Update: After consulting with TCS, I no longer recommend the TCS Z2 decoder for this installation. Sadly, the TCS M1 is too large for this installation, and so I have selected a Lenz Silver Mini to replace the Z2.
Previously, I showed how to disassemble the tamper down to the point where we can proceed with decoder installation. Let’s move forward with the decoder installation itself.
Decoder Installation
Isolate the green areas; cut traces and solder where indicated
First, isolate the motor. This is where my instructions diverge radically from the official instruction sheet. Please examine the diagram to the left carefully. First, the motor contacts on the circuit board can make contact with the unpainted frame interior around the engine. Use a clear acrylic nail polish—preferably a “top coat” (ask your wife), which is quite durable—to paint the inside of the frame where motor contacts press against it. Second, the wipers on the truck can contact the same motor contacts in a sharp curve. So apply Kapton tape to the rearward part of the circuit board, and a sharp hobby knife to trace the outline of the motor contacts and associate circuitry, to prevent the wipers from making contact when the truck is turned to the extreme left or right.
I find a sharp needle file is actually better than a saw for cutting traces, despite the photo.
Next, again following the above diagram, or the one included with your tamper, file or saw the circuit board contacts in two at the points indicated. Be sure to check your work with a continuity tester or multimeter.
With the motor isolated, reinstall the motor and truck top.
Isolation complete, re-mount the motor and truck bottom. Slide the truck into the circuit board, being very careful of the wipers. They will try and get caught on the circuit board, and its very important that you don’t let them, else you will have a nasty mess on your hands trying to reattach the wiper to the truck. It is important to do this now, because once we’ve soldered wires to the circuit board, the truck will not go back on. Also, don’t re-attach the truck bottom yet, as it will just get in the way of soldering. Finally, this would be a good time to make sure the wipers are making good contact with the circuit board. If not, pull the truck back out, and bend the wipers to improve contact. After the next few steps, you won’t be able to come back and do this again, so take the opportunity while you have it.
Trim the shrinkwrap from the red shaded area, on one side only.
Unlike the Z2, the Lenz Silver Mini does not come wrapped in heatshrink material, so please ignore this step. Looking at the diagram just here, trim away the Z2′s shrinkwrap from the shaded area. The space in the cab is just big enough for the decoder; there isn’t enough room for the wires coming out the end. By trimming back the shrinkwrap, we can let the wires come out of the sides, freeing up considerable room. You only need to trim the shrinkwrap back on the top; leave the bottom as is.
You'll need to coil the function leads much tighter than I have here.
Place decoder with orange and red through one hole, grey and black through the other. Use some double-stick tape to hold the decoder in place inside the cab. Either trim off the function leads, or coil them up tightly and tape them on top of the decoder (as I’ve done here).
All four leads trimmed and soldered. Use a small pair of tweezers to bend the leads to your will, and to hold them in place while soldering.
Trim the leads down a good bit, then strip and tin them. Following the diagram at the top of this post, solder leads to traces. Grey and orange (leads that attach to the motor) go to the outer-most traces, red and black (leads that go to the wheels) to the inner-most. Check with a multimeter to make sure that you haven’t shorted the motor to the rails by soldering the leads too closely together!
We’re done! Reassemble the truck. Use a little PVA glue sparingly to hold truck together. Insert the frame back into the shell. Re-install the motor retaining plate, watching the brass wire and the black wire closely to ensure they go back as they were. Throw the puppy on your test track and see if you can read the address.
Presuming testing on the programming track was successful, reinstall the details, again using PVA glue to hold the detail pieces in place.
Enjoy! Or try to. You’ll probably find at this stage that the performance is a bit dodgy, with a lot of stalling. Read on to see what can be done.
Tips for Better Running
If your tamper is stalling intermittently or constantly, the problem is with the various techniques that are used to conduct the signal from the rail to the decoder. Problems can occur in the wipers, which transfer the signal from the wheels to the internal wiring, or in the contacts between the rear circuit board and the internal wiring.
Take apart both trucks, and carefully bend the wipers to make better contact with the wheels. Unscrew the rear circuit board (the one you didn’t solder to) so you can remove that truck, and bend the wipers on the truck to make better contact with the circuit board. In the model I had, the circuit board was covered in grime and corrosion (!!); cleaning that off helped tremendously. A little Conducta (conductive lubricant) at the points of contact will help a bit too.
Side view of circuit board in situ. Tighten the brass contact tabs on the circuit board so that they squeeze the brass wires tightly against the circuit board.
Finally, if you are still having issues with stalling, do this. Test the continuity between one of the rear wheels, or the rear circuit board, and the brass wires that run up the middle of the model; if you find the circuit open, then the rear circuit board is not making good contact with those brass wires. We will need to reshape the contacts. Remove the rear circuit board, and observe the brass contacts. They point upwards and outwards. We need them to point less upwards, so as to firmly grasp the brass wires between the contacts and the circuit board, per the diagram just there. Use a pair of tweezers to flatten the contacts into more of an “L” shape. Then, reinsert the circuit board (with the truck mounted) into the frame, being careful to ensure that the brass wires sit; you want the fit to be quite tight, and so it may require some careful work and wiggling to get the circuit board placed correctly. Make sure that the contacts aren’t simply pushing the brass wire against the frame (which is how the original design worked), but are grasping the wires against the circuit board.
And there it is. Your tamper should be running considerably better now. After performing these steps, the one I’m working on actually runs pretty well.
Final Notes
I haven’t given instructions for installing lights into the model, because the model has almost no provisions for fitting lights. Installing lights will require the fabrication of custom light pipes from fibre optic, something I have no experience with. I had originally thought that at least getting the beacon on top of the cab would be easy, but in fact, there are four layers of plastic separating the decoder from the beacon, two of which are for the cab windows, and hence likely to pose a problem (in that I don’t want the beacon light to leak out along the clear plastic of the windows). Perhaps this is something to revisit at a later time, but I suspect most readers will, as I have, quickly lose interest in attempting to install lights.