2. cont'd...
I measured the N-MOSFET power transistors (
IRFB3607 P512D in
TO220 heatsink packaging- there are 12x, 4x per phase), 2x of them which belongs to 2nd phase was broken.
(Here is the data sheet:
https://www.infineon.com/cms/en/product/power/mosfet/12v-300v-n-channel-power-mosfet/irfb3607/)
If you connect a multi-meter in "Diode" measurement mode, you can see if the transistors still good or they were dead. In my case, 2x of them were showing "short" i.o. showing 0.5V forward-bias on voltage drop.
Assuming the remaining 10x working power transistors may also be worn out, coming to their end of service life, I decided to replace all 12x at the same time. Each costing about 2.5 CHF in (
www.digikey.ch). Note that, opening/closing such a hub-motor is pain in the neck, it is better do a "preventive" maintanence/replacement before the other also die later ;-)