The trick was to disconnect the battery from the chip for a couple of minutes to force a reset. Here’s how to do it:
- At the lanyard fixture, you will find two wee small screws which hold the two shells of the device together. Remove them.
- Use your finger nails or any other non-scratching tools to gently spread the shells. Inside there are three plastic hooks on the opposite side of the screws. While opening the device, I broke one of them. Obviously they are made for assembly only, not for disassembly.
- The board is fixed by three screws. Remove them. Make sure to keep them separated from the other two, as they sligtly differ.
- Take the board out of the shell.
- On the left hand side, you can see the antenna. On the right hand side, the battery. Between both, there are a couple of cables fixed to the battery. The goal is to disconnect the red one. Use a sharp knife to remove the adhesive tape from the red cable pin.
- Use a soldering iron and a pair of tweezers to disconnect the red power cable from the battery. Wait a couple of minutes (e.g. 5′) to reset the chip’s memory.
- Resolder the cable.
- Switch the device on and put it on a window board. Check whether it is operational.
- If so, reassemble the device.
Here you can see the pin in question:
Here you can see the clip I broke:
Tomorrow I will check whether it is fully operational. If so, I will have a good chance to compare the tracks of the Blumax with the track as recorded by the WBT-201.
Credits go to Christian Thäter who sent me the essential hint. I owe you a beer :) .