Canon FTbn voltage conversion or adapter

[punkzter]

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

 

[sevo]

The conversion should do exactly the same thing as the adapter - namely, insert a drop diode or two into the circuit.

 

[Alfonso B]

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.

 

[Robert Lai]

I have a converted FTb, and it works just fine.

 

[Steve Bellayr]

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.)

 

[punkzter]

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?

 

[sevo]

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.

 

[punkzter]

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.

 

[Ranchu]

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

 

[AZPhotog]

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.)

 

[punkzter]

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.

 

[Ranchu]

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?

 

[Roger Hicks]

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.

 

[punkzter]

I purchased the Kanto brand...it seems nice

 

[Robert Lai]

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.

 

[Roger Hicks]

Thanks punkzter and Robert. Any other suggestions? If not I'll go for the Thai one.

Cheers,

R.

 

[Steve M.]

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.

 

[Roger Hicks]

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,

 

[Alfonso B]

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.

 

[Robert Lai]

Buy Pratedthai

Buy Pratedthai

For the record, we went through a long thread about these voltage adapters here:
http://rangefinderforum.com/forums/showthread.php?t=143181&highlight=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.