can you send pics of the part you need? Digikey and Mouser have many options. Do you have any more detail on the the type of pot it is? Single ? Resistance? Power?

I'm not a tech. Here is a photo of the pot from the 03D and the schematics sent by Yamaha when I asked the part number. Hope this is what you asked for. Thanks!

That helps. A dual 100k with keyed shaft. Can you take the knob off, it looks like a press on. If your not married to the knob style it’s easy to replace. Where are you located?

I'm not near my studio right now, but yeah, I'm pretty sure I can take the button off. I'm not married to its style, although I'd rather be able to keep it even if it costs me a bit more. I'm located in France.

Thanks, well I think I am too far away to help.... I am in Canada. If your brave enough to dissemble the unit and take some more photos I can help you find the best match. it would be good to know if the pot is PCB mounted or panel mounted. I am guessing PCB, you need to know the lead spacing and configuration to ensure you get the right style replacement.

Note that (oddly) the gain goes from +10dB fully CCW to -20dB fully CW. That determines which end of the pot is connected on the PCB to the signal input, and is not shown in the schematic, unless it's coded by the "(F)".

It's feeding a virtual earth, so it will be an antilog taper. That could be the tricky bit in locating a suitable replacement. The "C" after the 100K value is the American designation for antilog. In Europe, "C" denotes log. Ahhh, standardisation...

Thank you both for the help! I'll see if I can get some pictures, and I'll come back here.

Even better: I found the original part!

My repairer couldn't get his hands on it, and it is indeed unavailable in Europe. But it’s still available in Japan. YAMAHA MUSIC EUROPE GmbH's support gave me the contact of a third party company able to import it, specialized in the distribution of spare parts from many manufacturers. It's rather convoluted, but I should receive it in a couple of weeks.