PX625
Before mercury batteries were banned, many cameras were designed to use them. Mercury batteries produced a contant and reliable voltage, so many cameras were built without any voltage regulation in the metering circuitry. Now that we can only get alkaline batteries, the classic cameras many of us love give erratic exposures and meter readings.
Rick Oleson offers some suggestions based on ideas from Leon Schoenfeld to make your classic cameras give acceptable meter readings using modern alkaline batteries.