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Calling electronics gurus: help me fix this speaker/subwoofer set
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MonMotha:
Last setup I fixed with this issue had a volume bad pot (of all things).  Other problems I've had causing this kind of behavior are bad AC coupling caps, lifted/poorly connected ground traces, and bad connectors.

I presume you've tested this with various sources and all exhibit the same problem?

Do you have a scope?  A very effective method for finding the problem is to put a nice pure sine wave in at a reasonable amplitude and probe around until you see something that isn't a sine wave anymore (clipped, tons of added harmonics, etc.), following the signal path.  You can accomplish something similar by probing around with a speaker attached to a high-impedance amplifier, listening for when it starts to sound bad.
SirPeale:

--- Quote from: MonMotha on April 25, 2007, 02:15:02 pm ---Last setup I fixed with this issue had a volume bad pot (of all things).  Other problems I've had causing this kind of behavior are bad AC coupling caps, lifted/poorly connected ground traces, and bad connectors.

--- End quote ---

Bad pot - maybe.  Too bad I don't have one I can swap in quickly to test.


--- Quote ---I presume you've tested this with various sources and all exhibit the same problem?

--- End quote ---

Actually, no.  I'm sure my source is clean (my computer).  This is a speaker set I got out of a dumpster.  I'm sure this is why it was there.


--- Quote ---Do you have a scope?  A very effective method for finding the problem is to put a nice pure sine wave in at a reasonable amplitude and probe around until you see something that isn't a sine wave anymore (clipped, tons of added harmonics, etc.), following the signal path.  You can accomplish something similar by probing around with a speaker attached to a high-impedance amplifier, listening for when it starts to sound bad.

--- End quote ---

Nope, no scope.
AlexKidd:
Two diagnostic techniques that are easy are to turn it on and turn the volume up a bit and start tapping on parts of the board with a non conductive probe of some sort, maybe the plastic handle of a screwdriver or something. See if tapping on anything affects the static. If it does then whatever you are tapping on could be bad or have some bad solder joints. The other technique is to use freeze spray and spray it onto different components on the board and see if that affects the sound at all.

A burnt up resistor would cause those symptoms although usually those are pretty easy to spot because they are blackened or brown and the board is sort of burnt around them. Tapping or freezing those will affect the static too usually. If you had a scope you could look at the signal at different points along it's path and see where it is getting distorted.
ChadTower:

I'm sure you did, but just in case, did you swap out the wire harness(es) to make sure it's not something in there instead of the speaker itself?
MaximRecoil:
Are these PC speakers? If so, have you tried them in a different PC? Sometimes the problem is with the sound card, or more specifically, the soundcard's female 1/8" miniplug input.
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