Beogram 4002 (5513): DC Platter Motor Not Spinning Anymore

I restored the PCBs, DC platter motor and RPM panel of a Beogram 4002 from a customer in California in January 2021. Recently he contacted me stating that the platter motor stopped spinning. I asked him to return the parts so I could have a look.

After I received them I implanted them in my bench 4002. Indeed the platter motor did not spin anymore! The culprit was found quickly after checking the motor voltage at the red wire of the motor harness. I only measured 2.4V. It should be around 9V if everything is o.k.

The motor voltage is stabilized by 1TR2, originally a TIP31 power transistor. Since the Zener diode still made ~10V, it was most likely the transistor. I replaced it with a stronger TIP41:

And everything was good again in the motor voltage department. 9.6V at the red lead!:

In 2021 I had not understood yet that the power transistors on these boards often have issues. Maybe age related, maybe just wear from years of playing records. Informed by repeat transistor failures that I encountered over the years, I now always replace them all when I restore a Beogram 400x. So I set out to update this board to my current state-of-the-art. It is best to replace the two power transistors mounted on the solder side of the board when the board is installed. It makes it easier to position them correctly that the mounting holes match up. This shows 1IC1, which regulates the 21V power rail. It is usually a TIP120:

I always try replacing power transistors with stronger types for enhanced longevity. In this case a TIP102 is a good choice:

For some reason modern TIP replacements need some capacitance at their emitter in this circuit configuration to prevent high frequency oscillations superimposed to their emitter output. That is why I soldered a 100nF cap (yellow-orange) between the emitter and a conveniently located GND solder point nearby in the above picture.

The second transistor on the solder side, 1IC4, is usually a TIP125, 

whose stronger cousin, the TIP107, makes a good replacement:

After this I removed the board and also replaced the often fail prone H-bridge transistors with new types. this shows the updated board with the extracted parts:

I installed the board again and successfully tested all functions. These parts are ready for duty again and will soon travel back home to their Beogram 4002 in California!