Lego Duplo 2961

This Duplo locomotive (part number 2961) isn’t working properly anymore. The bush button under the left yellow hood is broken. In this post, you’ll see how to open this locomotive (which is probably the most tricky part) and how to replace the damaged switch.

Tools you’ll need:

  • slotted screw bit with the dimensions 1.2 x 8.0 mm
  • gas pipe pliers
  • letter opener or another slim and strong tool
  • soldering iron
  • solder
  • replacement push button 6 x 6 x 4 mm (width x depth x height)
  • glue (to bond the push button on the circuit board)

Tools

For opening, you’ll need the right tools and probably some force – not too much, but right enough. I recommend gas pipe pliers and a slotted screw bit . The bit should fit as good as possible so it won’t damage or cut the locomotive’s plastic. I took  a slotted screw bit with the dimensions 1.2 x 8.0 mm, which worked perfectly.

Open locomotive 1

On the underside of the loco you’ll see two gaps filled with plastic from the body (in my case blue, check the highlighted box). Put the screw bit exactly on a gap and use the gas pipe pliers to press the latch from the body out of the chassis (in my case the yellow part). Make sure, to place on bracket of the pliers on the bit and the other one on the small rim of the body. Use well dosed force. Proceed the same way with the second latch.

Open loco 2

At the other end of the loco there is one big latch – apply the same procedure here as well. Be careful: The body and the chassis are still hold together by some latches on both sides of the chassis.

Open Loco 3

Use a slim but strong tool to lift the plastic from the chassis (yellow) from the notches of the body (blue). In my case my letter opener was the perfect tool :-). Try to shift the body out of the chassis a little bit, so the notches won’t snap back in again. Do the same steps on the other side of the locomotive.

Locomotive is open

Here we go! This is how the toy looks inside. Highlighted with the green box you see the location of the defect switch. By proceeding, take care to remember which part belongs where. Taking som pix with a cam can be a good mnemonic trick.

Battery clips

The battery clips are easy: just lift them out of their sockets. Proceed the same with the wheels and the “gear box” (the two axles with gears over the motor). After that, lift the circuit board carefully out of the chassis. You might use some force, but take care to avoid breaking the board. On the side towards the motor the board is attached with double-sided duct tape to the chassis.

Switch

So, finally we got the switch. It’s a simple (circuit board-)push button. Its dimensions are 6 x 6 x 4 mm (width x depth x height). You can buy a replacement at your local electronic parts dealer or an appropriate web shop. Try to buy a model which has a preferably strong spring, so the plastic hood of the locomotive (which is the “real” push button) doesn’t permanently press the button.

Use the soldering iron to remove the damaged button.

My new button didn’t fit in the drill-holes in the board, so I took some epoxy glue to stick it onto the board. I used to small wires to connect the pins of the button with the circuit path on the board.

After that, you can re-assemble the parts. This might be a good moment to clean the locomotive a little bit inside and apply some silicone grease on the gears and the axles (the points where they are mounted in the chassis).

That’s it! You just saved a solid toy from going bye-bye 😉

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