Finally got the Juno-60's chorus board out today. The MN3009 BBD chip tested fine on the multimeter, but the chorus sound was thin and crackly—classic signs of failing tantalum caps. Sure enough, C6 and C9 (both 1µF, 10V) were reading way under spec; one was barely holding 0.1V instead of 10. Replaced them with fresh 1µF tantalums, and the chorus is back to its thick, swirly self.
While I had the board open, noticed the patch memory battery: a soldered-in NiCd cell from ~1985, swollen like a balloon. Cut it out and installed a CR2032 holder instead. Simple fix, but I didn’t find a clear photo guide for this board revision online—so here’s a heads-up for anyone else wrestling with that particular Juno-60 revision.