Troubleshooting High-Speed Rotation in Unitra GS 434 'Bernard' Turntable

Hello all! Recently I decided to fix "Bernard" that belonged to a friend. The first problem was the engine, it did not spin at all after pressing the START button. It was enough to replace the fuse located on the board. After switching on, another problem appeared. The engine was spinning too fast. With the setting of 33 revolutions, the upper scale on the plate, responsible for setting 45, "worked", and after changing to 45, it spun even faster. The circuit breaker also does not work, but when I wanted to measure its resistance, with the engine on, after touching the "probes" of the meter, the engine turned off (I shoot that the F1 photoresistor is simply to be replaced). Then I measured the voltage of the bulb responsible for regulating the engine speed (with the engine off it is 17V, with START33 it is 16.3V, and with START45 the voltage is 16V). The voltage on the motor at slower revolutions is 2.2V, and at faster revolutions it is 4V. The voltage on the C9 capacitor at STOP is 16.8V, at START33 it is 16.1V, and at START45 it is 15.9V. The voltage on the secondary winding at STOP is 17.3V, at START33 it is 17.2V and at START45 it is 17.1V. So, a question for you forum members. What could be causing these too fast spins?

Thank you for your answer do I have to replace them all, or is it enough for me to measure their capacity and only list those that "qualify"?

Bogdan K wrote:

First, I would replace electrolytic capacitors with new ones, additionally I would put in new PR (p1, p2, p3, p4).

And I would check or replace the F2 photoresistor and the bulb that works with it.

Problem almost solved. In place of the 10k ohms variable resistors responsible for the speed of rotation, I put 22k ohms, adjusted and it's ok, only now after connecting to Radmor, I noticed that the left channel has a slight distortion and Bernard does not keep spinning.

Channel distortions; defective cartridge / needle, wrong insert position. Swap the LP channels on the cartridge - is it not the fault of Radmor, its preamplifier.

Check the photoresistor for damage - they utilized themselves (if necessary, take pictures of it), the bulb must be functional - also with the voltage / power value.

bercik97 wrote:

Bernard doesn't keep turning.

marian1981.02 wrote:

And I would check or replace the F2 photoresistor and the bulb that works with it.

The problem is solved, I replaced the variable resistors responsible for the rotation from 10k ohms to 22k, and both photoresistors. Everything works, thanks for your help, I close the topic