So, I recently purchased an MT32 and a Roland SC7 and I'm totally blown away by the sound quality, but I'm trying to use the SC7's mixer capabilities to add more flexibility to my setup, and it appears that the input volume pot on the back of it is broken. It just turns all the way around and around and doesn't do anything. Its also quite wobbly. I opened the unit up to look at it more closely and it looks as if it may have gotten jammed in at some point as the plastic rear portion of the pot no longer stays tight against the metal front. Even when I hold them together and get it to where it at least stops when turned fully in either direction, it still doesn't effect the input volume. It has broken in such a way that the input level is very low, so that input is nearly inaudible.

I'm not that savvy when it comes to potentiometers, so I'm having difficulty finding a replacement. I'm finding lots of similar things, but none that fit all the criteria.

The markings on the pot are:

(on the top)
Et
50 3B

(on the sides)
Japan
ALPS

From what I can deduce, this is an Alps 50kohm (I think) pot, with a 3B taper (which I believe indicates that it is a log or audio pot, as opposed to being linear... though this is all foreign to me). The body is 9mm wide by 12mm tall and the shaft is 12mm long by 5mm in diameter. It also doesn't seem to have a detent (center notch, like you would find on a balance control).

The thing that is really throwing me for a loop is that it has 5 pins plus 2 stabilizers on the bottom. All the ones I'm finding either have 3 pins or are called "dual gang" and have 6.

I've attached some pictures. I don't really need an exact replacement, I just want it to work properly... preferably without having to come from China for $20.