Hi,
it happens that very recently I was wondering just your same questions, regarding universal type motors and how to reverse its direction of rotation.
Its seems to be be very possible and easier than expected.
I came across the need for a little universal type motor, of about the same overall size and format of the Geteg Ug-7750, that originally came with my U3.
Locally I might get an original Rowic HM-175 motor replacement, that has 120 Watts and reaches 12.000 rpm, that needs no modification in that regard, but costs $190. That is a high price, even with a factory direct discount.
Besides, it has a very high speed without load, that I assume is the same for most DB-200/SL-200, but not suitable for a U3, which is designed for a max. 5000 rpm. I guess they have a much greater pulley reduction.
On the other hand there are sewing machines motors, most of them of about 100 Watts, and 7000 / 8000 rpm. These costs 1/4 of the Rowic price, but have a standar CCW direction of rotation.
However, in this case there is the need for altering the direction of rotation, but also the motor shaft are 8mm in diameter and much shorter than the 10mm x +30mm long of the Ug-7750.
So I found the following Youtube video, that explains how to do the job in most electric motors, but in particular the universal type ones, begining at minute 9:04.
I also found this article that covers the same topic with much the same conclutions:
I hope this helps in some way. Regards
