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VTX Expansion connector

Configuring and connections

The expansion connector is an optional extra, normally factory fitted when purchasing a controller. This page details the retro-fit.

To get the controller factory-fitted with the expansion connector you can order is from the VTX controller page.

The expansion connector can be used for two main purposes:

1. Double-heading miniature locomotives and geneerally using two contollers as a matched pair.
2. Adding a tachogenerator feedback loop

The expansion connection fitting is different for these two purposes. This page explains the changes.

Both fittings require some soldering to the board (removing a surface-mount component and fitting through-board connections) so fitting should only be done by the technically proficient. It is however not difficult!

4QD will not however be responsible for the results if mistakes are made in fitting the connector!

Warning: in early 2009, some boards was supplied to us with plated through holes. This means that all the links are already made. These boards are identified by bright metal plating inside the holes in the board.

Recent boards are all plated-through.

These plated-through boards already have all the links etc correctly set for double heading. All you need to do is to fit the connector and check that LK2 is removed.

For tacho feedback fitting is more complicated with plated through boards.

Fitting the connector and modifying

The 6 way Expansion connector fits as the diagram, right. This also identifies the points A, B, C and D - these must be linked through (as detailed below) from top to bottom of board by threading though the board a piece of tinned copper wire. This must be soldered on both sides. The bottom points of these connections are further identified (on the second diagram) by red dots. A is linked as standard and should not be altered.

Double heading

1. Fit 6 way connector
2. fit 3 though links, B, C and D.
3. Remove LK2 if fitted - see diagram below. (This removes +9v from pin 1, which becomes the ignition common)

Tachogenerator feedback

1. Fit 6 way connector
2. Remove LK3 - this disconnects the ramp output from the modulator input.
3. Fit LK2 (if absent).
4. If the board is plated through, cut the track topside from point C to point D. Easoes to cut near point D.

Notes on Tachogenerator modification

• When the tacho modification is fitted, the controller will not work without the tacho board in place. If operation without the tacho board is required, pins B and C must be joined.
• If the tacho generator is disconnected, then at a pot speed setting slightly above zero, the controller will accelerate to full speed. If the pot is again zeroed, the motor will be decelerated to zero.
• If the tacho feedback board is unplugged and B not connected to C, then the pot will have no effect and the controller will drift to full speed.

More information

For further information, see the instructions for fitting the expansion connector to the Pro-120 and NCC controllers.

The connector set can be supplied for customer retro-fitting: