Hi again.

Sorry for not replying earlier.

This series of Braun shavers had the option of a standard (slow) oscillating
speed, or for $$ or ££ you could buy the model with a faster oscillating
speed.

I have a 6510, which is very similar to the 6520 (one LED is missing).
It is one of the "Ultraspeed series" with "Oscillating head with
triple shaving system", i.e. two normal shavers next to each other
with a long-hair type one inbetween, which is supposed to take out
whatever the other two don't catch. It seems to work to a certain
extend. It still has a separate long-hair trimmer.

Anyone know the difference? I presume the motor is simply a dc motor and that
the faster speed is the result of a higher-rpm motor in that model.

In the service manual 5705 I got it says:

Drive: 2.4 V d.c. motor.

Number of revolutions with operating battery
after a minimum of 3 minutes charging time:

only cutter block min. 6900 rev./min.
max. 8500 rev./min.
with long hair trimmer min. 6600 rev./min.

I had the idea to somehow speed up my shaver, but I see that this might not
be practical.

Maybe you could check out

http://63.230.9.155/braun/Srv_Man/SHAVER/

and have a look at shvcross.pdf to see whether your model is listed as
well.

I hope this helps,

Christoph