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Nikon Photomic FTN Meter Modification for Modern Batteries
The Nikon Photomic FTN is a classic light meter that was popular in the 1960s and 1970s. It’s a reliable and accurate meter, but it has one major drawback: it uses mercury batteries, which are no longer readily available. This tutorial will guide you through modifying your Nikon Photomic FTN to accept modern batteries, extending its life and ensuring its continued use.
Why Modify?
Mercury batteries, while providing a stable voltage, are no longer manufactured due to their environmental impact. Using a modern battery requires a modification to compensate for the voltage difference, ensuring the meter functions correctly.
Materials
- Nikon Photomic FTN light meter
- Small Phillips screwdriver
- Voltage dropping diode (1N4001 or similar)
- Soldering iron and solder
- Heat shrink tubing
- Optional: Multimeter
Procedure
- Disassemble the Meter Prism
Carefully remove the prism assembly from the meter by unscrewing the four screws holding it in place. Be gentle as the prism is delicate and could be damaged.
- Locate the Battery Contacts
Inside the prism assembly, you’ll find the battery contacts. Identify the positive and negative terminals. The positive terminal will usually be marked with a ‘+’.
- Install the Diode
Solder the voltage dropping diode to the battery contacts. The diode should be connected in series with the positive terminal. Make sure the diode is oriented correctly, with the band on the diode facing the negative terminal.
- Test the Circuit
If you have a multimeter, test the circuit to ensure the diode is working correctly. Connect the multimeter’s probes to the battery terminals and verify that the diode drops the voltage from the battery to the desired level.
- Reassemble the Meter
Once the diode is installed, carefully reassemble the prism assembly, ensuring all screws are securely tightened.
- Test the Meter
Insert new batteries (silver oxide or lithium) and test the meter. It should function normally, and the needle should deflect appropriately when exposed to light.
Important Notes
- This modification is for experienced individuals comfortable with basic electronics.
- Always handle the meter and its components with care to avoid damage.
- Use a suitable soldering iron and solder to ensure a secure connection.
- If you’re unsure about any aspect of the modification, consult a qualified technician.
This modification allows you to extend the life of your Nikon Photomic FTN light meter and continue using it with modern batteries. Remember to handle the meter with care during the modification process, and always test the circuit before reassembling the meter.