After a few years of use, I realized that the standlight in my B&M Toplight Line Plus dynamo rear light quit working. I normally rely on my own backup system but, due to the change in configuration, I had to fall back onto the backup in the light. I was dismayed reading many online reports, mostly in German, on the standlight in that lamp quitting to work and, encouraged by this earlier thread, decided to open the lamp and to investigate.

The lamp is sealed, but its opening turned out to be relatively easy. I slipped a rounded knife between the plastic parts of the housing and moved it along the circumference with the glue relieving the two parts without any breakage. The interior looked grim. One of the standlight capacitor tabs was detached from the capacitor and from the PCB board. Prior to breaking off the board, that tab seems to have corroded through. One connection between the two sides of the PCB was also corroded through and not connecting. Signs of corrosion were evident in different places. The basic issue was that, while a soldermask was applied, there was no coating of any sort applied thereafter - all solder joints and component terminals were left exposed.

After I fixed everything, I could see that the circuitry operated fine when immersed under water. Still coating is needed to ensure durability. I thought that the sealed housing was there to protect the interior, but apparently water has no problem getting in. In addition the capacitor tabs seem to be too feeble to hold the capacitor in long term under typical bike conditions. I expected better from B&M. I will be applying coating before putting the lamp together.