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How to Replace an Optocoupler in a Flyback Circuit

Flyback circuits are used in various types of DC-to-DC converters. DC-to-DC converters change one voltage level of DC to a different voltage level of DC. For example, a 12-volt DC to 24-Volt DC converter. Some call this a DC-AC-DC converter because the electronic circuit takes DC, converts it to an AC signal, and then back to a different level of DC.. These circuits use optocouplers to keep the signal electronics separated from the output voltage side of the converter since the output voltage is usually much higher than the signal voltage side of the circuit. Optocouplers are composed of a light emitting diode and a photoresistor encased in a single casing. They are designed to be replaced as one unit. Voltage spikes and short circuits can generate the need to replace an optocoupler.

Things You'll Need

Antistatic strap
soldering iron
Heat sink
Screwdriver

Instructions

- 1
  Use the screwdriver to open the circuit housing. Look for the optocoupler. An optocoupler is usually housed in a small rectangular box. Some have a casing that says "opto" or "optocoupler. " Once the optocoupler is located, look at how it is attached to the circuit board.
- 2
  Place the antistatic strap around your wrist and clip the antistatic wire to the ground wire of the circuit. This prevents any static electricity from damaging the circuit. If the optocoupler is pluged into the circuit board, simply grab it and pull it out, paying attention to how it sits in the socket. Take a new optocoupler and plug it back into the circuit. If the optocoupler is soldered to the board, then clip the heatsink onto one of the four wires between the optocoupler and the circuit board.
- 3
  Heat the tip of that wire until the solder has melted and pull up slightly on the optocoupler until that wire, from the optocoupler, is free of the circuit board. Move the heatsink to each wire before you heat it. This will keep the heat from damaging the optocoupler. Repeat this step until all four wires are free of the circuit board. Remove the old optocoupler.
- 4
  Set the new optocoupler into position and clip the heatsink to the optocoupler wire leads. Heat each wire until the solder melts enough to accept the wire lead. Move the heat sink to the next wire lead and repeat the heating process. Continue this process until all four leads are secured to the circuit board. Allow the solder to cool, remove the heatsink, and reinstall the circuit board cover.

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