Let’s begin restoring the electronic boards. The main control board needs its capacitors replaced and the RPM relay (along with the RPM trimmers) need attention. Additionally, the output board requires inspection of its phono muting circuit. It’s worth noting that aside from wiring, the muting relay is the sole electrical part interacting with the phono audio signal. The turntable’s electronics mainly manage the platter motor, tangential arm, indicator lamps, and user controls, none of which are part of the audio pathway.

Here’s the main control board pre-recap. Notice the electrolytic and tantalum capacitors. Capacitors 4.7uF and above will be replaced with new 105°C Nichicon capacitors. For those below 4.7uF, I’ll use WIMA MKS polyester capacitors. While I prefer WIMA MKS for 4.7uF as well, their size makes them unsuitable here. Importantly, the 0.47uF 1C10 electrolytic capacitor will be upgraded to 10uF based on Beolover’s testing, which yielded optimal speed stability for this motor.

This is the main board after restoration.

Next, we have the output board before…

…and after restoration. A grounding switch has been added to allow for signal ground and chassis ground connection or disconnection, based on the user’s preference.

With mechanical parts cleaned and lubricated, and electrical components refreshed, it’s time for a test. As a safety measure, the tangential arm motor belt and platter have been removed to prevent unexpected movement if any issues arise. The arm position scale was also taken off the tangential arm transport for a closer look at the switches and position sensor lamp.

Upon connecting the Beogram to power, the main reservoir capacitor reads slightly above 30 VDC, which is positive. The fixed arm sensor lamp and the 33 RPM indicator lamp are both lit. The platter motor and tangential arm motors are running, an expected outcome since the position scale is detached, leaving the SO switch unable to turn off.

There’s one immediate issue: the tangential arm position sensor lamp is off.

Without this functioning lamp, the control logic cannot accurately pinpoint the location of the tangential arm assembly.

It has been replaced with an amber T-1, round LED.

This LED has a 591nm wavelength, 13000 mcd luminous intensity, and a 15° viewing angle. The key takeaway is that the sensor effectively detects the light and provides the correct voltage to the control circuit. A more thorough check of this sensor voltage will be conducted later during the service manual adjustments and checks.

Here’s the new position sensor lamp in place and operational.

Now’s a suitable time to pre-set the tangential drive tracking sensor. Disassembling the sensor components during cleaning means the tracking alignment likely needs recalibration. While visually centering the tracking sensor aperture was a reasonable starting point…

…fine-tuning is necessary. Using the aperture position adjustment screw, the aperture is set to allow the arm to pivot freely and prevent the tangential arm drive motor from unnecessary activation when the arm is lowered.

Next, the tracking sensitivity adjustment screw and aperture position are manipulated. The objective is to find a setting where the sensitivity screw effectively controls the arm’s forward movement when lowered. This ensures sufficient play in the tracking sensitivity screw for precise tracking adjustment later, during the service manual adjustments. Once achieved, the aperture position screw can be tightened.

Finally, it’s time to replace the original incandescent speed indicator lamps with Beolover’s LED board replacements—the final step toward optimal platter speed stability.