Repair bad capacitors in computer speakers?
 

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 in 2010, 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.

[snip]

Site Staff edit: We were duped by a spammer from China.

The original post is here: https://electronics.stackexchange.co...speaker-system

It's bad copy/paste, which is why the post was nonsense after the first paragraph (all replies from that page posted as a single post). He tried to insert link for kynix.com (enjoy that link!), which is now deleted.

"Low cost" audio monitors may not be worth fixing. When all is said and done you have invested more money and time in what will remain "low cost" monitors. Suggest you seriously consider getting better monitors if they are important to your listening.

Have you tried to obtain the circuit diagram for the speakers? It will help understand what is going on in the circuit and in the repair process. Circuit diagrams can be downloaded from several sites, but many charge a nominal fee. At one time some brands included the circuit diagram with the user manual.

You should use the same mfd capacitors and the same or a somewhat higher voltage rating. A higher temp rating is OK, a lower one is not. Cheap monitors likely used cheap caps, so finding better should not be difficult.

Electronics supply houses offer circuit board cleaning materials that should do a good job, and they can be ordered online. The electrolyte may be corrosive so cleaning it off is a good idea.

Soldering PC boards is more about skill than the specific iron you use. A more costly iron is generally better for production work/frequent and continued use. For the occasional job a low cost will work. However, important are the soldering tip size and watt rating. Too much heat can cause damage to components, the board, and delamination of the copper traces from the board. Too little can result in poor joints and more time for components to overheat.

Hi Vivitern

Your left speaker is running hot? Rare. Sound Quality OK? Fuzzy sound could indicate a burnt voice coil.
If your speakers are ok and you like them then worth fixing. You can ohm out the voice coils individually as a test of their viability. expect 8 ohms typically printed on speaker magnet and similar speakers should have same resistance.


Here you mention a crossover. Speaker cabinets that have more than one speaker such as tweeter and woofer are never built without some kind of crossover.

If your crossover is merely a bipolar cap feeding the tweeter then they truly are cheap speakers as any self respecting crossover has an inductor to limit (choke) the high frequency to the big speaker and save that energy for the tweeter.
middle quality crossover is three way dividing the frequencies up into three bands. Adjustable bands sometimes.

All that said, you could proceed as follows. take the speaker apart and see what you have, Check your voice coils. draw a schematic or download. troubleshoot your crossover and repair or just upgrade your crossover with a good one that you can purchase in kit form.

here is a cheap example I would buy better but you see the cost is not that much.
https://www.ebay.com/i/172133859672?chn=ps&dispctrl=1


If you get a good crossover you could use it on your next set of good speakers

oh yea make sure you dont have a dc offset coming from your amplifier

BTW, what make/model are the monitors you have? What was their cost new?

From your description they sound as though they are self powered with the amplifier mounted in the left speaker cabinet, which could account for much of the heat.

Unless it's a pair of Reference or near-Reference speakers (like my Monsoons), then I'd never bother to repair them. It's so much easier to just grab a paid of decent speakers for under $50, maybe even under $25,from Amazon, Newegg, or even Walmart and Best Buy.