e_asphyx
Member
To use a battery with different voltage on Minolta Hi-Matic 7/7s and probably some other Minolta cameras like SR-T you need to recalibrate the meter. No diodes, black paint and other modifications are required. Here is the procedure I've came to.
The meter has two adjustment resistors. Be careful with them because they are headless and you can't use a screwdriver. You need a small plastic tool to push the level left or right. Right resistor (Radj2) controls circuit gain. Left one (Radj1) changes an offset. You can't tweak them individually since they're connected into a network. First after installing a new battery check the offset using a constant light source like a smartphone screen placed against the sensor and a reference light meter. By changing an offset make the camera meter display the same value as your reference meter. You can adjust the source brightness to get a round values on both meters. Then by changing ASA setting which changes a sensor aperture check the gain. Make a one stop change in either direction. If the camera's meter reading changes more than one stop reduce gain slightly or increase if it changes less. You must do it blindly as numbers won't say much at this point. Then return ASA selector to its original position and readjust an offset to get your reference EV again. Repeat as many times as needed.
The meter has two adjustment resistors. Be careful with them because they are headless and you can't use a screwdriver. You need a small plastic tool to push the level left or right. Right resistor (Radj2) controls circuit gain. Left one (Radj1) changes an offset. You can't tweak them individually since they're connected into a network. First after installing a new battery check the offset using a constant light source like a smartphone screen placed against the sensor and a reference light meter. By changing an offset make the camera meter display the same value as your reference meter. You can adjust the source brightness to get a round values on both meters. Then by changing ASA setting which changes a sensor aperture check the gain. Make a one stop change in either direction. If the camera's meter reading changes more than one stop reduce gain slightly or increase if it changes less. You must do it blindly as numbers won't say much at this point. Then return ASA selector to its original position and readjust an offset to get your reference EV again. Repeat as many times as needed.
