I recently bought a cheap speakerset from TRUST, the sp-3100 (TRUST Soundforce 2.1 Speaker Set SP-3100).
Giving the cheap stuff the sound isn’t that bad, but the gear had the nasty habit of playing radio channells when idle or on low volume, RFI in a word….
Unfortunately the set doesn’t provide a radio at all; it just picks some stray radio station and plays it in the background, at fixed volume.
Today I decided to fix try to fix it, using some spare ferrites I had around.
DISCLAIMER: Read the Disclaimer and Copyright. Don’t follow the steps outlined below if you aren’t a trained technician. Always disconnect the gear from main and discharge power capacitors before operating. The sp-3100 operates at main voltages thus providing dangerous voltages inside. Check for dangerous voltages before operating! I will not be responsible for damages incurring following the steps outlined!
- Phillips screwdriver.
- A pair of ferrite clamps
Update (24/11/08): I silenced them, and not by throwing them out of the window.
Before opening I double check that the equipment is not connected to the mains in any way, of course. After that, I should take any care to discharge the capacitors inside the equipment!
First tried to ground the pcb (no avail)… the box is wood and grounding and the plug is two prongs…even grounding the pcb won’t help . Then decided to use all my ferrites.
The signal cable make one loop around a larger ferrite, as close as possible to the box. The mains cable is just inserted, and the tweeter cables are togheter inside a single ferrite.It’s now silent when idle…if I move cables around I can still hear Virgin radio, but very low. With properly placed cables No sound without signal…
- I disconnect the speaker set from the mains and operate the proper discharge/check procedures to ensure I have no dangerous voltages around while operating. I will not cover this as one must be a trained technician to repair gear running on mains voltage. If you’re not, stop reading here.
- I open the main box, unscrewing the the screws along the border. I don’t unscrew nothing else.
- I put a ferrite around the audio input cable, as close as possible to the pcb.
- I put the other ferrite on the mains power cable, outside but as close as possible to the box. This one may be rendundant as there’s already some stock ferrite around the power cable inside the set.
- I close everything again.
- I test before connecting to the audio source
This solved the radio interference for me
completely, although sometimes I still hear radio. The set is not completely silent when idle.