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PostPosted: Thu Dec 14, 2017 1:00 am 
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Location: shenzhen, , CN
Hi to all, I hope it's not an off topic. :arrow: A few months ago the volume of the left speaker of my pair of low-cost audio monitors began slowly diminishing. Every day it seemed to lose a fraction of it's normal operating volume until the speaker became nearly completely silent. Since I bought these speakers last years, I noticed that the left speaker tends to run very hot. So, when the speaker began to die out, I assumed that the speakers were poorly designed and weren't built to withstand their own level of heat, and after a certain amount of time they broke. However, I wasn't sure about the cause. I thought it might have been that a solder joint might have weakened and broken or something like that. However, I thought back to an experience that I had before where my PC's video card made a loud crack and upon investigation, some of the capacitors on the PCB had broken open. This was my first experience with bad capacitors.

So, with that in mind, I thought to pop open my left monitor and check around to see if something was visibly wrong. And sure enough, I saw something that looked like two capacitors that had overheated (i think) and vented some of their fluids.

I'll admit that, while I'm interested in hardware and electrical engineering, my knowledge is much more limited than I would like it to be. I would love to try this repair/upgrade, but I'm worried about messing it up and winding up with a pair of non-working speakers (which, is only slightly worse than a pair of half-working speakers...).

Now, at this point, I've been able to identify a potential cause of the problem. But, I'm not sure what to do about it, or if I can even do anything by myself.

I know that there are places online where I can get replacement capacitors (in this case, it looks like the caps that were used were 4700uF/35v caps). But is this an easy D.I.Y. job for someone who is inexperienced with electronics and soldering, but is willing to learn?

Long story short: I think that I need to replace two capacitors inside my speaker system. The caps that were in there (4700uF/35c) broke too quickly for my liking, maybe due to overheating.

Is replacing these capacitors something that is relatively easy for an inexperienced person?

Do I need a special type of soldering iron or can this be done with a cheap hardware store one?

Also, would it be possible to buy replacement capacitors that are stronger/better/durable/heat resistant, instead of simply re-buying the same type?

Should I (or do I have to) replace the bad caps with new ones that are also 4700uF/35v? Or could I/should I replace them with something else? If i can repair and improve these at the same time, I'd like to. I'm not sure if that's possible though, as I don't really understand how capacitors work...

Finally, If I manage to remove the old capacitors, do I have to do something to remove the capacitor fluids that are all over my speaker's PCB? What can I do to clean that and is there anything I should know about that stuff?
Thank you taking time to read and provide advice, kynix.


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PostPosted: Fri Dec 15, 2017 7:59 am 
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Joined: Wed Jun 24, 2015 4:17 am
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Location: Fergus, ON, CA
first off, welcome to the group. There are MANY...well pretty much everybody else more knowledgeable than I.
But soldering is not difficult. I would say 30 watts is about right for the job. (not fully knowing what speakers are in question).
Lots of videos on YouTube to show you how to solder.
Experiment on some old parts first, THEN when you are comfortable do the actual speaker work.
I would recommend getting the best capacitors you can get within reason that are the same specs (4700uF/35c in your case)
Be sure to do BOTH speakers, not just the effected speaker, so they are somewhat equally balanced. Plus it would be a good time to inspect the other speaker anyway...it may have the same issues as well.
Contact cleaner 'might' get the old residue off. An old tooth brush and some light scrubbing should do it. Ovoid anything overly corrosive.
Hopefully somebody else will chime in to give more qualified advice.
Good luck.
Keep us posted.

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PostPosted: Fri Dec 15, 2017 8:19 am 
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Joined: Mon Aug 08, 2016 5:46 pm
Posts: 933
Location: Markham, ON, CA
I am assuming that these are powered speakers? Otherwise there is no reason for any heat in a speaker cabinet. Going under the assumption that the speaker is self-powered, you might want to refer this particular repair to a reliable technician. The money you might spend on parts, soldering iron, etc may be better applied to paying a professional to investigate the cause of the heat/failure. Unless the speakers are many years old, caps just don't blow. If there is an underlying problem with the amplifier unit, a simple replacement of the failed part will not fix the underlying problem. I have never seen a simple cross-over generate any sort of heat.

If these are passive speakers, then the above is less applicable. Capacitors are readily available on the web, and simple soldering (not involving circuit boards) is not difficult and well within the reach of the average person.


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PostPosted: Fri Dec 15, 2017 8:25 am 
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Joined: Thu Sep 22, 2005 4:25 pm
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Location: Hamilton, ON, CA
Your advice Alexander is sound.

It's not difficult, just take your time and (as Alexander stated) practice on something first.

It's a good idea, when soldering, to use a small fan to make sure you don't inhale old solder fumes - some of it was lead based. In fact, not a good idea to inhale any solder fumes, I use a fan all the time when I work with solder.

Take some pictures as you disassemble, that way you don't forget how reassemble.
Take some pics of the side of the capacitors so you can go to a supplier and get the closest match you can.
As prior mentioned, do both speaker - upgrading the type of capacitor is not a bad idea. I like to use Solen, I get them at "The Tube Store". Get as close to the rated uF, don't be concerned with the voltage rating, but - make sure you are buying the same type of caps that are in the circuit. Usually, they are "non-polarized" and can be installed in any direction. Polarized caps, on the other hand, need to go back in the same direction.

It's not a hard project, you will likely enjoy it and feel better about your speakers once you complete the work. I bet you'll think they sound better just because you did it! (nevermind that the caps are new!).

Don't forget, put on some gloves when you remove the old caps that have broken open. You don't want that residue on your fingers.


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PostPosted: Fri Dec 15, 2017 9:00 am 
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It's not a hard project, you will likely enjoy it and feel better about your speakers once you complete the work. I bet you'll think they sound better just because you did it! (nevermind that the caps are new!).

quote]

Funny how that works almost every time. :D

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PostPosted: Fri Dec 15, 2017 9:31 am 
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Location: Calgary, AB, CA
Normally when someone refers to capacitors in a speaker they mean the crossover circuit which separates the frequencies between the drivers. Crossover caps don't really get hot, and rarely fail outright unless they are really old or the speakers have been severely overpowered (and in that case, it's usually the drivers that fail first)

If the OP is referring to POWERED speakers, then they are actually referring to capacitors in the power amplifier within the speaker; this is something much more complex than replacing a crossover cap, and is probably best left to a professional. Even if the OP could correctly diagnose which capacitors are damaged (visual inspection is NOT sufficient) he will not have determined the actual cause of the capacitor failure which likely something else in the circuit.


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PostPosted: Fri Dec 15, 2017 10:21 am 
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Joined: Thu Sep 22, 2005 4:25 pm
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Location: Hamilton, ON, CA
We will have to wait for the opportunity to tell us if it's powered or not.

As for speaker caps, any cap with age can fail. The cap opens up, splits, usually with a pop because of vapor building up.

Average caps can last as little as 10 years.
Sometimes, 30 before failing.

It's not uncommon, I see it all the time. Even unused caps can fail.


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PostPosted: Fri Dec 15, 2017 12:06 pm 
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Joined: Wed Feb 27, 2013 8:43 am
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Location: Stratford, ON, CA
Hi,

After a careful reading of your post, I am going to assume these are powered speakers. alexander_x has given you good advice about soldering and about cleaning up your PC board. If these were passive speakers, it would be a snap to get a couple of replacement caps from suppliers like The Parts Connexion, or Solen and solder them in. But for a powered speaker it may be that you can visibly see that certain caps as blown, but there may be other issues lurking including the very design of the internal amplifiers. If it were mine and I was trying to repair it, I would buy a set of replacement caps for both speakers. In this instance, both the specification for micro-farads and the voltage rating will matter. Then I would ensure that any capacitors found in the power supply section of the faulty speaker's internal amplifier was shorted and was not carrying a voltage charge. Google about that for instructions. Then replace the bad caps you have identified in the faulty speaker's amp and see what happens using the better speaker as a point of comparison. Finally, if this is successful, I would replace the same caps in the better speaker's amp on the assumption that with time and heat they will fail.

Cheers,
David Neice

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PostPosted: Mon Dec 25, 2017 5:23 pm 
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Joined: Mon May 23, 2016 1:19 pm
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Location: Mississauga, ON, CA
As BuyBye88 suggested, its most likely a capacitor in power supply of powered speaker. Never seen 4700uF/35v in passive crossover... but, hey, I have designed some wacky crossovers myself :-)


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