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Canon Rangefinders - Peter Dechert and Peter Kitchingman Peter Dechert is best known for his Canon Rangefinder, Canon SLR, and Olympus Pen books, the latter two long out-of-print. He was a monthly columnist for many years for SHUTTERBUG magazine, and has contributed to many others. Most recently he has written about the pre-WW2 Zeiss 35mm cameras, but his interests in camera equipment and optics are many and varied. As a pro protographer and honorary life member of ASMP, Peter is also expert in using the gear! Peter Kitchingman - author of Canon Rangefinder Lens book Peter Kitchingman's 'Canon M39 Rangefinder Lenses 1939-71' book is the definitive source on these very interesting optics. His interests also go to the entire Canon Rangefinder system and beyond.

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MR-9 battery adapter issue
Old 08-28-2017   #1
folksnake
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MR-9 battery adapter issue

Hi All-
I ordered a battery adapter for my Canonet G-III 17 from CRIS and just got it. Excited, I tested the battery itself (new 386) and it was at 1.584V. Ok, it's fresh!

Inserted it in the adapter and the voltage now read 1.555V. This is one of those adapters that has the built-in diode to drop the voltage to 1.35V.

Is this normal? The instructions say "386 battery voltage is reduced to 1.35 volts when the camera or meter is turned on."

Does that make sense that the adapter would need a load to drop the voltage correctly? What about the original mercucry batteries--were they 1.555V also, until the meter was turned on? Odd.

Admit I'm a little confused, and a little miffed, in that the package cost me nearly $50.

Thanks!
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Old 08-28-2017   #2
CMur12
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As I recall from previous discussions here, when there is a load on the battery/adapter, it measures 1.35v. Without the load, measuring it with a modern digital meter will show 1.55v. I have an older analog volt-ohm meter, and it shows the desired 1.35v.

These adapters have worked very well for me and I would expect yours to function as intended.

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Old 08-28-2017   #3
AZPhotog
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What CMur12 said. Absolutely correct.

These adapters are very well made and reliable. You can be assured that when the camera circuitry loads it, the adapter will provide the 1.35 volt output.
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Last edited by AZPhotog : 08-28-2017 at 21:43. Reason: additional info
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Old 08-29-2017   #4
wolves3012
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Quote:
Originally Posted by folksnake View Post
Does that make sense that the adapter would need a load to drop the voltage correctly?
Yes, it does make perfect sense, from an electrical viewpoint. A modern DVM draws very little current so it doesn't present a load to the adapter. No current flow = no voltage dropped across the diode, so the meter just reads the full battery voltage (almost).
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Old 08-29-2017   #5
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Excellent! Thanks so much for the reassurance. I was hoping that nothing was amiss, but couldn't be sure.

Now to figure out why the Battery Check indicator won't light with the adapter, but does so with the old battery that was in the camera when I purchased it...

Thanks. Invaluable to hear experienced responses!
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Old 08-29-2017   #6
sevo
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Originally Posted by folksnake View Post
Now to figure out why the Battery Check indicator won't light with the adapter, but does so with the old battery that was in the camera when I purchased it...
Mercury and silver oxide cells are voltage sources, so they show their nominal voltage on low loads (e.g. digital meters) even way past their useful work life, while they are decreasingly capable of maintaining any useful current over time as they discharge. Simply measuring voltage accordingly won't do, and even measuring voltage under regular work load often does not tell you whether the battery will fail another minute on. To get a more reliable assessment of the cell status, battery indicators often work by putting a unusually high load on the battery - where a stale battery will black out while a good battery can handle that.

These test loads may be too much for the adapter, as drop diodes have maximum as well as minimum current limits.
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Old 08-29-2017   #7
Mark Wood
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The Canonet battery indicator light is a known issue with these adapters, so nothing to worry about. It's mentioned in some of the sales information here:

http://www.smallbattery.company.org....r9_adapter.htm
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Old 08-29-2017   #8
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Thanks to everyone who has replied. You're all spot on, of course. I'm good now

I also got a response from CRIS and they sent out a pdf explaining how to properly test the adapter (10Kohm resistor in the testing circuit). If the voltage reduction happened without a load, it would constantly drain the battery, even when stored ans turned off. Makes sense.

Thanks again for straightening this out for me!
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