes are minor.
This page describes the conversion. However - do not undertake modifications unless you have the required tools and the necessary skills. 4QD will accept no responsibility for your mistakes and it is likely that, if you have attempted conversion yourself, we will not repair the controller should this ever be required.
The way reversing works is described in our FAQ sheet. This page describes where the track cuts must be made, as mentioned there.
When using a series wound motor, you will get no dynamic braking so the deceleration ramp should be set long, so the controller will not reverse quickly. You should also set the reversing to 'Preselect' by disengaging dual-ramp reversing - see instruction manual.
The drawing above shows the centre section of the NCC-60/NCC-70 circuit board. Marked in green is the cut that must be made. You can use a sharp pointed knife to cut a break in the copper, or a small grinder to grind away the copper. Take care not to slip!
The field is then connected between points as shown by the thick red lines, marked on the drawing.
The modification for the NCC-35 is identical.
The NCC reverses a permanent magnet motor at zero speed. Because the controller is braking such a motor, the controller can safely assume that, when the deceleration ramp reaches zero speed, then the motor speed also is at (or very near to) zero.
However, with a series wound motor you cannot get regenerative braking. The controller therefore has no control over the motor's speed during deceleration, so (as it does not measure the motor speed) it cannot safely make any assumption about the speed of the motor.
It is therefore not necessarily safe to automatically reverse as the controller reaches zero speed. For this reason, it is probably best to disable the dual ramp as described in the instruction manual so the reversing is pre-select and occurs only when the demand speed (from the speed pot) is at zero.