Thursday, July 17, 2008

How I chipped my Zillertalbahn U-class 0-6-2T locomotive

You will see from Progress Report 9 that I bought a refurbished LGB Zillertalbahn U-class 0-6-2 loco from Bay Models which, one day, I will anglicise. For now, I'm quite happy to have it chugging its way around the layout in unmodified form and I must admit it is beautifully modelled. However, as it is a rather early model it was not digital-equipped and so needed some thought as to how a chip could be added.

As it was not a simple case of plugging in an LGB chip, I opted for a Massoth 3 amp chip. Not that it draws 3 amps but the Massoth chip offers a few more options and is slightly cheaper!

Here she is in all her splendour! First job was to remove the cab. On this version, two small cross-head screws just above the buffer beam on the rear of the cab held it in place.

Two lugs at the front of the cab needed to be eased out (more of these later) and the cab was lifted off. As can be seen, the contact block resting on the coupler also dropped out at the same time.

Next, the chimney needed to be removed. There was no smoke unit on my model, I assume the lead would have to be unplugged at this point if one was available.

The chimney was simply unscrewed from its retaining nut and then
eased out. One of the simpler jobs!

Next, the coupler needed to be pulled out. This could only be done once the chimney had been removed.

Finally, two screws at the font of the cab needed to be unscrewed......

..... and at last the body could be lifted off from the chassis.

The next job was to remove the cover from to expose the motor. The six screws holding it in place were quite prominent.....

The motor was simply slotted in and so was easily removed once the cover was lifted off.

I decided that the next job was to attach wires to everything which needed to be connected to circuit board. First came the all-important motor. The contacts on the motor press against the brass strips which transfer the power from the wheels. The instruction booklet makes it very clear that not only should the digital circuit board be wired between the power source (ie the wheels) and the motor, no contact should be made directly between the track and the motor, otherwise the delicate chip would be blown.

To ensure the motor contacts could no longer make contact with the brass strips I cut them in half and bent the brass strips as far back as they would go. I then soldered two leads to the motor contacts to allow them to be connected to the circuit board.

I then disconnected the wiring for the two rear and front lights and the interior lights. Firstly the contact strip was removed.....

The front-most weight was removed ..........

........ to reveal the diode which controls the directional lighting.

This was cut off as the circuit-board provides directional lighting.

In the same way as the motor needed to be isolated from the track, I took the precaution of cutting the brass contact strips to ensure the lighting in the cab and the rear lights would be operated only through the decoder.

Wires were soldered on to these contacts. The two contacts on the left provide the power from the track. The lower contact on the right is the common (+) connection for the rear lights and the cab light. The upper contact on the right is for the rear lights whilst the middle contact is for the cab (interior) light.

The motor was fitted back into its housing and all the leads were connected to the relevant sockets on the circuit board, using the diagram in the handbook.

Now came the interesting (and somewhat frustrating) bit. Deciding where to put the circuit board. The Massoth board is slightly larger than the LGB version as it has a terminal block at each end which makes attaching the leads straightforward - but takes up more space!

I decided that, by cutting the rear lead weight in half and turning the two pieces through 90 degrees, I could fit the board in between them.

To hold the circuit board in place, two strips of plasticard were cut and placed across the board. These would be held in place by the weights.

I drilled a hole in each weight to line up with the original fixings. A mistake I made with the lower weight in the picture was that I left no space between the weight and the front of the cab (to the left). The space is needed to allow the lugs at the front of the cab to slot in, as can be seen with the upper weight in the picture.

The model was then reassembled, making sure that none of the wires was trapped in the process and the loco was programmed and tested.

Inevitably, I found I had wired the lights and motor incorrectly so that the rear lights came on when it travelled forwards and vice versa. The loco was disassembled and the leads to the motor were swapped over. This time I loosely assembled the loco to check the lights were synchronised with the direction of travel before fully reassembling.

Touch wood - everything seems to be working as it should. Maybe I will add a sound chip next..............

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