Question about Alesis M1-Active MkII Main / Stereo Speaker
Hello, My Alesis M1 ACTIVE MONITOR amp circuitry board is ticking at Ac power frequency; which is also indicated by the LED flashing and the periods of sound loss. I think it may be the capacitors on the amp. Would be gratefull for some advice and guidence. Also i would be grateful for any links in reference to repair.
Posted by spurs69 on
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 critical (220 to 470 uF will do) but it should be a 105 deg. type, preferably at 50V.
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.
Replace the board and all screws and plugs before testing.
Posted on Nov 28, 2007
WoW man, that was awesome. I just changed the c8 capacitor and it became alive. My problem was the left speaker alesis m1Active 620, I just switched on the button then I notice the was a sound that looks like a rhythm on the tweeter along that rhythmic sound the blue light flashes or blinks "flickers" along the rhythmic sound, then I just opened my alesis and then looked at the power circuit board, I can see that right under the c8 and the R4 the circuit board was a bit black so I just changed my stock capacitor number 8 which was 330uF-105deg-35V with a capacitor 330uF-105deg-63V. And after soldering it to the circuit board I plugged it and it just sounds awesome. Thanx for the tips :-) Besure not to get the same problem though. When I soldered my new capacitor I used the whole leg length of the capacitor so that when the resistor beside it exposes it to the extreme heat the heat only get the leg of the capacitor not the whole body so be sure not to cut the capacitor leg incase you buy the one with a long leg like I did. It is going to prevent it from being fried by the resistor. Awesome I may have to do the same operation on my right monitor too I think, coz my monitors are plugged in to the 220V 24/7 even if am not in town. So Thanx everybody and this forum and specially rayhow :-) God bless and have an awesome day/night :-)
Had the blue light flicker of death. Fixed this issue with a 330uF 35V cap. Sounds just fabulous now. I did get the cap out of the radiant spell of the resistor utilizing the longer leads and insulator for the leads. I had 2 months left in my warranty but figured paying for shipping to Alesis and at least 2 weeks wait just didn't compare to the $2 I spent with a local electronics shop.
Kudos folks. I've been unemployed for 6 months after a layoff and was really bummed until I found this site.
Posted on Mar 13, 2009
I own M1 Active 620. I changed the C8 capacitor with a 220 microfarad under 50V 105 deg type, wich fixed the problem only with one monitor.
The other one is still warm when you put the hand on the back of the monitor, you feel it.
I have changed the resistor on the other monitor with a 47k ohm under 2w and it don't works. This resistor is bigger than the original and it's impossible to read the value of the resistor because of the thermal interface material ( which confirms this piece gets hot)
So i've done a measure with a multimeter:
The original R4 resistor on Alesis M1 active 620 is 2,5 Mega ohm. I don't see how it could work with a 47k resistor!!!
I will change the resistor with a 2,5 M ohm (under 2w?)and tell you if it's Ok
Posted on Nov 06, 2008
Woo-Hoo!!! I've have mine sitting in a box for over a year because I was tired of $100.00 repairs every time I lost power. (Mine stay on 24/7) I just fixed it in 30 minutes with a $2.00 part and that includes driving to get the part. I bought a few spares and replaced C8 with a 105degree 220uf 35v which is what was in there. Funny thing is it looks like it was replaced once before meaning I got ripped for a new PS and they just changed the known bad cap.
Found this great link to my problem and have joined to ask a supplementary question.
I have replaced both capacitors and R4. Still have exactly the same problem. The capacitors didn't look like they had failed, no burned spots or oozing, but that may not mean they didn't - I can't test them. I have tested R4 and it appears to have failed. Does this mean that there may be another failed component I need to replace?
I'm not incredibly technical - been many years since college electronics - but I can wield a soldering iron with a degree of competence.
Any help greatly appreciated.
Using a smaller capacitor would reduce the bass response on 'high power', the capacitors supply the extra current the peaks of the music like the kick require, without that extra current there isnt the power available to fully deliver those kicks - unless they had used an overrated power supply which can supply it straight off the plug but thats more expensive and wouldnt make them as much profit :P.
i used 440uF caps for C8, long as the voltage is the same its all good, and oversized capacitors can never hurt!
Posted on Sep 06, 2012
I changed out C8 and it did fix my problem, but The C8 cap in my M1 was a 330uf. I replaced it with a 220uf because it was that or a 470uf (all that was available). When I played the speaker I can hear a slight lose of bass response with the 220uf instead of the stock 330uf. It's enough of a difference that I'm getting another 330uf and changing the C8 out again. Sounds like I have the 1/2 space switch on.
I appreciate the help and information, but thought I'd add what my ear and eyes observed. Also the cap I bought had long leads and I manged to install it away from the resistors and accomplished getting the cap away from the heat without having to move the resistors.
Thank you rayhow for the information! Very helpful.
Posted on Sep 28, 2008
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I've got this Alesis M1 active 620, and got the same problem as spurs69. No sound just ticking and led flashing. Anyone out there with a solution? Didnt happen until warranty expired.
Hi i got the same problem with my Alesis 620 M1 active monitors as Spurs69.
No sound only ticking and the blue led flashing. Didnt happen till warranty expired. Can you help?
I ran into the same problem a few minutes ago. I originally posted at:
Just to add a little more info, a quick and slight whining sound is heard before the woofer "pops". The pop isn't as pronounced as it is when the speaker is properly working. No sound other than a slight click from the tweeter is heard. The LED pulses along with the click. After turning the power off, another, longer whine is heard from the woofer.
A possible solution was given at:
Before I break out the soldering iron, is there anything else I should look at? Any additional info that can be given would be greatly appreciated.
the same..blue light is flashing and the speaker don t work during few minutes.
just a hint... make sure that you correctly measured the resistor. Don't touch the leads while measuring. 2,5 MegaOhm might be the resistance between your fingers! These power resistors sometimes break too.
BTW, mine was orange-yellow-orange (34 KOhm), I measured 38k
I have the same issue here I think (dried out C8 which spread electrolyte allover the board...). Since several strips are burnt and the part of the board between R11 and C8 went quite dark, could someone take a picture of this part of the board (both sides) and upload them somewhere? I need to figure out how to fix the burnt strips, and also I'm not sure about the value of the resistor just below R11 (I think that should be R18, can't barely read)
Thank you in advance