This document details the refurbishment process of a Beogram 4002 (Type 5503) turntable with an AC motor. The unit was received from a customer in Oklahoma, and an initial evaluation was documented previously here.
Upon arrival, the unit was partially disassembled, revealing its internal components. One of the first tasks involved addressing a loose spring in the shut-off switch, which was successfully reinserted to restore functionality.
The restoration began with the carriage assembly. This involved cleaning and re-lubricating all moving parts. The carriage PCB was rebuilt with a new capacitor, solenoid resistor, and a white LED replacing the original incandescent bulb in the position sensor. The solenoid arm extension, often prone to cracks, was replaced with a 3D-printed part. A new rubber damper gasket was also installed to ensure smooth arm lowering.
Attention was then given to the damper-to-tonearm linkage, requiring the sensor arm to be detached from the carriage for cleaning and lubrication. A small copper plate, essential for lateral arm movement, was re-attached with epoxy after cleaning. Both arms were then carefully realigned to be parallel to each other and orthogonal to the carriage rods. Finally, the original, fragile carriage pulley was exchanged for a more durable aluminum replica.
The AC platter motor underwent a revitalization process. Following extraction from the unit, the motor was disassembled. The enclosure halves were then submerged in motor oil and subjected to a vacuum to draw out air and allow for thorough oil penetration.
Concurrent with the motor oil infusion, other areas of the Beogram received attention. The output board was removed, and both the output relay and its associated capacitor were replaced. As a preventative measure against potential hum issues, a switch was added to enable the connection of system and signal grounds, a common solution when pairing the Beogram with amplifiers using RCA inputs.
The main PCB underwent a comprehensive restoration, which included replacing all electrolytic capacitors, power transistors, RPM trimmers, and the sensor arm circuit’s high gain transistor. Two aging tantalum capacitors on the PCB’s copper side were also replaced. New reservoir and motor capacitors were installed, neatly arranged with a custom-designed 3D-printed fixture.
Next, the three incandescent bulbs were replaced with LEDs. The two bulbs within the RPM adjustment panel were replaced first. The bulb covers were found to be deformed from heat exposure, a common issue due to frequent 33 RPM playback. Beolover LED assemblies were soldered directly to the existing bulb terminals. The last bulb to be replaced, located within the sensor arm compartment, was also swapped with a Beolover LED assembly.
The plinth guidance washers, exhibiting typical cracking, were replaced with 3D-printed nylon replicas. A black washer was used at the front for aesthetic purposes, while white washers were installed on the sides.
The restoration process culminated in a series of meticulous measurements and calibrations. The motor’s AC signal was verified, confirming the correct frequencies for both 33 and 45 RPM. The tracking feedback was then fine-tuned, uncovering a crack in the sensor assembly circuit board that hindered tracking functionality. This issue was resolved by soldering two bridges. The sensor arm transistor’s bias was adjusted by replacing the fixed resistor with a 5MOhm trimmer. Following the platter’s reinstallation, sensor response was measured and found to be within acceptable parameters.
The platter arm distance was carefully adjusted, and the platter was leveled in relation to the arm’s movement. The floating chassis was then meticulously aligned to ensure the platter sat flush with the surrounding aluminum panels.
After these adjustments, the tonearm’s tracking weight was calibrated. This involved replacing the counterweight adjustment screw’s circlip with an M3 nut. The tracking weight dial was then calibrated for accuracy at 1.2g, the optimal weight for most B&O cartridges. The arm lowering limit was set as a safety measure to prevent the arm from being lowered onto a platter without a record in place, especially in cases of record detection circuit malfunctions.
Addressing a common aesthetic issue, the 33 RPM adjustment scale, exhibiting a wavy background due to heat damage from the original bulb, was replaced with a new white background using 3M white electrical tape, resulting in a pristine appearance. Lastly, the original, corroded DIN 5 plug was replaced with a new, all-metal version featuring gold-plated terminals.
A 24-hour RPM test using the BeoloverRPM device yielded exceptional results, showcasing the stability of the classic synchronous motor design.
With the restoration complete, the Beogram 4002 played flawlessly. The next phase of the project will involve integrating the Beolover Commander remote control system to preserve the existing keypad and installing a Beolover RIAA preamp. This internal preamp will bypass the output board, allowing the Beogram to connect to a wider array of modern amplifiers that lack a dedicated phono input, ensuring this classic turntable can be enjoyed for years to come.