For Friday’s show, we used Alesis monitor speakers that we had in the lab, plus Steve, one of the students, supplied two.
During installation, one of the speakers started winking its blue power light and ceased playing sound, and before the show another did as well. Steve found a Studio Central forum post suggesting that the problem was due to a failed electrolytic capacitor that gets baked by a hot resistor right next to it, and a quick peek inside confirmed that it was a likely explanation and fix.
After unscrewing, the back panel lifts out and reveals the power supply board mounted vertically on a metal shield, and the crossover/amplifier board mounted flat on the panel.
The naughty capacitor, C8 (actually its replacement after I finished), is in the center red rectangle next to the offending resistor. Another bad electrolytic capacitor whose number I forgot to catch is featured near the top of the board. Both of these tested bad with my Capacitor Wizard in-circuit equivalent series resistance (ESR) tester; all of the other electrolytics on the board tested good.
It was simple work to remove and replace the two capacitors on each board, and it brought both speakers back to life. Thank you, forum posts and Capacitor Wizard!
BTW, are electrolytics supposed to look like this?
Two caveats about this repair. First, I should have used 105°C capacitors, but I could only find 85°C caps on short notice, so these will fail quickly and need to be replaced again. At least now it’s known exactly what needs to be done. And second, the forum post suggests moving either the resistor or capacitor to get them further apart, which is a great idea but which I haven’t done yet. I’ve been trying to think up a clever way to stick a little heatsink on a vertically-mounted resistor, which might be a better solution yet.
Eek. That’s more than a little alarming. I’ve fixed more than one monitor by replacing a bad power supply filter cap. It would be interesting to mount a thermocouple or thermistor and see how warm it gets in C8′s corner while the speakers are going.
hello.
Have the same problem with mine monitor. Where to buy this capacitor C8???
Thanks in advance.
wartex37, in the US I’d order from Digi-Key. In Denmark, I’m not sure what to suggest.
Do make sure you get one rated for 105°C. And be aware that the capacitor may not be the problem, or may not be the whole problem. This is a good start and may fix your monitor, but it may take more work, too.
Hello. Thanks for your reply. I’m almost 100% sure this is the same problem like you describe here? It’s doesnt cost me a more if i try to do like you have. Maybe my monitor would play after i did the same thing?
Do you have some link Digi-Key?
http://www.digikey.com/
Hello again. What is the exactly name of part’s i should search on digikey? Please name it both of them?
Thanks in advance.
Hello again. Sorry for disturbing, but woul like to know how to search for capacitor for MKll? On digikey when i search for capacitor comes a bunch of info with for capacitor. I’m not sure wich one i should chose? I’m not in to this, that’s why i would like if you can help me how to pick right one?
Greetings from DK.
wartex37, do you have any experience repairing delicate electronics equipment, particularly desoldering without damaging the circuit board and replacing polarized components in the correct orientation?
Honestly, if you’re not able to open your speakers, locate the capacitors I’ve indicated, and determine the correct replacement values yourself, I question whether you have the expertise to perform the repair successfully. And if you don’t have the expertise, you’re going to cause a lot of damage to the circuit board that’s going to take even more effort to repair.
I’m not sure I’m doing you a favor by helping you down this path. I understand you’d like to try the repair yourself and save money, but I’m not convinced it’s going to come out well.
It seems people forget that in most cities there is usually a shop that can repair TVs and stereos. I’ve had more than one monitor that I couldn’t fix(alignment issues and such) brought back by one of these shops. It’s usually pretty inexpensive.
Hello. No, i don’t have any experience with such kind of things. But i do know someone who can help me out. In other way, if we gonna blow out a hole thing the only way to get a new one is to speak with my wife.
You know, if i’m going to give my monitors away to one who knows how, it’s going to cost a new monitors, or something like that? If i should buy a new alesis there is nobody who can guarrante that would not going to happend again.
It seems people forget that in most cities there is usually a shop that can repair TVs and stereos. I’ve had more than one monitor that I couldn’t fix(alignment issues and such) brought back by one of these shops. It’s usually pretty inexpensive.
Yes, you have a right. I did speak with one of those. And you know what? I live in Danmark and 1 hour of any kind of reparations cost a money. The guy a have spoke with says, that would maybe going to cost me about 100 dollars. But he don’t know exactly what is wrong with my monitor.
Ouch. I would see if he’d be willing to look at it and give you an estimate for free. The charge I would expect would be no more than $40 or so. Mind, that’s the norm here in Canada.
Hello. Yes, maybe? But we are far away from Canada. I know what i’m talking about. Trust me. One Audi A4 a new one in Germany or Sweden cost about 15.000 euros. For this money i can get a used one, about 3-4 years old with 50.000 kilometers on a watch. You know, taxes here is killing a people… It’s double price for a used one. He’s hour price is about 120 dollars. He needs to pay a tax from it, about a half of price.
If i can get all this info wich one capacitor i need, i would appreciate a much? Sorry my english.
Wartex37, I honestly don’t remember the values of the capacitors, and I’d have to open my speakers in order to look and see what they were. Instead, why don’t you open yours and get the values off the capacitors you’re actually going to replace.
You’re looking for three things: A capacitance (labelled in μF), a voltage rating (labelled in V), and a temperature rating (labelled in °C). The easiest thing to suggest is that you match all of them exactly when you buy replacements.
Be aware of two things. First, this may not fix your speakers. There may be something else wrong and you may still need to take them to a shop. Second, without doing additional rework that I haven’t done yet, this is not a permanent repair. You’re just prolonging the life of the speakers; the new components, identical to the old, will fail in about the same amount of time as the originals did.
Keith, this article was exactly what I needed. I was able to fix my left channel Alesis M1 MKII monitor by replacing the C8 cap with a better one from digikey.
I watched some online videos about soldering and desoldering, and the pictures and info from your article did the trick!
Thanks
Jon, I’m delighted you found this useful!
Remember the caveats — it’d be better to move it further away from the hot resistor. Also, one of two speakers I fixed failed again during the first use, so it’s possible there’s more wrong than this.
Still, best of luck with your repaired speaker!
Keith, thank you!
I live in Albquerque, New Mexico and one of my Alesis M1 monitors has caught the blinking light disease. I’ve had the monitors for 3 years now and have never before had a problem.
I found another website that found these capsitors as the culprits and was able to get their speakers up and running again.
I have some soldering skill as I am a computer programmer who’s taken some electrical engineering courses that taught soldering, but I still want to find a professional somewhere to help me get it done.
I called some Radio Shacks in the area and they are clueless, as am I on where to go. Who did you call, and what kind of shops should I be calling. I’ll be glad to take some pictures and log my experience for reference for others as I believe this stuff is happening a lot now to other M1 Active users.
Thanks for the info!
ducthhazeone@gmail.com
Jesus, welcome! I was just in Albuquerque a few months ago and got some great shots of the computer exhibit at the Museum of Natural History — I need to finish editing those and get them posted.
I did the soldering myself — I do a lot of soldering, and have even soldered professionally, in a summer job long ago.
These capacitors are really easy to replace, as soldering goes. If you get a $5 iron and some flux-coated solder braid, and you know enough to order proper replacement capacitors and observe polarity, you can definitely do this yourself. I understand your reluctance — and normally I wouldn’t counsel someone to dive into a repair project if they’re uncomfortable — but if you have any soldering experience, this is doable.
If you would prefer to find a shop, I’d recommend checking the yellow pages, NOT for shops that advertise themselves as authorized repair centers for X brand, but for a place that just says they do radio/electronics repair, and they’ve been around for a while and they’re still in business. In the Wichita area, there’s a place called Red Baron that’s been around forever, and they know enough they don’t just do board-level replacement on whatever brand of TV they paid $2000 to get a certificate of authorization for. That’s the kind of place you want to find to be willing to do this for you (even though any of them that can solder could do it if they were willing).
Finally, my standard disclaimer — the capacitor failure seems to be very common, but it’s not necessarily the sole problem, nor even the problem at all. It’s possible that it won’t fix your speaker — but it’s most certainly worth a try.
Hey Keith I wanted to thank you for taking the time to share this information. The pictures were very helpful and having discovered this was a common fault I did not want to be a repeat customer for new powerboards at £45 a go, or servicing at £60 – plus 3 weeks waiting and cost of delivery both ways etc etc.
It almost makes you think that maybe Alesis are cynically selling poorly designed goods that will keep their repair techs in work for the next 20 years…..
Anyway – I fixed this with no drama. I went to my local Maplins (in the UK) and got a similar (had to get a slightly different μF rating because in the 105°C range the numbers were not an exact match, but I used a slightly larger capacitance so not a problem) and my repair bill was 50 pence instead of £50+
I now have 2 working monitors again
Cheers, Nick
Nick, glad that worked out for you!
Credit really goes to the Studio Central forum for finding and posting the original fix. But I’m delighted if the pictures helped, or increased your confidence in tackling it yourself.
Hey Keith, the pics were definitely what gave me the confidence that I could DIY this repair without blowing something up. I had also read some forum posts on the subject (probably the Studio Central one you mentioned) but having also seen the pictures I was sure it would be something I could tackle as an amateur. I also figured that at worst I’d end up sending it off for service after all.
Another thing I realised is that the hardest part of this job was getting through all the gunk Alesis puts over the screw fixings to release the PCB itself. I think replacing the cap was easier than a whole powerboard swapout would have been as the power input connector looked really hard to remove as it was sealed all round with more of that hard plastic glue stuff – so this really is the best solution to the problem in every way!
Thanks to all contributors to this fix
Argh! Looks like I have the same problem. I have the M1Active 620′s, and one died this week (no LED, just a ‘thump’ from the woofer when the power button is hit). I pulled my board, and the area around C8 is very heavily scorched and discolored. My Crossover board (dated 12/26/2005) looks a little different, between C51 and C56 I have what appears to be two heatsinks, but they’re screwed to a long (2+inch) pieces of (plastic? aluminum?) something. However, one has completely dis-attached from the board, not sure how to re-attach it. I’m afraid hot-glue will just melt again.
I’m going to try the C8 replacement fix, hopefully I can find one locally, and it will fix it. I’ll post back my results.
Thanks for everyone’s support!
Johnny, good luck with your capacitor replacement.
I’m concerned about your heatsinks detaching from the board. Do you have a blog where you could post a picture, or would you like to email me one?
Nick, in case you’re still watching –
The hot glue on the screws isn’t that big a deal; it pops right off of most of the things it’s attached to. I did have to cut it off of something or cut it into pieces, but it wasn’t painful at all.
Hey i have monitor one MK 2 speakers, and my right tweeters stopped working yesterday, so i thought maybe i had blown it, but i swapped the one from the right speaker and put it in my left and it works perfectly, but when i put the tweeter from the left (which works in the right)… it doesnt work, so what do you reckon the problems is?? Circuit board???
Thanx for your help in advance.
Hello,
I’ve literally just blown one of mine through accidental excessive noise. The LED is blinking similarly to how you described, could it be the same capacitor? I’ve a reasonable knowledge of audio electronics but have never repaired an amp before, will the problem be reasonably obvious (ie scorch marks) if I open it up and have a look or will I probably have to get the voltmeter out?
Thanks in advance,
Chris Risley
Eric, I don’t have any experience with the Alesis other than what I read on a discussion board about replacing the capacitor, which turned out to work.
From a logical standpoint, I’d say your diagnostic of swapping the speakers was good and your conclusion that the problem is with the board seems accurate, but I don’t know enough about the boards to suggest what to do next. I think you’re going to have to find a repair center.
If it were mine and I had time on my hands, I’d put a scope across the terminals of the failed tweeter and see whether any signal is coming through at all — might give a hint about the nature of the failure, whether it’s in the crossover section or the power amp, etc. But without a schematic or some obviously scorched components, I’d really be pretty lost.
Chris, if you’re handy with tools, by all means open the thing up and have a look around. The Capacitor Wizard in-circuit tester I use is a wonderful tool; but this capacitor was badly enough damaged, it was visibly obviously a problem. It’s inexpensive enough, if you can find a source for replacement high-temp capacitors, it’s worth trying just on principle.
Hi,
I have a pair of speakers Alesis M1 Active 620 and one time when i plug the power cord i listened a “clap” inside the speaker and it didn’t work since there. I opened the speaker and after test the power supply it didn’t had power on the output. I changed two transistors FET (IRF 840), two resistores of 39Kohm 2W and one zenner 20Volts (1N4747). It still not working! I think that the circuitry of oscilator is not working because i opened the other speaker which is good and on the same terminals of the same transistors IRF 840 the good speaker has an oscillating signal!
I don’t know what can I do, can anyone help me? Where can I buy a new power supply board for replace this???
Please help me, I need the speakers for work!
Thanks all a lot, best regards.
Pedro Madeira, from Portugal (email me if you can: djholtz@sapo.pt)
OK, I got around to taking some pics of the fried area around the capacitor and the detached heatsink: http://s116.photobucket.com/albums/o28/Uromastyx63/Alesis%20620/
I’m taking it in to the local electronics store to see what we can do about it all…
Wish me luck…
Pedro,
I asked a similiar question (parts, purchase a power supply board) on the Alesis website. I got an email back saying “if you’d like to order a part, please contact the parts dept @ 401-658-3131 ext 1407.”
Not sure if that helps from Portugal. If I end up having to get a new power board for mine, I’ll let you know how much.
–Johnny
Johnny, if you’re talking about the picture where the heatsinks were glued to the PCB and are pulling up, it suggests to me that something physical has happened to the board, but there’s no electrical reason that the heatsinks have to be in contact with the PCB.
Hi,
thanks a lot for both helps, tomorrow i’ll call Alesis and talk about the parts to know what can I do. If anyone knows something more, please tell me!
Thanks a lot for all,
Best regards.
Pedro Madeira
Hey folks,
I got my monitor back from the shop. The final assessment reads as follows:
“Replace broken connections in REG, circuit and in input jack circuit.”
Total charge was $30, and it seems to be working fine (left the power on w/ a sound source over night, no over heating or any other problems I could see/hear.
So, while somewhat cryptic , doesn’t seem to have been the capacitor issue.
Thanks for all your help, and I hope this info can help someone else.
(and a Thanks to the guys at Bailey Brothers Music in Montgomery Alabama)
–j
Hi,
Great walkthrough. I’d already tried this fix a few months ago but after I’d replaced C8, my fuse now keeps blowing as soon as I turn the unit on.
Any idea’s?! I didn’t replace R4, just C8.
Also, green component RT1, at the bottom of the board, just above the Alesis logo, seems to be unwell in terms of a visual check….I would replace it but have no idea what rating it is etc.
Thanks for all the info you have shared.
Gareth, I’m concerned about that fuse — usually a fuse blowing means something much more serious going on.
I don’t have any good pics of the board, and I don’t remember RT1. I have another speaker I need to open and fix, and I’ll take better pictures and notes next time, but it may be a little while.
Do you have access to a good service shop? I’m afraid it may be time to call the pros.
hi, i own the m1active 620′s.
recently during this winter cold my speakers were exposed to freezing temperatures in a room with no heat…
when i returned to finally turn on my gear one speakers light was blinking and producing some high frequencies clicks from the tweeters. the other worked fine for a short period that day then began to do the same thing. both wont produce audio just the blinking lights and clicky sound…
ive owned these for 2-3 years. maybe a local repair shop can fix it? do you think the cold might have had something to do with it?
Clark, two thoughts. First, electrolytic capacitors contain a semi-liquid electrolyte, and it’s plausible to me they could have been damaged by the cold. Second, at least in my part of the country, cold often brings low humidity — it’s possible they could have been damaged by static electricity when you were in the room or hooking them back up. I think the capacitors are more likely, though.
If you’re comfortable with tools, pull the back plate off and the guts out and look (just visual) at the circuit boards. The electrolytic capacitors are the little cans that I highlighted in my photos. They should be clean (or at most some non-scorched glue on them) and round, with no bulges and especially no bulging on the top. If they look otherwise, they’re probably the problem, and easy to replace.
If you’re trying out local repair shops, ask them whether they have an in-circuit capacitor tester. (Capacitor Wizard is the brand name I know of.) If they do, they’re in my opinion more likely to fix your speakers on the first try and with a minimum of hassle.
thanks for the help
ok so i have pulled the board out and noticed under r3/r4 there is a scorch. i dont notice the scorch under C8 but there is the black glue. should i replace c8, and both r3/r4? i may do it myself if i find the right parts online, though there may be a half descent electronic shop in my town that could do it, though i feel comfortable replacing it if i have the right parts
Clark, I’m guessing your speaker has slightly different part numbers than the one I worked on, and I don’t have a schematic, but it wouldn’t surprise me if R3/R4 run hot by design. Are they larger resistors, like the big one standing on end next to the capacitor in my photo? Slightly rougher texture, rather than smooth? If so, they can handle the heat, and your replacements are going to do the same thing anyway.
The “black glue” on C8 — is it scorched and nasty like in my capacitor closeup, or is it just black silicone RTV or something? I think the stuff on my capacitor isn’t actually all glue — I think some of it’s electrolyte that oozed out.
Sounds like C8 may be a good choice for you to replace. But if it has overheated and dried out its electrolyte, it’s fairly likely you have other dry capacitors, too. Arcade game repair shops tend to “shotgun” replace all the electrolytics in a monitor; although having tested all of the caps in these speakers with my Capacitor Wizard, I only found two that appeared to need replacing. Without the Wizard, I guess I might suggest you replace everything — the parts will cost you less than the shipping.
I don’t know how well you know your way around electronics, but I’d suggest:
Good luck!
Had the same issue, bought a basic soldering kit from RadioShack for $8 along with the $10 desoldering vacuum. Got the replacement capacitor from Fry’s (220uF, 35v, 105c rating) – about a buck. Once I had the board on my desk the whole thing took about ten minutes. I followed the article “how to desolder components” found here:
http://www.hardwaresecrets.com/article/164/1
I couldn’t believe how simple of a fix it was, I should have done this last week!
Can any one help with where to find replacment tweeters for the mk11 ?
Paid for some on e bay about a month ago but they were never delivered , the online store will not reply.
Hi,
I have just purchased some M1 MkII Actives on ebay (waiting for delivery), so have taken an interest in their various issues. I will be doing an overhaul of the electronics when I receive mine.
Keith, as you mentioned that you may try to add a heatsink to the hot resistor, I thought it worth mentioning that there are resistors available with heatsink mating surfaces, similar to TO-220 semiconductor packages. The board looks pretty tight though, so it may not be an easy swap.
The other thought I had, was to try to mount some components under the PCB. Again, the spacing looks fairly tight. It may be possible to mount a heat sink mating resistor underneath the board, screwed to the mounting bracket as the heat sink. I expect that would be a slightly fiddly fix, but may solve some issues.
Another note of general caution, I think it would be best to always use a limiter prior to the input of these monitors, such as included in most compressors, etc. Also, leave a decent amount of head room on the mixer outs. This matter doesn’t really relate to this topic, but there are plenty of people who have blown these monitors with some unanticipated analogue bass resonance, etc. Of course, most monitors will include robust limiting onboard.
Anyway, just some thoughts.
Cheers,
Oliver
Just thought I’d leave this note, I haven’t noticed it mentioned anywhere here.
I bought the replacement but I don’t believe this is the problem for me (damage was caused by excessively high volume distorted audio for a few seconds) although C6 (390uF, 200V, 105 C) seems to be the damaged one.
http://i143.photobucket.com/albums/r154/mister_riz/DSCF1427.jpg
I’ve been told if the top of the capacitor is domed rather than flat then it is a sure sign that it has blown or will blow soon. Off topic yes but I’m pretty sure people with a variety of problems with this amp will be drawn to this site and it’s worth mentioning
Will explain later if replacing this big boy fixes the problem…
hey Keith,
Thanks for the tip. I successfully repaired my faulty Alesis M1 MkII today. It cost me 1700NOK for a new PSU the first time this happened. This time I spent 5NOK on components. Quite a bit cheaper and much faster
-Bjørn
Bjørn, glad it helped! I hope the replacements hold up for a long time.
First one speaker and now i have the two speakers with the power supplies burnt!!!
Anybody know where can i buy a new power supplies for replace? Before, i will try use 4 notebook chargers with 18v on output. Connecting the 4 chargers in serie i can have symetrical 18v and symetrical 36v… I think that could be one possibility to safe my day…
If anyone can help me repairing the two power supplies, add me on MSN and with live chat we can try to repair it! My email is pedromig-l@hotmail.com
Thanks a lot
hi keith, not sure if you can help on this topic but I just got a pair of alesis 320usb active monitors with a built in audio interface. I was having difficulties getting signal from the interface so (in hindsight, foolishly) asked a friend to take a look. in his efforts he made the mistake of switching from 220v to 110v on the back whilst powered on and seems to have blown something. it seems the fuse (3Amp) blew in the power lead and also blows in any subsequent leads tested.
any idea if there could be a single component inside that could be replaced or if I should RTV?
Hello!!
I bought a pair of Alesis M1 Mk2 but the left blue led it’s off when monitor is on, I think that it’s a little problem to resolve. Anyone know how can I replace blue led? If anyone have pictures of speaker inside, please help me , I hope for reply…
Thanks, Tiago Barbosa