The owner of this Perfect Prep machine had reported that it had not been used for a while, then filled with water, powered up and … nothing.
Make and model: Tommee Tippee Perfect Prep
Cost of replacement: £70
Cost of repair: £3.69 (plus my time)
Hours spent on repair: 1 (plus testing)
Repair ease: 4/10
I’ve repaired a machine like this before and I already had a theory about the problem, which went like this:
- Machine not used for a while; watery scale deposits built-up in machine
- Machine filled with water, with possible air-lock present
- Air-lock causes bubble in heater, causing it to temporarily over-heat, safety thermal fuses blow
At this stage, it was only a theory, so the only thing to do was to start wielding screwdrivers.
A few quick checks revealed that mains power was not getting to the main controller in the machine, which indicated that the safety thermal cut-out fuses had failed. There are two on this machine. A quick test with the multi-meter confirmed that both had failed.
After some dismantling, both fuses could be removed from the wiring harness. Fuses like these are not available from the high street usually, but they are readily available online. The manufacturer had used crimps to attach the fuses to the wiring, but I decided to solder the new ones back in place. Care had to be taken as the melting point of solder is very close to the thermal rating of the fuses, so I came up with the idea of using a damp cloth wrapped around the fuse while doing the soldering. A bit tricky!
Both fuses replaced meant that the unit powered-up and worked. Great.
However, I wasn’t totally convinced that an air-lock wouldn’t happen again so I looked deeper at the machine’s plumbing. There appeared to be a kink in one of the boiler tube feed pipes, so I decided to cut some material away, to prevent the pipe restricting water flow in future.
All back together, the machine worked well once again.