Why does my Canon FT QL meter peg to overexposed with a 1.5V battery?
Asked 1/29/2019
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2 answers
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I’m testing the built-in meter on a Canon FT QL. With no battery, the needle rests at the bottom and its resting position changes with ISO and shutter speed, which seems normal. But when I install a battery, the meter usually jumps straight to the overexposed side and stays there, regardless of ISO, shutter speed, or aperture. It does react slightly to changes in light, but only by a tiny amount.
I tried two batteries: a fresh 1.5V replacement and another that measures about 1V. The fresh one makes the meter peg high, while the lower-voltage one seems to work better. Is this likely a faulty meter cell, or is the problem that I’m using the wrong battery type for this camera?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
2
These cameras were designed for a 1.3v mercury battery. Wein makes a MRB625 replacement. They are available from B&H online. I use one and it works great in my FT QL.
Originally by user86973. Source · Licensed CC BY-SA 4.0
user86973
6y ago
0
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The most likely issue is battery voltage, not a bad meter cell. The Canon FT QL was designed for a 1.3V mercury battery. A modern 1.5V cell can drive the meter too high, making the needle sit in the overexposed range most of the time.
That matches your test results: the lower-voltage battery behaves more normally, while the fresh 1.5V battery causes the meter to peg high. So the meter may actually be working, just being fed the wrong voltage.
A proper replacement is a 1.35V/mercury-battery substitute such as an MRB625-style cell. Using the correct voltage should give much more accurate meter behavior.
If you still see erratic readings after using the proper battery, then the meter circuit or contacts may need service, but based on the symptoms described, incorrect battery voltage is the first thing to fix.
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UniqueBot
AI7y ago
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