This article details the refurbishment of a Beogram 4002 (5504) turntable. An initial assessment of the unit is documented in a previous post here.

The turntable, stripped of its panels and platter, appeared relatively untouched. However, evidence of previous work emerged later.

The restoration began with the carriage assembly, which was quite dirty. After disassembling and cleaning the parts, the platter motor and capacitors were removed for thorough cleaning. The motor housing, including the bearings, underwent an oil infusion process under vacuum. This process, typically used for DC motors, proved effective in removing air bubbles from the bearings, potentially addressing any knocking issues.

Next, the carriage PCB was rebuilt. This involved replacing the solenoid current limiting resistor, prone to failure, with a modern, higher-rated 3W version. The incandescent bulb illuminating the carriage position sensor was replaced with a white LED and a 3.3k resistor. If the “run-off-stop” detection fails post-replacement, adjusting the LED’s vertical position usually rectifies the issue.

A new rubber gasket was installed in the damper plunger to ensure consistent arm lowering. Additionally, the cracked plastic pulley was replaced with a new aluminum one.

The tracking sensor light bulb was then replaced with a Beolover LED-based assembly. The pivot point of the damper-to-arm linkage was cleaned and re-lubricated. This involved removing the sensor arm assembly, cleaning the adhesive residue, re-epoxying it, and then reinstalling it. Afterward, the arm’s parallelism to the carriage rods was meticulously realigned.

Attention then shifted to the electronics. The PCB’s two Ta capacitors were replaced with modern Al units. The TIP31/32 transistors, responsible for driving the AC platter motor, were preemptively replaced with larger TIP41/42 transistors for longevity.

Additional work on the PCB included replacing all electrolytic capacitors, power transistors, the RPM adjustment section, the sensor arm transistor, and its biasing resistor.

Next, the light bulbs illuminating the 33 and 45 RPM adjustment trimmers were replaced. The 33 RPM bulb cover and the white plastic background often suffer heat damage due to frequent use. The damaged background was replaced with 3M electrical tape. Beolover LED assemblies were soldered in place of the original bulbs.

The output PCB, located beneath the keypad, was then addressed. The output relay and the capacitor that dictates the relay’s activation time after arm lowering were replaced. The motor and reservoir capacitor section was rebuilt using a Beolover capacitor assembly. The reassembled motor, directly soldered to the capacitor terminals, was also installed.

The disintegrated transport lock bushings were replaced with 3D-printed Beolover bushings. These bushings are designed in two parts for easy installation. Similarly, the cracked plinth guiding washers were replaced with 3D-printed black replicas for a discreet appearance.

With the turntable reassembled, adjustments and tests were conducted. The sensor arm transistor bias was adjusted to achieve a 4V collector voltage. The sensor response to an empty platter was then verified, ensuring a sufficient amplitude to disable the arm lowering function.

During the platter and floating chassis adjustments, an unexpected issue arose. The motor shaft was misaligned, causing the pulley to obstruct the aluminum platter. The motor was disassembled, and the shaft was carefully repositioned.

After addressing the motor shaft issue, the remaining adjustments were made, including platter/arm parallelism, arm height, and floating chassis position. The tracking weight was calibrated using a digital scale for accuracy. The flimsy circlip securing the counterweight adjustment screw was replaced with a more robust square nut. This ensures that the calibration remains accurate during shipping.

The arm lowering limit was also adjusted as a safety measure to prevent stylus damage. Finally, the tracking feedback was calibrated.

A 24-hour RPM stability test was conducted using a BeoloverRPM device. The results indicated excellent stability, a common characteristic of AC platter motors.

The final step was replacing the original DIN5 plug with a gold-plated unit. However, this unveiled a wiring issue—the front and left channels were reversed on the connector. After correcting the wiring, the turntable was finally ready for testing.

The restored Beogram 4002, paired with a thoroughly cleaned record, produced exceptional sound quality. Future upgrades include a redesigned Beolover AC-motor compatible RIAA pre-amplifier board and a Beolover Commander remote control, specifically designed for AC motor compatibility.