Many stereo systems go along for years without developing any audible signs of trouble, but not all enjoy such immunity. When trouble does develop, it happens most frequently in one of six general areas, to which the serious stereo owner should pay special attention.

One such area is the phono pickup, which-even if nothing ever goes wrong with it - is bound to become dirty after a time. Dirt on the stylus creates distorted sound and hastens record wear. It should be removed with a gentle back-to-front whisk of a soft brush, very lightly moistened. Dirt lodged behind the stylus tip, between the cantilever and the bottom of the cartridge body, also should be removed carefully, since it interferes with the free movement of the stylus in tracing a record-groove.

Other points to be checked out periodically include the alignment of the stylus (you can do this with a strong magnifying lens), the correct amounts of vertical tracking force and of anti-skating, and the condition of the stylus tip (this requires a microscope). In the event of hum or signal loss on one channel, the first thing to inspect would be the connections between the cartridge pins and their four mating sleeves in the tone-arm shell.

Another often-neglected area is one's FM antenna and its related parts. Outdoor antennas are subject to the ravages of weather but even indoor antennas need periodic inspection. Look for corroded connectors, frayed wire ends, wire-wraparounds that have become loose - all these can degrade FM reception. Check too the correct orientation of the antenna with respect to the desired station's direction. If all seems well and you still pick up a lot of noise, it may be necessary to change from twin-lead to either shielded twin-lead or coaxial cable - check with your local dealer on this.

Older FM tuners invariably need realignment after two or more years of use. This is a job for the experienced professional technician armed with the proper test instruments - don't try if yourself unless you are technically qualified. Realignment often is indicated by a unexplained loss of stations when everything else checks out as okay. The newest FM receivers and tuners - those with "crystal filters" instead of IF transformers - do not require periodic realignment.

Another problem area concerns speakers. A speaker system that suddenly loss its highs could have a burned-out tweeter, caused by a sudden strong transient, or, more rerely, by simple equipment failure. More common speaker ailments often are traced to the connecting wires from the amplifier or receiver. Inspect the hookups at both the amplifier end and the speaker terminals. Make sure all wire strands are securely tied to their respective terminals. One loose strand of wire, touching an adjacent terminal, can cause loads of sonic mischief. The loss of several strands of wire, a common blooper when stripping insulation, can actually change the effective gauge of the wire and cause a loss of signal. If in doubt here, use a thicker-than-usual gauge of wire (say, no. 16 instead of no. 18) to allow a margin of safety.