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Canon FTbn voltage conversion or adapter
Old 03-20-2017   #1
punkzter
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Canon FTbn voltage conversion or adapter

Hi,

I'm sending a Canon FTbn to Ken Oikawa for a CLA and anything else that it may need. I was curious if there was a general consensus on whether or not to get the voltage conversion. I do happen to own a Kanto MR-9 adapter (purchased on ebay). But I figured that the conversion may make life easier.

But then I read a few threads that stated that the meter did not perform as well after the conversion and that the adapter was the way to go.

So I'm confused. The camera is on it's way to Ken, and I do plan on asking his opinion as well. But I thought I'd reach out for thoughts here.

Thanks!

~Brad
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Old 03-20-2017   #2
sevo
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The conversion should do exactly the same thing as the adapter - namely, insert a drop diode or two into the circuit.
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Old 03-20-2017   #3
Alfonso B
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Quote:
Originally Posted by sevo View Post
The conversion should do exactly the same thing as the adapter - namely, insert a drop diode or two into the circuit.
This. And losing 50% of the cell diameter drops 3/4 of battery capacity.
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Old 03-20-2017   #4
Robert Lai
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I have a converted FTb, and it works just fine.
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Old 03-20-2017   #5
Steve Bellayr
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I use a converter. I was advised by the camera repairman that I could use a 675 hearing aid battery. If I wanted to center the battery use 20 gauge automotive wire and form a circle in the battery compartment to keep the battery from moving. (The battery is not small enough to move away from the poles. The wire will make you feel better.)
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Old 03-21-2017   #6
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I took a reading on the 1.5v Duracell 301/386 battery that I purchased, and the voltage starts off at 1.593

Using the converter (Kanto MR-9) that I purchased, the voltage drops to 1.469

Is that because the battery is new?
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Old 03-21-2017   #7
sevo
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Quote:
Originally Posted by punkzter View Post
I took a reading on the 1.5v Duracell 301/386 battery that I purchased, and the voltage starts off at 1.593

Using the converter (Kanto MR-9) that I purchased, the voltage drops to 1.469

Is that because the battery is new?
No, that is because the load digital voltmeters impose on the diode is way too low - good ones have a resistance deep in the MOhm range. Put some resistor (something between 5-50kOhm will give a reasonable representation of a CdS/pointer instrument camera circuit at work) in parallel, and the voltage should drop to something reasonably close to 1.35V.
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Old 03-21-2017   #8
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Okay, thanks.

So, from the above discussion, I guess it doesn't make any difference if I do the conversion or just use the adapter.
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Old 03-21-2017   #9
Ranchu
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Here is a good amount of info. You'll want to use silver oxide batteries rather than alkaline...http://www.butkus.org/chinon/batt-adapt-us.pdf
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Old 03-21-2017   #10
AZPhotog
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Go with the MR-9 Schottky diode adapter and the Duracell 301/386.
It is the best way by far, and that combination provides for a very long-lasting metering setup. (Long battery life as opposed to a smaller battery.)
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Old 03-21-2017   #11
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So that I understand, if I went with the internal conversion, I could still use the 301/386 battery, but I would have wasted the money on the adapter.

I might also need to purchase another mr-9 adapter, that doesn't do the voltage conversion.
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Old 03-21-2017   #12
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Yes. That's the problem, you still have to make a spacer of some kind if you have the camera modified, because silver oxide batteries don't come in the larger size. There are some aluminum non diode adapters from japan on ebay that are good. 12 bucks for two I think?
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Old 03-21-2017   #13
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Quote:
Originally Posted by AZPhotog View Post
Go with the MR-9 Schottky diode adapter and the Duracell 301/386.
It is the best way by far, and that combination provides for a very long-lasting metering setup. (Long battery life as opposed to a smaller battery.)
Which one? The Thai version? (I'm looking to buy one).

Cheers,

R.
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Old 03-21-2017   #14
punkzter
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I purchased the Kanto brand...it seems nice
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Old 03-21-2017   #15
Robert Lai
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The Thai one is great. All gold plated for the best conduction.
The MR-9 is steel or chromed brass, and didn't work as reliably in my Canon 7s. I think it was a conductivity issue. When I gently pulled the battery springs on the cap up to increase their tension, it worked much better. However, it is flawless with the Thai adapter.
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Old 03-21-2017   #16
Roger Hicks
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Thanks punkzter and Robert. Any other suggestions? If not I'll go for the Thai one.

Cheers,

R.
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Old 03-21-2017   #17
Steve M.
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Whether or not you put a 1.35V or 1.5V battery in it makes little difference. It is not going to need any more than an ISO tweak w/ either to perform just fine. All of mine worked perfectly w/ either battery.
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Old 03-21-2017   #18
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Quote:
Originally Posted by Steve M. View Post
Whether or not you put a 1.35V or 1.5V battery in it makes little difference. It is not going to need any more than an ISO tweak w/ either to perform just fine. All of mine worked perfectly w/ either battery.
Dear Steve,

I've heard this from several people too. The important thing to avoid, as I understand it, is alkaline cells because of their very non-linear discharge curve. Silver or lithium are preferred, and even then, some have suggested that they can affect linearity of response even at nominal voltage. Any advice on either? From you or others?

In particular, I'm thinking of MR and MR-4 meters on a Leica and a Gossen Lunasix.

Cheers.

R,
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Old 03-21-2017   #19
Alfonso B
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The linearity of metering inaccurance might vary by camera. There are circuits with passive components and semiconductor-based meters. My OM has the latter, no calibration possibility whatsoever, and started metering correctly when I added a 1n4148 diode (couldn't find my schottky stash). My CL has a ****load of trimmer pots, you can even adjust the linearity. CL's error was nonlinear so no ISO compensation could fix it.
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Buy Pratedthai
Old 03-21-2017   #20
Robert Lai
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Buy Pratedthai

For the record, we went through a long thread about these voltage adapters here:
http://rangefinderforum.com/forums/s...ght=pratedthai

For the Leica MR-4 meter, I have a controversy. Don Goldberg feels that the MR-4 can be adjusted to work with the 1.5V silver cells, and makes the adjustment.

Gus Lazzari firmly believes that the linearity may be affected, so he suggests that you use the Pratedthai adapter on his serviced MR-4s.

I've got several MR-4, serviced by both Don and Gus. So far they all seem accurate.
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Old 03-21-2017   #21
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Quote:
Originally Posted by Robert Lai View Post
For the record, we went through a long thread about these voltage adapters here:
http://rangefinderforum.com/forums/s...ght=pratedthai

For the Leica MR-4 meter, I have a controversy. Don Goldberg feels that the MR-4 can be adjusted to work with the 1.5V silver cells, and makes the adjustment.

Gus Lazzari firmly believes that the linearity may be affected, so he suggests that you use the Pratedthai adapter on his serviced MR-4s.

I've got several MR-4, serviced by both Don and Gus. So far they all seem accurate.
Dear Robert,

Thanks again. Is this adjustment internal (and if so where) or can you just do it on the ASA scale?

Cheers,

R.
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Old 03-21-2017   #22
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I use the 675 hearing aid battery in my F-1, and it seems to work just fine.
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Old 03-21-2017   #23
Robert Lai
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Dear Roger,
The adjustment to accommodate 1.5V is done internally by Don. I'm not privy to what he actually does to make the adjustment. You set the normal ASA as per your film speed.

The test I did for the pratedthai comparison was with an MR-4 that had been serviced by Gus, and it required the 1.35V power source.
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Old 03-21-2017   #24
Steve Bellayr
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Look at this way: If you do the conversion you will have fixed the problem on one camera. If you go with the adapter you can use it on additional cameras.
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Old 03-22-2017   #25
sevo
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Quote:
Originally Posted by Steve Bellayr View Post
Look at this way: If you do the conversion you will have fixed the problem on one camera. If you go with the adapter you can use it on additional cameras.
... or you will always have to wonder where you last put the adapter!
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Old 03-22-2017   #26
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If I decided to do the conversion, what is the recommended battery? The new mr9 batteries are alkaline.

Would the recommended path be a 386 with a non-voltage altering adapter? Is there a favorite adapter of this type?
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Old 03-22-2017   #27
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If you want just a battery holder to fit the battery chamber, then nobbysparrow in Japan (that's his ebay name) sells two of them for $12. It won't convert the battery voltage at all, just holds the battery. That's what I use for cameras that have had the voltage adjusted to take 1.5V.

Even in them, I use silver oxide cells, as they have a flat discharge curve. Alkaline cells will continue to run down in voltage as they drain, so who knows what voltage they are putting out today?
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Old 03-22-2017   #28
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Quote:
Originally Posted by AZPhotog View Post
Go with the MR-9 Schottky diode adapter and the Duracell 301/386.
It is the best way by far, and that combination provides for a very long-lasting metering setup. (Long battery life as opposed to a smaller battery.)
This is what I use in my old Canon (F-1n, TX) cameras, and it works great. The silver oxide 301/386 batteries have a "discharge/per life" characteristic curve similar to the mercury oxide batteries that these cameras were designed for. Unlike alkaline batteries.

Best,
-Tim
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Old 03-22-2017   #29
Roger Hicks
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Quote:
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Dear Roger,
The adjustment to accommodate 1.5V is done internally by Don. I'm not privy to what he actually does to make the adjustment. You set the normal ASA as per your film speed.

The test I did for the pratedthai comparison was with an MR-4 that had been serviced by Gus, and it required the 1.35V power source.
Dear Robert,

Thanks.

Cheers,

R.
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