Yesterday I finished the repair of an old Moog Micromoog. The S-TRIG input didn't work and my initial though was that it probably would be rather easy to fix. However, it turned out to be more difficult to fix than initially expected. One of the first things I discovered when measuring the trigger-oscillator of the keyboard circuit was that one of the opamps was faulty. I replaced the opamp but the problem with the S-TRIG input still remained. To my surprise the problem got even worse since the keyboard also stopped working. I started to troubleshoot the keyboard circuit and discovered yet another bad opamp. I replaced the opamp and tested the synthesizer once again with no luck. After approximately one hour of troubleshooting I slowly begun to suspect that the new opamps didn't work either. A quick check revealed that both of the new opamps was bad so after I replaced them once more the synthesizer finally started to work as expected.