My latest addition to the stereo system, an Onkyo Integra M-506RS amplifier, had a speaker # 1 bulb out. After removing top and bottom panels, additional four screws hold the front panel. Nice thing about this amplifier is that you do not need to remove the knobs in order to remove the face plate. It just slides off over the knobs.
After 30 or so years, the rubber boots which hold the bulbs hardened and are very brittle. You need to be careful removing them. Otherwise they will just break apart. Once the boots are removed, carefully pull the bulb out. Here is a picture of the old bulb (bottom) and new one (top) that I have bought from an AudioKarma member (dgwojo).
The replacement bulbs are 14V 80mA 4.12mm. I have done some measurements and my multi-meter reported 13.3V at the source with voltage dropping to 10.3V with load (tested with a working bulb). Once the bulbs were in the sockets, I had to deal with the brittle boots. I could have replaced them with a rubber grommets but I have decided just to strengthen them with super glue and wrap them in couple of layers of black electrical tape. Here is the original boot for the speaker lights (one is already removed):
Here is my super glue and tape treatment:
You can see above a small piece missing in the right rubber boot. That’s how brittle they are.
And here is a final assembly:
I have only replaced one bulb in my amp. The replacement 14V 80mA one produces the same brightness than the original one. At least I can’t notice any difference. This procedure was very easy. The only difficulty was aligning the face plate with the knobs. Somehow, there is a lot of play when you screw the brackets that hold buttons to the frame. But after some trial and error I was able to get a good alignment.