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Gossen Luna Pro Battery Diode Update
The Gossen Luna Pro is a classic light meter that has been used by photographers for decades. It's a reliable and accurate meter, but one of its drawbacks is that it uses a 1.5 volt mercury battery, which is no longer manufactured. This means that you can't use the Luna Pro with modern batteries, and it can be difficult to find replacement mercury batteries.
Fortunately, there is a simple update that you can make to your Luna Pro to allow it to function with modern 1.5 volt button batteries. This update involves replacing the original diode with a new one. The diode is a small component that regulates the voltage from the battery to the meter's circuitry. The original diode is designed to work with the mercury battery, but it can't handle the higher voltage of a modern battery.
By replacing the diode, you can ensure that the meter will still function correctly with a modern battery. The update is relatively easy to perform, and it will allow you to continue using your Luna Pro for many years to come.
Parts You Will Need
- Gossen Luna Pro light meter
- 1N4004 diode (or similar)
- Soldering iron
- Solder
- Desoldering braid
- Small screwdriver
- Tweezers
Instructions
- Open the Luna Pro's battery compartment. The battery compartment is located on the bottom of the meter. Remove the battery cover using a small screwdriver.
- Locate the original diode. The diode is located on the circuit board. It's a small, black component with two legs. The diode is usually marked with a band on one leg.
- Desolder the original diode. Use a desoldering braid to remove the solder from the diode's legs. Once the solder is removed, you can gently pull the diode out of the circuit board.
- Solder the new diode in place. Solder the new diode to the same points on the circuit board where the original diode was soldered. Make sure that the diode is oriented correctly. The band on the diode should be facing the same way as the band on the original diode.
- Close the battery compartment. Once you've soldered the new diode in place, you can close the battery compartment and install the battery cover.
Testing Your Luna Pro
Once you've completed the update, you can test your Luna Pro with a modern 1.5 volt button battery. If the meter is working properly, the needle will move when you point it at a light source.
If the meter doesn't work, double-check your soldering connections. Make sure that the diode is oriented correctly and that the solder joints are strong. If you're still having problems, you may need to consult a qualified electronics technician.
Conclusion
By replacing the original diode with a new one, you can update your Gossen Luna Pro to function with modern batteries. This simple update will allow you to continue using your Luna Pro for many years to come.