Improving the Roco
BB 63888 (2)

Original page created on 25/07/2011.

New PCBs

The original PCBs take up a lot of space for few components. As I want to place the decoder under the bonnet and not into the cab, plus LEDs for red lights, I decided to make new circuits. They were not made without trial and error, and, when I think about it, I was wrong keeping the original lamps. Here is the very simple electrical diagram, taking advantage of the additional output of the Lenz Silver+ decoder (brown wire) for cab lighting.

Electrical diagram

However, you will see that the use of the older Silver decoder is planned on the PCB, which explains an apparent inconsistency in the wire layout, which has changed between this model and its successor.

Circuits (masks)

Here are the bare PCBs, seen components and copper side, since components are for surface mounting (SMD), except for those recovered from the original circuits (interference suppression inductors and capacitor). Board thickness: 0.8 mm.

The hatched area will receive the decoder end, where are the connecting wires. It will be stuck there with thin (otherwise, it would touch the bonnet) double-sided adhesive. The jutting out part will overhang the front flywheel — one has to check whether it does not touch it. The small notches visible on the front circuit make it possible to fit it on the chassis pins. But it is prudent to reinforce the holding of the circuit by gluing it, because it is no longer possible to use the original screws. On the other hand, the rear circuit will be attached like the old one, by two screws passing through two ⌀ 2 mm holes which must be drilled in the centre of the target-shaped pads. In addition, a rectangular hole must be milled to leave room for the anti-parasite inductors (caution when you disconnect them from their original circuit: I broke a wire close to the body).

Setting up

For connecting the two circuits, I used standard colour wires recovered on the decoder itself, because the decoder / front circuit link wires are very short. The wires which connect the two circuits pass on either side of the motor, in sheaths glued along the latter.

Some notes about these circuits:

• In the drawing, the space between the two circuits is not to scale.
• There are resistors (R3, R4) of zero ohm; they can be replaced with a simple piece of copper wire. They are intended to be replaced with real resistors in case the incandescent lamps were replaced by LEDs.
• As stated above, the decoder must be stuck close to the pads where the dotted lines end. The wires to be soldered on these pads are very short and this may be sporty!
• The strips feeding the cab LED come into contact with the PCB on the rectangular pads marked Ecl. cabine + and Ecl. cabine –.
• The lamps and LEDs arrangement is described in the following paragraph.