You enjoy listening to vinyl records, but unless your turntable's speed is accurate, the music's pitch will be off. Some turntables have a built-in strobe light that illuminates a pattern on the platter's edge and tests the turntable's speed. If your turntable lacks this, you can make one from a few dollars' worth of parts. The strobe uses a neon lamp that flashes with the standard U.S. power-line frequency of 60 Hz.
- Skill level:
Things you need
- PVC tube (half-inch diameter)
- Plastic pipe cutter or hacksaw
- Miniature 120-volt, 1.2-milliamp neon lamp with leads
- Diagonal wire cutters
- 100K-ohm, ½-watt resistor
- Lamp cord with two-prong AC plug and inline switch
- 30-watt soldering iron
- Electronics solder
- Assorted heat-shrink insulation
- Electrical tape
- Hobby knife
- Hair dryer
Cut a 5-inch length of PVC tubing (half-inch diameter) with the pipe cutter or hacksaw.
Cut the leads of the 100K-ohm resistor to a half-inch in length with the diagonal cutters. Trim the leads of the neon lamp to a half inch. Cut two snug-fitting pieces of heat-shrink tubing about 2 inches long and slip them onto both of the lamp cord's end wires. Solder one end wire to one of the resistor's leads.
Overlap one neon lamp lead onto the free resistor lead and solder the two leads together. Solder the free lamp cord wire to the remaining neon lamp lead.
Slide the heat-shrink tubing pieces up so that they cover the exposed resistor lead and neon lamp lead. Turn the hair dryer on to high heat and use it to shrink the tubing until it is tight on the leads.
Insert the neon lamp, resistor and cord into the PVC tube and slide it through until the end of the lamp barely sticks out of the other end of the tube. Wrap the end of the tube and the dangling cord with several inches of electrical tape. This will keep the assembly inside the tube.
Plug the lamp cord in and turn the switch on. Aim the light at a stroboscopic turntable disc or platter pattern to see if the turntable's speed is accurate. If the pattern appears still, the turntable speed is accurate; if it moves, your music will be sharp or flat.
Tips and warnings
- Download and print the strobe discs listed in the Resource section. Place these on your turntable and use with the strobe light to test your turntable's speed.
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