DO-IT-YOURSELF : Some Sound Advice to Fix Stereo Problems

If your stereo system suddenly starts humming, loses sound from one speaker, stops working altogether, or works so well it annoys your neighbors, you can often fix the problem yourself.

Here are instructions for easy repairs and information on when it’s best to get professional service.

A word of caution, however--unplug the stereo system’s power cord from the wall outlet before cleaning switches, plugs, terminals, jacks and manual controls and before working on any external component. Don’t open a sealed cabinet; the delicate interior parts should be professionally repaired.

If your stereo develops a low frequency hum, first tighten the terminal and jack connections. If the hum persists, other options to try include:

* Separate cables connecting the stereo components from the power cords (they shouldn’t touch).

* Make sure the ground wire is connected to the ground terminal, a screw on the back of the receiver.

* If that doesn’t stop the hum, you may have to attach the receiver’s ground wire to a house ground such as the metal screw on an electrical outlet cover or a metal pipe.

* To prevent hum, keep your stereo’s components close together, so that the connecting wires are short and neat. You can check connections quickly and there is less cable to tangle.

If only one speaker works when you operate the phonograph:

* Jiggle the dead speaker’s wire where it connects to the receiver.

* If no change occurs, switch the plugs that fit into the jacks on the back of the receiver.

* If the problem persists, turn the receiver’s program selector from “Phono,” “CD” or “Tape” to “FM Tuner.”

* If the speaker remains dead, the receiver is probably at fault. If both speakers now work, the problem is in the turntable, CD player or tape deck. Such repairs are best done by a professional.

* If wire-jiggling eliminates the problem, clean all terminals, lugs, connectors and jack plugs at both ends of the wire. Use fine sandpaper to remove corrosion from metal surfaces. Spray TV tuner cleaner (available at electronic shops) into all hard-to-reach contact points.

If your stereo suddenly stops working, but the receiver’s panel lights do not dim or go off:

* Your receiver may have speaker fuses or circuit breakers on its back panel next to the speaker connections. Replace any fuses with exact duplicates from an electronic shop. Or simply reset the circuit breaker.

If all of your stereo components stop working, find the receiver’s circuit breaker or fuse, usually on the back panel, and:

* Reset the breaker or replace the fuse with one of the same rating.

* If the blowout recurs, have the receiver professionally repaired.

If your stereo system is too loud for your neighbors, muffle the sound in the room where the speakers are with lots of padded and textile-covered surfaces, upholstered furniture and rugs, for example.