I recently acquired a Beogram 4002 turntable (Type 5501 with optical carriage position detection) for a complete technical restoration. The unit arrived without a dust cover. Here’s a picture of the Beogram right after unpacking:
Besides a number of loose parts that fell out when I opened the box, I was surprised to see that the cartridge was still mounted on the tonearm:
Fortunately, the MMC4000 cartridge had a small plexiglass guard in place, preventing any damage. I safely stored the cartridge in a Belover MMC storage box:
While gathering the loose components, I even found a small black box containing an MMC20CL cartridge!
Here’s the unit with packing tape removed and the platter in place:
The overall condition is quite good! The aluminum surfaces, wood veneer, and keypad are free of significant damage. Everything under the panels appeared to be untouched:
This Beogram is in great shape for a restoration!
Scattered throughout the enclosure, I found debris that indicated the transport lock bushings had deteriorated:
As is common with these Beogram models, the plinth guidance washers were also crumbling:
Also typical for these older 4002 turntables is that the adhesive used on the keypad assembly becomes brittle, causing parts to detach easily. In this case, the keypad itself was almost completely separated:
I noticed that the solenoid switch was missing a plastic tab (located on the upper corner that gets depressed to activate the switch) which allows the solenoid lever to engage the switch arm:
Luckily, I found the missing plastic piece while working on the unit, so I could repair the switch (details below).
After this initial inspection, I powered on the unit and pressed START. The carriage began moving, and the tonearm lowered onto the LP setdown point. The AC motor also showed signs of activity, all positive indications! However, when I tried again, the tonearm returned to its rest position after moving only a few millimeters. Subsequent attempts produced the same result – the tonearm wouldn’t reach the LP setdown point. This pointed to a control system issue, which I planned to address after completing my standard electronics restoration. I typically replace all known problematic components before investigating unusual malfunctions.
I started the restoration process with the tonearm lowering mechanism and the carriage system. Here’s the arm lowering mechanism as I found it:
I removed all the moving parts, along with the rods and spindle responsible for carriage movement:
Then, I carefully cleaned all the components:
After reassembly, I moved on to the main PCB. Here’s how it looked before restoration:
I replaced all the electrolytic capacitors, the H-Bridge transistors, and the AC motor driver transistors, as these are prone to failure. I also replaced the transistor that amplifies the record sensor signal and included a trimmer for precise bias adjustment. The RPM trimmers were upgraded to modern, 25-turn encapsulated units for stable and accurate RPM calibration. The restored board is shown below:
With the board out, I also replaced the two power transistors of the AC motor’s push-pull stage. These are the original TIP31 and TIP32 units, mounted to the chassis for heat dissipation:
They were replaced with new, higher-specification power transistors:
The solenoid transistor, typically a TIP41A, is another common failure point in these turntables:
Having replaced several of these transistors in the past, I’ve added their replacement to my standard restoration procedure. This one was replaced with a new, higher voltage rated TIP41C, which is likely beneficial as it drives an inductor:
The power resistor that limits current to the solenoid after activation is another problematic area in the solenoid actuator circuit. It can fail open, preventing the solenoid from remaining engaged. This resistor is the unusual-looking white component in the picture:
](