I recently bought a 24 channel Yamaha PM2000 mixing console for the studio, and I've been busy fixing it up and making modifications as needed. I'll add much more to this series of posts about the PM2000, but I'll start with a relatively simple project - replacing the incandescent bulbs with LEDs.
There are lamps in the lighted on/off switches on each channel, and in the VU meters. The original bulbs looked great, but many of mine were burned out, and aside from that they draw much more power than comparable LEDs.
The switch bulbs are nestled in behind the opaque channel on/off button, with everything wired to a little attached PCB. Removing the original bulbs can be tricky. They sit inside a little rubber grommet that holds them in place. The combination of time and heat has made the surrounding rubber fuse to the outside of the bulbs, so removing them required wedging a very small screwdriver in between the grommet and the bulb to get it loose. After it's out, it's just a simple matter of de-soldering its two wires from the attached PCB.
The other part that needs to be removed is the 820 ohm 1 watt resistor on the back of this PCB. It would have been nice to repurpose this resistor to set the current through the new LED, but there was no practical way to accomplish this, so you're better off just clipping it out and using a new resistor in series with the LED.
I soldered a 820 ohm 1/2 watt resistor (your value may vary depending on what type of LED you use) in series with the anode of the LED, extended the cathode with a few inches of wire, and covered both in heat shrink tubing. After squeezing the LED into the rubber grommet, it's just a matter of soldering its leads to the same PCB pads the original bulb was connected to. The cathode goes to the pad closer to the front of the switch, and the anode/resistor connects to the pad closer to the rear.
I used 5mm amber LEDs inside these switches. The color is pretty nice, although noticeably darker than the original bulbs. I would have liked to find a closer match, but I got tired of shopping around and settled for these.
Replacing the VU bulbs is a similar process, with a couple notable differences. You'll need brighter LEDs than you do in the switches, and the supply voltage is different, so you'll need to experiment with a different value for your current limiting resistor. The LEDs also get connected to existing flying wires instead of a PCB.