Is your TV picture or sound not what it should be? Here are some simple checks to make before calling the TV repair technician:

- If there is no picture, sound or light, make sure the set is plugged in. Then test the wall outlet with a lamp you know is working. If there is no power, replace the fuse or reset the circuit breaker in your home's main electrical control panel. Also reset the TV circuit breaker, if there is one, on the back of the set.Check connections and wires. Unplug the power cord and examine it for signs of broken insulation, burn marks or loose prongs at the plug.

- If the picture is not what it should be, look for the adjustment knobs and screws on the front and rear panels. Most are for correcting picture problems and should be used as instructed in the owner's manual. Allow the set to warm up before making adjustments.

- If the picture is constantly grainy on a set with a mechanical channel selector, jiggle the turner knob. If the picture clears, unplug the set. Remove the channel selector knob. Spray tuner cleaner (available at electronics supply stores) through the opening. Replace the knob. The picture may be distorted for about a half-hour afterward.

- If you have a roof antenna and your TV reception is poor, check out the problem by hooking up a set of indoor rabbit ears for comparison. If this improves reception, you know the roof antenna is the problem.

Check the lead-in wire that connects the antenna to the TV. Loosen and then tighten the connections at the set, at the signal splitter (if you have your FM radio or a second TV connected to the antenna), and at the antenna.

- Twin-wire antenna lead-ins often become loose and drooping in their projecting standoff brackets. When the lead-in flaps in the wind, the TV picture flip-flops and color fades in and out. Make sure that this wire is fitted snugly along its entire length.

- CLEANING TIPS:

Unplug the TV set before cleaning it.

- Let the set cool before cleaning the face of the picture tube. Spray the face with a commercial glass cleaner and wipe it with a soft cloth.

- Except for the TV screen, avoid using spray cleaners directly on the set. You may damage the wiring or clog the ventilation or sound-producing holes. Instead, spray the cleaner onto your cleaning cloth.

- TV cabinets are usually made of plastic or wood veneer.

Clean plastic exteriors with mild soap and warm water, using a cloth wrung nearly dry to prevent drips. Dust wood veneer cabinets frequently with a soft, clean, slightly damp cloth. To clean metal cabinets, chrome or any other shiny trim, use a soft cloth moistened with a bit of rubbing alcohol, white vinegar or window cleaner.

- SAFETY PRECAUTIONS:

- Unless you're skilled in electronic appliance repair, never remove the back cover of your TV set or perform internal repairs. An error in reassembly might cause radiation to escape or a fire hazard. Moreover, touching parts inside the set might cause a severe shock, even with the power cord unplugged.

- The power cord plug of some sets has one prong with a widened tip. The wide prong is meant to fit only the wide, or neutral, slot of the wall receptacle. Never file the wide prong down or try to plug it into an extension cord or plug rather than the outlet.

- Don't block the ventilation slots in the cabinet or place the set near a radiator or in a small, enclosed space.

- If the cabinet is damaged, there may be a shock hazard. Have a trained technician examine the set.