As promised, here'ya go!!!
The pinouts of the M520 power supply are as follows:
1 & 2 : +15V
3 & 4 : +6V
5 : No Connection
6 & 7 : +18V
8 & 9 : 0V (c)
10 & 11 : 0V (d)
12 & 13 : GND
14 & 15 : -15V
16 : +48V
17 : 11V~AC
18 : 11V~AC
19 & 20 : -18V
*Notes: the pin definitions detailed with the "&" are pins that are seemingly tied together. It's probably a design to accommodate higher current levels.
*The pins 17 and 18 carry the same 11V~AC, but are seemingly NOT tied together.
*I got all this info out of the Tascam M512/520 manual, referencing the technical diagrams. There's not a lot of descriptive verbage devoted to the power supply section.
*ALSO, I do not know the significance of the (c) and (d) designation on the 0V(c) and 0V(d) in the diagram. As I'm from the 'puter industry, that often means c=(common/analog) and d=(digital), but I CANNOT guarantee that's the meaning of the (c) and (d) reference, in this case, as there's NO digital circuitry in the M520. (Maybe GFM, Beck, or other knowledgeable people can help on this point).
Good luck, and more power to'ya!!! Heh.
PS: If you're in the Los Angeles area, I'd consider taking an offer on my M520 & supply, less cable. No shipping. Also, I have a genuine
Tascam M520 service manual, extra, that I'd take offers on. I paid a good bit to get 'em, off Ebay, though, and I'd sell at no less than my cost, which I'd have to check the records on, to determine.