Does battery pack changes exposure of Minox ?

I am thinking of using battery pack to replace PX27 in my C,

Since the battery pack is 6v instead of 5.6v, there is a change in

voltage of nearly 10%, does the expsoure time changes by 10% ?

Linda, I have not notice any change of exposure in my C when I use the battery replacemet pack instead of PX27 mercury battery.

in auto mode (A). I once compare the meter of two ECs, one with PX27, one with power pack; I stacked two EC together

and scanned them across window and check the red LED light in the window, when two cameras

scanned from dark to bright, the two red lights turned on at the same time, when they scanned from bright to darkness, the two lights turned on

at the same time. This indicates that exposure meter react to light or darkness exactly the

same regardless of 5.6V battery or 6v battery; otherwise the two lights should turn on or off at different time.

Linda, I am the guy who may have been responsible for the Minox

battery pack being developed. In the early 1990's when the

discontinuation of Mercury batteries was announced, I looked at my

collection and realized I would soon have a lot of very expensive

things that no longer worked. The PX-27 is very unique, and nobody

was going to make replacements just for C, EC and LX Minoxes, the

only things that use them as far I as I could find. I began

researching batteries extensively, buying all sorts of battery data

and testing equipment at Radio Shack, while I still had fresh PX-27s

to compare to. The main problem was the voltage. A PX 27 is,

internally, 4 stacked mercury button cells of 1.4 volts each. This

gives the 5.6 volt figure in the PX-27. Now, here is the problem.

Mercury batteries have a flat discharge curve. That is, voltage

discharge is almost constant until the battery goes dead suddenly.

This is unlike alkalines, which start higher than posted voltage, and

decrease gradually until dead. This is NO GOOD for a light meter: the

meter will not give consistant performance as the voltage gradually

changes. Silver oxide button batteries have a flat discharge curve

similar to mercuries, but they were all 1.5 volts. Too high, as I

reasoned that 4 of these would be 6 volts, as you did. Then, fiddling

around one day, I took 4 S-76 silver buttons I use in my 35mm cameras

and stacked them, and put a volt meter on the stack. VIOLA! The stack

read not 6 volts, as expected, but 5.6 volts!! (Some brand new fresh

S-76s might go to 5.7v. No big deal.) I reasoned that the metal

casings, when stacked in four cells, was causing a voltage drop due

to resistance of the metal casings themselves. I tried four S-76

buttons in one of my LX cameras. They fit, but barely, and only if I

put two end ones in first and squeezed the middle ones in next. Very

tight, but the LX worked perfectly. I compared to other LX's. No

discernable difference in exposure at identical subjects in the same

light. I was very concerned as to fit, as the 4 S-76s would only fit

in the LX, they wouldn't fit in C models at all, and the set was

clearly smashing the battery contacts flat in the LX. A search in

the Radio Shack battery manual revealed that the 386 silver button

had the same performance, discharge curves and discharge rates as the

S-76. Its main difference being less storage capacity, as it was

thinner, so it would not last as long. (Not a factor in a power-

stingy little Minox!) I bought four 386 buttons. Stacked, they too

tested 5.6 volts. Problem was, they now weren't thick enough to fit

across the battery chamber when stacked. I tried a metal spacer.

Bingo. This did it. I phoned Minox Labs the next day. We had been

discussing this and the lady at Minox confessed the factory didn't

have an answer yet and was very worried about the situation. I told

her of my experiments and what batteries I tried. I suggested that

four 386's and a spacer would work perfectly. She wrote it all down

and faxed it to the Minox factory in Germany to test out further.

About a year or so later, the Minox Battery Pack was introduced. It

is basically a metal spacer and a plastic sleeve to hold the four 386

buttons together. As far as anybody can tell, the battery packs

function identically. On a similar note, I have found that a single

1.5v silver oxide S-76 will power the Minox BL's meter very well,

with no difference in meter performance from the last mercury PX675

buttons I had. (External dimensions of the PX675 and S-76 are the

same.) The BL does not seem to notice the difference between 1.4v and

1.5v, at least to any degree that would make an observable change. I

recommend using these in BLs and not the alkaline PX675A substitute

that Minox Labs has been selling. That one will not deliver a flat

constant voltage discharge curve necessary for consistent metering.

Go ahead and use that pack in your C. I have them in my C models and

my LX's and they are all functioning perfectly, and identically to

the PX-27s. Don Thayer, owner of Minox Labs (whose father was the

person who imported the original Minoxes to the the USA in its

infancy) also told me there are no reports of any C, EC or LX not

functioning identically with the Packs as with PX-27s.

Mike

I have a question to Michael regarding this. Did you just push four silver oxide batteries in or did you use an adapter of sorts. My e mail is LCShainock@att.net

I have a question to Michael regarding this. Did you just push four silver oxide batteries in or did you use an adapter of sorts (I am talking about putting these into a Minox 35 PL). My e mail is LCShainock@att.net

I have a question to Michael regarding this. Did you just push four silver oxide batteries in or did you use an adapter of sorts (I am talking about putting these into a Minox 35 PL). Thanks for your help anyone.My e mail is LCShainock@att.net.

Larry,

you should rather not replace PX27 with 4 button cells in the minox 35. As Martin Tai has pointed out in another thread, batteries seem to have different internal resistances. The only replacement recommended by Minox for the 35 models is two CR 1/3 N Lithium batteries (by risk of shutter damage unless these are used). This can be accomplished by the Minox adapter which is (lemme think, Euro is stronger at the moment...) about 25 US$ in Germany. Therefore, I use a different method! I opened an empty Varta V27PX and found a hard paper tube filled with four MR 43 mercury cells plus several metal plates as spacers, the latter of which I discarded (mercury cells into battery waste, of course). The thing I needed was the hard paper tube. Two CR 1/3 N fit in perfectly; I put the whole thing into the battery tube of my 35 GL and closed it with just the normal screw top. Everything works fine - but as Linda had asked in the original question, in the 35 exposure changes by 10% towards underexposure, as slightly faster shutter speeds are measured. For negative films, this should not matter much. When buying films, you can choose "forgiving" ones; as I like b/w I prefer using the Ilford XP2 super (C41), but it should also be o.k. to use Classic Pan 400 (or Kodak Tri-X 400 for the professionals among us).

 

Jesko Matthes

Hello Jesko,

 

Hope you will read this message as it's been a long time since your last answer.

I am looking for a way to open my V27PX but can't really understand how to do it and if the hard paper tube your talking about is the outer shell or something inside.

yannick, the hard paper tube is in the inside, you need to ply off the metal outer shell to get to the hard paper tube.

Thanks Martin, I managed to do that and know I just need two CR 1/3N to make it work.

Do you know by chance if it would work with 4 357 buttons?

386, not 357