Fixing up the Lego Steam Cargo Train (7722)
ⓘ These instructions may also apply to other Lego 4.5V trains such as the Diesel Freight Train (7720)
- Remove lid from battery box car and clean contacts, e.g. with vinegar to remove battery corrosion
- Using a small knife or screwdriver, spread the contacts of the cable that plugs into the motor so it makes better contact
- Out of the box the contacts are too small and loose on the side that connects to the motor
- If there's a squealing sound coming from the motor box, it can be disassembled and lubricated
- If the train motor wheel rubber rims are missing or deteriorated, they can be replaced
- If the wagon train wheels are dirty, don't try to remove them!
- They're connected with a pin but the pin will break if you try to remove the wheels. Clean as best as possible or you can replace them with a more modern set of wheels:
It takes 3 C batteries, which are overpriced and less common than they were when the train was released
- Use AA-to-C battery adapters in order to use AA batteries
- 👉 If you do this, you will need to add metal (e.g. aluminum) foil or some other conductor to the underside of the cover of the battery wagon opposite where the cable plugs in, in order to make a connnection from the top of the battery at that end to the metal contact of the underside of the cover (see image below)
- The train seems to run just as fast with AA batteries, just for not as long
- Use Japanese made rechargeable batteries
- e.g. Eneloop or Ikea
- Make sure the contacts in the battery box are cleaned
- Try new batteries
- Test the voltage of the battery box with a multimeter
- Test the connectivity of the cable with a multimeter
- Open the motor box and make sure the motor is working
- Try turning the motor box around; sometimes it works better in one direction
