Beogram 4002 (5503): Arm Does Not Drop Anymore - Repair of Broken Solenoid Switch

A fully restored Beogram 4002 (Type 5503 with AC platter motor) that I sold in April 2025 to a customer in California recently had to return to the bench due to a warranty call (all Beolover-restored B&O comes with a one year warranty that covers all functional issues that may arise): After pressing ON the arm would find the LP setdown point, but it would not drop. It just sat there silently over the spinning record.

I put the unit on the bench and had a look. It quickly became clear to me that the solenoid did not get enough power to strike. Since I was able to push the solenoid lever down and it would then hold I immediately suspected the solenoid switch. This switch connects the emitter of the solenoid transistor (0TR4) to ground during the initial activation of the solenoid. When the solenoid plunger is fully extended the solenoid arm hits the switch and disconnects the emitter from ground, forcing the current to flow through the 8 Ohm solenoid resistor 4R1 (located on the PCB under the carriage). This reduces the current in the coil that it does not overheat. In this case the switch was oxidized and did not make its initial ground connection. Hence the solenoid only received the 'hold current' through the resistor and therefore did not have enough force to overcome the force of the release spring and friction etc...

This picture shows the small PCB that sits to the left of the solenoid, which holds this switch:

The switch is under the wiring. After unsoldering the three wires that connect the board and removing/loosening the two screws it can be removed:

I replaced the switch with a new one:

It is generally not a good idea to just sand the contacts a bit when this switch fails. While it can restore function for a while it usually does not last. The reason for the switch failure is that the oxidation preventing coating of the contacts burns off after a sufficient number of activations due to arcing. Therefore, the contacts quickly re-oxidize when they are sanded and it fails again. This switch carries about 3-4 amps during solenoid activation and breaking this current can cause small arcs. This is probably the reason why B&O replaced this switch with a timed electronic current limiter in the later DC motor 4002s and the 4004.

After reinstalling the board everything worked normally again. I played a couple records without a hitch, i.e. this Beogram 4002 is ready to return to its owner.