Popping Computer Speakers

[normalicy]

Hey all, I beat my head against the wall for like 30 minutes deciding which forum was right for this thread. So I hope this is the place.

I just got a set of Logitec X-530 computer speakers off of ebay. They are pretty decent, especially considering the price. However, they pop every time the heater turns on or off. I assume this is a power supply issue (capacitor?). Is there a way to rectify it with a simple modification. My other (Altec Lansing) speakers never made the slightest sound when I had them connected. Thanks for any advice.

[jaycee]

There's a number of ways this could be happening. The interference is either entering through the power supply, in which case some filtering such as an X-rated capacitor across the primary of the transformer may help, or through signal leads in which case the audio circuitry is poorly designed. If they are in a plastic case, that doesnt help either.

[normalicy]

Well, I'd prefer to start with the capacitor first (I may apply some foil to the housing just while I'm at it though). Suggested rating?

I suspect a power supply issue more than a signal issue, because I don't get any noise from anything else & the heater is 2 stories down from me.

[psychosteve72]

this is a common problem with pc speakers, but there are a few simple steps that may help, but to start some more info would help. are these a plug back/power brick adapter or direct mains to the speaker? if plug back, most of them are, what is it rated at? can you buy one with a better current rating? can you open the unit you have, if so see what the filter capacitor is rated at and upgrade to a higher uf rated one. making sure you can still close the box. or re box it and add the upgraded secondary cap and an inline mains filter, these you can find dirt cheap on e-bay. hope this helps some, steve.

[normalicy]

Mains to speaker (goes into sub-woofer where amplifier is located). So, I should just get a higher rated uf filter cap & run it in parallel to the current one or should I just dump the current one? Working on stuff that runs on AC isn't my thing.

[psychosteve72]

ok, can you open up the box? if not options are limited to an inline mains filter
Schaffner | Connectors | Electrical/Power | Power Entry Module | Schaffner Type FN92XX & FN32X Series |FN 9222-15/06
something like this,(us version may look different and you may find cheaper nearer to you) put it in a small box, cut off your plug strip back and solder to inline filter and just wire a new plug on the end (you will need the earth connection)

edit, make sure you stay safe with mains, but really its just wiring a plug!

[psychosteve72]

if you can open the box then yes a bigger uf rated cap, solder it in parallel with the one in there, and make sure the voltage rating is at least as good as the one that is in there already! as some kind of guide my 25w stereo pair has a pair of 6000 uf 35v caps at the power supply backed up with a pair of 1000uf at the each amp.
also if there is room and depending on the box design, the mains filter mentioned earlier can be wired in the box, maybe replacing the mains input socket there already?

[normalicy]

Well, I'm familiar enough working with mains to know the basics & safety. So no worries there. Just not familiar with the engineering/design of power supplies.

That said, I do have access to the circuit board (8 screws holding it onto the box & no plastic or shielding on it, other than what is necessary to hold it in place. I'll rummage around for some caps of high voltage/uf rating (not sure I have anything over 3300uf though) & let you guys know how it goes.