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Alesis M1 Active MK2 repair - Flashing Blue LED FIX





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Uploaded on Aug 18, 2011

Read description for step by step and links below.

Sorry for the poor image, done on my old phone years ago, but it will show you how easy it is to fix, read below for full details.
Updated and detailed video by rtcmanga
Hi Res Photo here : (thanks to Tomo Sombolac Music )

FIX for Alesis M1 Mk2 and 620 & 520 models

The flashing blue LED and loss of sound on the Alesis
M1 powered monitor is caused by failure of capacitor
C8 (220uF, 35V) on the power supply board.

It dries up due to its proximity to resistor R4
(47K, 2 W) which gets very hot.

This is a design fault.


Remove the power supply board (4 corner screws and 2 mains connector screws)
and disconnect the two plugs.

Carefully desolder C8 and replace it. Its value is not extremely critical
(220 to 470 uF will do) but it should be a 105 deg. type, preferably at

Remove R4 and replace it with a similar resistor with its leads bent so
that it is nowhere near C8, otherwise the fault will return. One end may
be connected to one of the existing R4 solder pads (furthest from rear
of board), and the other to the top end of resistor R3. Check that you
have connected it correctly by inspecting the PCB tracks.
It was recommend to us to replace C35 (1uf/50v). We did not do this, and can not see what advantage it has..

!!! Replace the board and all screws and plugs before testing.!!!

that was all that was needed. we pushed the existing C4 away from the new C8 capacitor in both speakers . It was an easy fix. If you know how to solder and de-solder, you can do this. I could have done this as a newbie, but my brother is more skilled and I was happy to let him take the blame if it screwed up! ;)
Seeing someone do it, its a lot more simple than i thought.

Just thought Id mention this, my right speaker failed after 8 years. I normally keep the power on at all times as I feel switching them on/off each day is more harmful. To support this theory, I switched off the power on the left speaker and waited for the parts to arrive. When I switched it back on 5 days later it too had failed, in a way it was a good thing getting them both done at the same time.
The first time I got the flickering LED was during a storm and right speaker failed, I left it off for an hour, an then it was fine.

Then when the speaker finally failed was during a resent power cut. So even with power surge protection these speakers are still vulnerable to spikes. This includes the later 620 & 520 models so I have been told. In one way leaving them on might make them last, but in another they are likely to face spikes. I always turn them off in a storm, or if the lights are flickering. Great speakers, shame about this design issue. I hope now to get at least another 3-5 years out of them. Who knows maybe they will go on and on now the components are further away from each other!


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