On the subject of the 2400.

What is the recommended bulb replacement?

5mm 12V/1W ?

Honestly ? I don't know.
I bought them as a 'Beomaster repair kit' and no markings.
Try do a search, lots of discussions about the lamps.

jesperb wrote:

Try do a search, lots of discussions about the lamps.

I know, and that is exactly why I am asking. A  consensus seems to be missing...?

I remember Dillen hinting at the original parts list as being wrong...

...i go my lamps from Dillen (too).

Got a little spare time, which immediately went into the Beomaster 2400 on the kitchen dining-room workbench (no room for guests this week).
Looking at the 'volume up mute' issue, where volume would play briefly and then mute for the first 3-4 taps on 'vol up', I measured out 'any and all' voltages around P3 and P5, all voltages matching the values on the diagram. Finally I gave up analyzing the muting diagram, couldn't quite understand it anyways and decided either 3TR3 or 3TR5 should go. Mainly just because they are both involved in muting and the diodes and voltages around them, had all measured out fine. 3TR5 (BC547B) out and in with a new BC547C and now 'volume up' works. Old BC547B tested out fine on the PEAK DCA-75 but the legs were 'rusty' so maybe just a 'tired' tranny 😳

Final issue left to fix : Loud hum in the earphones which disappear when i touch ground, so maybe a grounding wire desoldered itself somewhere? I see no caps left to recap in the signal path from tape-in to the headphone plug. No hum when playing on speakers. Voltage selector is at 220V.

I thinks this project is almost done. Did a FM tuner check yesterday, reception is surprisingly good, with only a short length of 0.75mm2 wire pushed into the antenna plug 😁

Only headphone hum left to fix. Tried two different jack-to-mini-jack converters and 3 different headphone types so an issue with the electronics.

Cannot find any shorts or loose ground wires, the Tape-In DIN plug is rock steady in place.
Hum increases when i touch the metal end of the electrolytic caps on the sound control board and almost disappears with volume down (=mute).

Not sure if that would be an indicator ? 

Will give it a final troubleshooting try and - even if the remaining hum will hurt - wrap it up.