How to Fix a Laser Pen

By James McIlhargey

Since semiconductors have become inexpensive to produce, laser pens have found themselves in the pockets of countless businesspeople, presenters and other professionals. Sometimes things go awry and a laser pen stops working properly. There are a few troubleshooting techniques and ways to fix the laser pen yourself, outlined below, which will save you the cost of going to a professional to have the pen serviced (or buying a whole new pen).

Things You'll Need

  • Laser pen
  • Spare batteries
  • Jeweler's screwdriver, flat head
  • Needle nose pliers, two pair
  • Multimeter

Step 1

Swap the old batteries with new ones. If that does not work, check to see that they are facing the right way. Laser pens typically use button cell batteries, which have a large surface that covers the sides, and a small surface that is only on the face. Whichever part of the laser pen battery compartment that has a spring, is the direction the smaller surface should face.

Step 2

Disassemble the laser pen by unscrewing the screws. If the batteries are not the problem, then there is something wrong with the circuit itself.

Step 3

Remove the internal circuit board. Once all user-removable parts have been removed, use the two pliers to pull the circuit board out. Be careful not to damage the circuit board with the pliers. While both are gripped, slowly and carefully rock the circuit board back and forth to loosen it. The one thing that will resist removal is the button located on the pen for activating the laser. Once this is freed, it is short work to remove the circuit board.

Step 4

Test the components. Make sure that there are no shorts or cuts in the circuit. If there is a short, it is likely that the semiconductor in the laser is destroyed. If there is a cut, then it should be easy to rewire the circuit to reestablish the electrical path. Should neither of those prove to be the case, then identify the small potentiometer. This is a component with a screw on it. Use the multimeter to measure the resistance of the pot. Also measure the direction in which the resistance is increased.

Step 5

Trim the pot. Turn the potentiometer to its highest resistance, and connect the batteries. While depressing the laser switch, slowly and cautiously turn the pot to lower resistances. Once you see any hint of laser light, stop turning. Then proceed at about 1/10 the speed, to try and turn it to the spot of peak brightness. If your laser pen is still not working, then it is likely broken beyond repair and you will need to replace it.

Tips & Warnings

  • Be careful to avoid static electricity while handling the circuit board. The smallest jolt could destroy the semiconductor.