It is correct that the volume control is optical with a miniature bulb and LDR resistors sitting inside a
sealed housing on the main board.
There's one housing, one lamp and 4 LDR resistors. Two LDR's handle the volume, the other two handles loudness.
(Balance control is a sliding potentiometer under the large aluminum lid.)
If the bulb inside the housing burns, a safety circuit cuts in and the Beomaster will mute completely.
If you have sound from the Beomaster, we can rule out this lamp.
The panel lamps, however, is a different story. And they are in fact real lamps, not LED's or LED displays as some people think.
The only LED is the red standby indicator.
The volume indicator "arrows" on the panel are not directly related to the volume circuit but merely indicates the setting.
It's quite common to see strange behavior if one or more front panel lamps are burned and/or are of a wrong wattage, even
the lamps for checking the bass, treble and balance controls are important to give the right load and power supply discharge
effect when going into standby.
Some Beomasters will play fine but won't be put into standby without pulling the mains plug, others
will change channels intermittently or continously, others again will do other things.
Generally, the lamps are quite critical for correct operation in these wonderful machines.
I can supply a kit containing a complete set of fresh lamps of correct wattage (plus a spare).
The kit comes with (dis-)assembly instructions and will fit Beomaster 1900 / 1900-2 / 2300 / 2400 /2400-2
Soldering and basic electronic skills and tools are required to replace the lamps.
Martin