Two of the indicator lights of the Beocord 9000 that I am currently restoring had issues. One had a broken off lead (REC CAL), which seems to be the standard failure mode of these bulbs, and the other (TIME CAL) had low intensity due to a partially evaporated filament.
I decided to replace these bulbs with SMD LEDs matching my current approach with these light in Beomaster 8000 units. This achieves long term stability and also makes the displays resistant against shipping damage. Unfortunately, the reflector cabinets of the Beocord 9000 are smaller than the ones in the Beomaster 8000, so I had to redesign my PCBs for the SMD LEDs. I made a short video about the process:
Here are a few additional pictures:
One of the bulbs (RECORD) has a different lead polarity than the other three. This needs to be taken into account for the LED replacements since LEDs are polar:
These are the circuit boards that I designed. I use high brightness white LEDs that I run with 1k resistors (1.2k achieves the original low brightness of the incandescent bulbs). We decided to go with a bit higher light output for the counter 7-segment displays, and so I matched the indicators. It looks much nicer this way if the room is lit or the sun strikes the unit, while it still does not 'bite' the eye if the room is dark.
This shows them in action without and with covers:
And here with the cover installed:
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