Have you tried the Bosch web site
and/or talking directly to them. They have always been very helpful
when I've dealt with them.
I just looked at my Bosch drill and it's a CSB 520 2E with the
electronic trigger speed control. I bought it about 1985 to replace a
B&D that decided to commit suicide by loosening a screw and taking out
the fan blades. The only thing that's failed on the Bosch has been the
strain relief on the mains lead, everything else including the trigger
speed controller has been fine. The most abuse it has seen IIRC was
drilling deep holes in concrete fence post footings to help break them
up, that got it smelling a bit hot. It's still going. I'm quite
impressed with Bosch products, I've not had one fail yet. My big angle
grinder is a Metabo 5", the other is a blue Bosch 4.5" which is much
lighter and nicer for single handed use. All the other Bosch stuff is
green DIY stuff and seems to stand up well to my use.
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