Mallory battery replacements

A friend gave me a couple nice old reflective light meters--one's a

Gossen Super Pilot SBC and the other's a Sedic P-120. Back in the

day, both meters apparently took a 1.35 v Mallory PX 13 or PX 625.

Anybody have an idea of a modern equivalent for these batteries?

 

Thanks much,

 

Steve

Zinc/air hearing aid batteries such as #675.

Or buy a battery adaptor: battery.adaptor@wanadoo.nl

Consider a Kodak (Germany) LR9 alkaline 1.5v cell. I have one right here, in its unopened packing.

 

The battery itself has 'LR9' stamped on it but the front of the package says '625A'; the rear, 'KA625'.

 

Catalog number is 527 8791. Mine has a Best Before date of (Jan.) 2008.

Steve, 1950s to 1970s electronic units regarding photography, whatever they were (external lightmeters, integrated lightmeters) that worked with one (or several in a battery pack) now banned mercury 1.35V battery generally known as 625PX or PX13 will NOT (I repeat... NOT, NOT, NOT :)) work properly with the 1.5V 25PX alcaline batteries although they are of the same shape.

 

They would "work", in a certain way. But you'd best let them in the cupboard, you'll be lighter in the field.

 

So you are left with two solutions :

 

1/having the internal potentiometer professionnaly adjusted to the 1.5V voltage instead of the original 1.35V (or 3V instead of the original 2.70V if two batteries are needed etc) but be aware that beyond the price you will be asked to pay for, using an alcaline battery where a mercury battery was needed isn't the best choice because of the non linear voltage response in time of the alcaline batteries (many good things have been written regarding that matter ; to sum-up, as soon as you fit the battery in the device, its voltage is not 1.5V any longer and continuously decreases until it's 0, so after a short period what the meter will indicate won't be accurate because the voltage output of the battery will promptly get down and finally be around 0.9V)...

 

2/buying or making yourself one (or several) MR-9 adapter that is an empty shell that has the shape of the 625PX and a clever built-in circuitry and is designed to be used with one (or several) 76PX 1.5V silver batteries. Once the small 76PX silver battery fitted in that thing, it transforms into something that delivers a constant (thanks to the silver battery) 1.35V voltage and has the proper shape.

 

Check on the Internet with a good search engine with these keywords : "MR-9 adapter", "Chottky diode", you will gather interesting info.

 

Ha, yes indeed, there is a third solution that consists of buying some not really cheap 1.3V zinc-air batteries that will not last more than one month once uncapped, but I wouldn't advice this unless you'd want to promptly get a damaged and corroded battery compartment...

 

:)=

amen to what has been posted. My own experoence with hearing aid zinc-air batteries ( in fairly humid pa) has been a life of several months in an old slr. But the "new" cells still with the tape on them were dead after less than a year. so back to the pharmacy dept for a new 6 pack.

I don't know why the silver cell is not suggested with an asa adjustment to compensate for the higher ( 1.6 as opposed to 1.35-1.4 ) voltage.

the silver cell has a flat discharge like the banned mercury cell.

a few old cameras ( pentax?) have a bridge-type circuit and can use an alkaline or mercury cell. the gradual voltage drop does not radically affect accuracy of the meter. many are fooled as color print film is tolerant of poor exposure and if they were using slide film it would be obvious. the shottky diode in series with a silver cell is supposed to work well. that type of diode has the lowest drop of any semi-conductor and " adjusts" the 1.6v cell to close to the perfect 1.35-1.4v.

The problem with that simple ASA adjustment as a compensation for the higher voltage is with the non linearity of the response of the CdS cell to light if the power voltage is not the good one, as there are two potentiometers, one for the low light range, the other one for the bright light range. At least it's like this in a Rollei 35.

 

The CdS cell is in series with an amplifier that is powered by the battery. So, in low light situations, using a 1.5V power source will lead to a 1 up to 1 1/2 IL error ; in very bright light situations, the error can reach 3 up to 4 IL with certain lightmeters.

 

So, the ASA dial trick might work... if you have a light chart to adjust the ASA dial accordingly to the light situation.

 

In other words : it works, if you have another lightmeter to help you to adjust the first in which you have fitted 1.5V battery(ies) instead of 1.35V battery(ies)... :-)

 

A kind of nice story... the lightmeter that is used to adjust the settings of the other lightmeter that is used to adjust the settings of the other lightmeter that is used to adjust the settings of the other lightmeter that is used to adjust the settings of the other lightmeter that is used to adjust the settings of the other lightmeter... :) hey, whatzitt dat dere ? Give me my camera back !

Heh. Okay.

 

Thanks, everyone. Luckily, my Canon has a nice spotmeter in it. I was just thinking of something to go along with my old Leica (and it has a MR lightmeter which is probably as good as these puppies). The Gossen just had an incident dome, and I thought it might be nice to have an incident meter now and again. For now, I guess these go on the shelf along with the other antiques.

 

Steve

E-mail: battery.adaptor@wanadoo.nl - I bought 2 PX625 battery adaptors off this fellow. He even gives you a 5 year warranty. It makes things very easy---no screwing around and bang on exposure.