This Akai MPC5000 had a lot of issues with it’s tactile switches. Many of them had been replaced before. Some weren’t even properly soldered in and caused a nonspecific feeling of pressure when operated. Some buttons did not work anymore at all. As a solution I replaced all of them.
The eight most left buttons did not work on this Behringer Polysynth. I was looking forward to dive into this one as I never played a Deepmind 12 before. When I heard the failure description I already had an idea, what the failure is. After opening the unit and removing the left circuit board it was obvious. The eight buttons were all connected to the input of a 74HC165 parallel in, serial out shift register. These chips are usually chained for more than eight buttons and if only eight buttons are dead, the chip is probably at the end of this chain. I replaced the HC165 and was really happy, that the problem was solved.
Beautiful cheesy organ. Analog sound generation with MIDI and registration memories. Mine had some problems. The string section was dead just two days after I purchased it but it was an easy fix.