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Saturday, July 15, 2017

Beogram 4004 Type 5526: Tonearm Lowering Damping

The tonearm lowering on the Beogram 400x turntables is accomplished by a solenoid that engages/disengages per an electrical control signal. When the solenoid engages, the tonearm is free to lower. To prevent a straight drop of the stylus onto the record there is a damping piston that slowly lowers the tonearm.

On these Beogram 400x turntable restorations we always service the arm lowering mechanics to make sure it is operating correctly and continues to operate correctly.

This picture shows the arm lowering components before I worked on them.

There are just four screws to remove and two springs to detach in order for the arm lowering damper to be removed for service.

There you have it. The Beogram 4004 arm lowering mechanics removed for servicing.

The damping piston valve control is opened up (I remove it) and the piston pulled out of the tube.

Everything is wiped down then lubricated again before re-assembly.

Here are the lowering components re-installed. Pulling on the solenoid engage lever manually allows me to check the piston control valve and adjust it so the tonearm lowers to play position in about one second.

While the tangential arm components are removed from the chassis I will do more cleaning and lubricating. I will also change out the stationary arm lamp and sensor with the custom Beolover replacement part.

Before I get to that though, I was not completely happy with the installation of the optional phono grounding switch on the output board. A nice thing about having pictures to document a restoration is that I can review them and evaluate the results of my work.

On this Beogram 4004 output board I felt the need to use hot glue to secure the optional grounding switch. Without something to secure it the switch was wobbly. The 1M ohm trimmer resistor on the board takes up too much space to allow me room to install the switch the way I would like.

You can see the glue doing its job in the above pictures. Not horrible but I don't like the look.
I decided to go back and rework this installation. I changed out the 1M ohm trimmer resistor with one that has a smaller footprint (setting the resistance value to what the original setting was).

The new trimmer resister gave me enough space to install the switch better so that I don't need any hot glue. As you can see below the black hot glue peeled right off and is gone now. I like this version of the installation much better.

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