Re: Repairing Alesis M1 Active mk2 Monitor Speakers

I eventually gave up chasing around the board trying to find the problem. Switch mode power supplies are beyond my understanding so I just made a conventional transformer/rectifier/capacitor supply and squeezed it onto the chassis without too much trouble. Works fine now.

My parts list, if your interested from cpc.co.uk:
FF01549 **1 **9.25 ***50VA TOROIDAL 2X25V; Power Rating:50VA; **MCTA050/25 *********
FF01546 **1 **9.56 ***50VA TOROIDAL 2X12V; Power Rating:50VA; **MCTA050/12*******************
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Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Luigi,
You did well, have you got any ideas for my board? My 470 ohm resistor was good but R15 (.22ohms!) exploded so I replaced that using a wire wound res, is that okay? I also replaced 4 x 1n4007 diodes, 2x irf840, 1 x 330uF, 1 x 1uF, 2 x 390uF and the UC3842 ic and most of the smaller transistors. Last test it came on but only for about 20 seconds before blowing all the 1n4007 diodes again and the fuse. The heatsink was hot. Before powering on, I compared resistances with the other good board and couldn't find any anomalies....