MR-9 adapter voltage question

[BrianShaw]

Difference between SR43 and SR44 is in height only, there is no difference otherwise as far as what adpater does to its voltage. But the height difference is why on some cameras the cover will not screw all the way in (Leica M5 comes to mind, where SR44 makes it near impossible to get the threading even started).

According to the specs, there also appears to be a difference in discharge curve charachteristics between the two cells. In my experience, this diffference has been negligible effect, if anything.

 

[Bwbuff]

True, but unfortunately, my Konica cameras lack the bridge circuit and are reliant on a constant 1.35 volt source.

The OP, @Bwbuff, does not say what camera his MR-9 adapters will go in. We probably should have asked sooner, to verify he actually needs the voltage adjustment.

It is the Minolta SRT 200. I should have mentioned it earlier.

 

[chuckroast]

According to the specs, there also appears to be a difference in discharge curve charachteristics between the two cells. In my experience, this diffference has been negligible effect, if anything.

The difference between 1.35V and 1.5V is about 11%. While is does not necessarily follow that meters will thus be off only 11% (it depends on the design of the meter), my experience is that the significance of this difference is usually an overstated worry. Within the limits of the linearity of the meter at the ends of its measurement range, you can dial in a lower EI to overcome the tendency of a meter to underexpose when running with the higher voltage.

The greater concern is that the only batteries made today that will physically fit in the old PX625 form factor are alkaline. Alkaline batteries have a well known problem of gradually losing voltage over time and this gradually introducing measurement error with meters. The better solution here is to use silver oxide or lithium batteries, none of which are made in that form factor any longer. The silver oxide and lithium batteries maintain their voltage until end of life and then fail very rapidly.

So, if you have meter that still expects a 1.35V battery, you need a voltage dropping device like a true MR-9 with a silver oxide battery installed.

If you've had the meter re-calibrated for 1.5V, you need a physical adapter without a voltage dropping diode just to be able to use the smaller SR43 or SR44 batteries. As has been pointed out upthread, these can sometimes stand "proud" of the battery compartment and make threading in the cover difficult. Some people have reported good results by using o-rings to hold the smaller batteries in place in the larger 625 battery compartments.

I was fortunate to squirrel away some S625 batteries when they were still being made. I use this with my re-calibrated M5. When they are gone, I will have find an SR43/44 solution that works.

 

[BrianShaw]

Im not sure what you are reacting to in that very educational post, @chuckroast

My point was simpler than that, the discharge curves between those 2 silver oxide batteries appear different. One is flatter than the other in the respective spec sheets.

 

[chuckroast]

Im not sure what you are reacting to in that very educational post, @chuckroast

My point was simpler than that, the discharge curves between those 2 silver oxide batteries appear different. One is flatter than the other in the respective spec sheets.

Sorry, I wasn't particularly responding to you but the general topic. I think we make much if these fine points when many of the older meters, especially, aren't accurate to within 11% in the first place

It was meant to be expository, not reactive ... d'oh ...

 

[Craig]

Before the sanctions on Russia, I was able to buy PX625 mercury batteries on ebay from Russia. They work perfectly in a Gossen Lunasix and an old Canon F1, but they wouldn't physically fit in a friends Leica M5. The M5 in particular seems to have a small battery compartment.

 

[BrianShaw]

Sorry, I wasn't particularly responding to you but the general topic. I think we make much if these fine points when many of the older meters, especially, aren't accurate to within 11% in the first place

It was meant to be expository, not reactive ... d'oh ...

Like.

Plus, this same topic seems to come up annually. It’s actually been discussed and rediscussed. Im always surprised when folks seem to indicate that decade old proven solutions might not work. New and alternative approaches are great, but…

 

[chuckroast]

Before the sanctions on Russia, I was able to buy PX625 mercury batteries on ebay from Russia. They work perfectly in a Gossen Lunasix and an old Canon F1, but they wouldn't physically fit in a friends Leica M5. The M5 in particular seems to have a small battery compartment.

Well, that's an issue, but the mercury content was the bigger problem. The no-longer-made S625 batteries were the perfect solution for M5s. You might try to o-ring + SR battery approach.

 

[chuckroast]

Like.

Plus, this same topic seems to come up annually. It’s actually been discussed and rediscussed. Im always surprised when folks seem to indicate that decade old proven solutions might not work. New and alternative approaches are great, but…

Maybe we need a sticky summarized response somewhere here on site to point out to folks. Or does that already exist, I wonder...

 

[wiltw]

The difference between 1.35V and 1.5V is about 11%. While is does not necessarily follow that meters will thus be off only 11% (it depends on the design of the meter), my experience is that the significance of this difference is usually an overstated worry. Within the limits of the linearity of the meter at the ends of its measurement range, you can dial in a lower EI to overcome the tendency of a meter to underexpose when running with the higher voltage.

The greater concern is that the only batteries made today that will physically fit in the old PX625 form factor are alkaline. Alkaline batteries have a well known problem of gradually losing voltage over time and this gradually introducing measurement error with meters. The better solution here is to use silver oxide or lithium batteries, none of which are made in that form factor any longer. The silver oxide and lithium batteries maintain their voltage until end of life and then fail very rapidly.

So, if you have meter that still expects a 1.35V battery, you need a voltage dropping device like a true MR-9 with a silver oxide battery installed.

If you've had the meter re-calibrated for 1.5V, you need a physical adapter without a voltage dropping diode just to be able to use the smaller SR43 or SR44 batteries. As has been pointed out upthread, these can sometimes stand "proud" of the battery compartment and make threading in the cover difficult. Some people have reported good results by using o-rings to hold the smaller batteries in place in the larger 625 battery compartments.

I was fortunate to squirrel away some S625 batteries when they were still being made. I use this with my re-calibrated M5. When they are gone, I will have find an SR43/44 solution that works.

Back when the mercuric oxide were announced to be taken off the market in the US (Europe did it sooner than USA) I still had new PX-13 in the drawer, and I tried inserting the alkaline chem button cell into my OM-1N for testing. I discovered that there was not a constant shift in magnitude of error introduced, the degree of error was greater dependent upon the light level being metered! So an ISO offset to 'correct' the error was not simply for 'new' vs 'somehwat used' alkaline Voltage decline it also had to be 'low' vs. 'bright' (and intermediate level dependency was not determined) light level as well. So I am well aware of the Olympus OM-1 high degree of dependence on the constant 1.35V output from mercuric oxide cell (or appropriate mod by a knowledgeable camera tech) That is what motivated me to buy the original MR-9 from the original source decades ago.

 

[koraks]

The difference between 1.35V and 1.5V is about 11%. While is does not necessarily follow that meters will thus be off only 11%

That's right, it doesn't. I've had cameras that were about 1 to 1.5 stops off with the higher voltage battery.

 

[benjiboy]

Is the MR-9 adapter only accept SR43 battery according to the description from the packaging ? I don't have any SR43 to test, I had tried the LR44 and SR44w without the adapter the voltage shows 1.56v and 1.59v. With the adapter , the voltage did not drop to 1.35v as expected, it shows 1.51v and 1.52v respectively. I tried both adapters , the results are the same . These are the Kanto camera MR-9 from Japan. Also I tried the Zinc air 1.35 V with/without the adapter, the voltage remains 1.35 volt.
Any idea why ? thank you.

I have 2 MR 9 adaptors one for each of my Canon F1 n's , I find that with the correct SR43 Silver Oxide batteries they reduced the voltage by 1 volt and work perfectly, however I don't expect that they will work correctly with batteries they were not designed for.

 

[Bwbuff]

I have 2 MR 9 adaptors one for each of my Canon F1 n's , I find that with the correct SR43 Silver Oxide batteries they reduced the voltage by 1 volt and work perfectly, however I don't expect that they will work correctly with batteries they were not designed for.

Thanks, I just ordered the SR43, when it arrives I will measure it again.

 

[runswithsizzers]

I find that with the correct SR43 Silver Oxide batteries they reduced the voltage by 1 volt and work perfectly,

When you say, "they reduced the voltage by 1 volt" -- can I ask about your measurement technique?

Isn't a reduction of 1 volt a lot more than expected with a MR-9 type adapter?

 

[qqphot]

When you say, "they reduced the voltage by 1 volt" -- can I ask about your measurement technique?

Isn't a reduction of 1 volt a lot more than expected with a MR-9 type adapter?

that would certainly be a surprising voltage drop from a schottky diode. The problem with these adapters is that the tiny current draw of most metering systems places the diode in the part of its curve where it's sort of like a diode but also sort of like a resistor. With higher current the fixed voltage drop dominates (it's decidedly nonlinear) and from nothing up to some small current it acts like a resistor, where voltage drop does depend on current. In either case the drop normally wouldn't exceed the 0.45v or whatever that the diode exhibits in the nonlinear region of its curve.

 

[benjiboy]

runswithsizzers:
When you say, "they reduced the voltage by 1 volt" -- can I ask about your measurement technique?
Isn't a reduction of 1 volt a lot more than expected with a MR-9 type adapter?
I tested the battery voltage alone with a digital multimeter, then put the battery in the adapter and tested it again using the same method.
The two Canon F1ns I use them in give correct exposure using a Kodak Grey Card,and a digital spot meter, and comparing the readings.