Hello,
I have a broken drum-machine here that seems to work fine other than that i’m not getting any sound from it.
So i opened it up and found that there is no -10v present. thus far i removed and checked Q1, Q2 (npn), C8 and D3(zener) in the -10v dc - dc converter but all those seem fine. This leaves me with the little custom sumida coil/inductor/transformer T1.
There is no stock (or datasheet) for custom roland parts so i'm left with finding a similar part. To be honest i dont know its purpose so that makes it even harder to find a replacement if such a part exist.
Another option would be to bypass the dc - dc converter with a separate module, PTN78060A or a MAX765 based module or something from aliexpress. If i go this route I dont know how to implement the line after R2 (i-20 to IC30A)!
http://www.synfo.nl/servicemanuals/Roland/TR-707_SERVICE_NOTES.pdf (page 10 top left corner)
Thanks allot, Any advice is much appreciated!

Edit: I just isolated the -10v supply from the rest of the board and the readings are a bit different (+0.7v is 0v now). But the problem persists.