Re: Repairing Alesis M1 Active mk2 Monitor Speakers

After replacing U1 (U2 and U3 for good measure...) the monitor is operational !!!! Thank you for the infos !!! Great thread on those monitor.

Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Thank you Khron. Will order some from Mouser. I also found a low ESR cap for C8 that is 135 deg. I already installed a socket for U1. It just didn't made sense. Everything looks good. I desoldered Q1 to Q7 and tested them one by one. Everything seems ok but the chip wouldn't start. I'll replace the chip first and get back to you. Might take a while to get the chips due to holiday season.

Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Trying to repair Alesis M1 620. Replaced C6, C7, C8, C35, R3 and R4 and no reaction from supply. The fuse is not blowing, I have 320V between C6 and C7. Power on U1 is 10v between pins 5 and 7 and 1.9v between 5 and 8. I desoldered and tested all the transistors and they seem ok. Diodes also check good in circuit. Looks like U1 doesn't oscillate. Also checked R15, RT1 and RT2 after desoldering and checked ok. I checked U1 and I see a diode between 5 and 7 & 5 and 8. At this point I suspect U1. C8 replaced by a chemicon 330uF...