First post as well. Same pop & dark issue with Mark100. Sent power supply to TAP Electonics in California. Tech said my supply unit is now a paperweight. Bad news component involved can't replace, but Yamaha Japan working on solution, maybe have in a couple months. My piano bought in 1995. Have you had any progress on finding a solution to this paralyzing piano problem? I'm taking part to another music-electronic repair person soon, 2nd opinion, to see if there is an alternate solution working with the "dead" power supply unit. Will stay in touch!