Beomaster 1900 Type 2904: Capacitor Replacement Part 2 and Slider Control Repair

All of the electrolytic and tantalum capacitor replacement tasks are complete now on this Beomaster 1900 project.

The last board was the tone control and FM tuning board.

There are are only eight capacitors to replace on that board. Here are two before pictures.

...and here are the after pictures. Very straight forward.

The larger task on this board is the repair of the three slider controls (bass, treble and balance).
It is very common for these controls to fail on the Beomaster 1900. The failure is mechanical and involves the plastic slide that holds the left and right channel contacts for the respective control.

A small plastic tab that holds the metal contact in place breaks and the contact becomes free to move around. This results in faulty or no sound in one or both channels.

I noticed at least one loose contact when I did my initial assessment of the Beomaster. To be sure of the condition of all the sliders they must be disassembled and checked.

It is a good idea to label the slide controls as they are removed from the board.

Two small, metal tabs on the end of the control must be bent straight so the metal clamp/holder can release and allow the contact slide mechanism to be removed.

Here are all three sliders disassembled. I found three with broken contact mounting tabs.

The repair for this problem is best made using a repair kit from Martin Olsen. Martin makes a number of  accurate replacement kits for various vintage Bang & Olufsen components that he sells on his Beoparts website.

In this case the kit consists of three replacement (plastic) slider control parts plus some useful instructions.

I cleaned the metal contacts and slider areas with Deoxit (cleaner and fader lube). Then I reassembled the slider controls.

 

Next up are the lamp replacement tasks.