Zinc Air batteries and FTb

I'm in the process of buying a used FTb/ FTb N camera. Its kinda

cool to go right back to basic photography with match needle

metering. What I'm wondering is about the PX 625 battery. Most out

there are alkaline 1.5 volt versions. I know a store that brings in

the Wien Zinc Air battery with the correct 1.35 voltage. I have read

the life expectancy of these types of batteries is very low. One guy

said his lasted between a month to two months- at that point the

meter was off because the battery was low. Has anyone had any

problems using these batteries and them lasting? They're not cheap.

My other option is to just put the alkaline battery in it, send it

to a shop to be recalibrated in the meter, and go from there. But

that mean dollars as well. Any help on this issue would be great. I

live in Canada, but I don't think they have the mercury batteries

here anymore either.

I still see the correct mercury 1.35v on ebay usa out of GB and China. The stability and long life is worth the $8 bill. You may still get them in canada, I'd try for the proper battery first.

One choice is to use a 675 zinc-air hearing aid battery and to put a small rubber O ring around it. The 675 has 1.4 volts and I find that this inflates your reading by one stop. If you are shooting 200 speed film you would set the meter at 100. These won't last any longer than the Wein calls but are much cheaper. The best solution is to buy an MR-9 adapter from C.R.I.S. along with a supply of silver oxide batteries. The adapter changes the volatge from 1.5 to 1.35. It will work with a standard MS-76 battery but the battery cover will stick out a little more than usual. The slightly thinner silver oxide batteries from C.R.I.S. will allow the cover to screw in all the way and are inexpensive. A silver oxide battery in an MR-9 adapter can last a year if you remember to turn off the meter when you are not using the camera.

 

I did not have good experience getting the meters of other makes recalibrated to 1.5 volts. I find that doing this can change the sensitivity at the high or low end of the light level. I have used the MR-9 in an FTbN, an F-1 and a Minolta SRT-101 and it worked well in all three. You can find C.R.I.S. on the internet.

I prefer the generic 675 Zinc-Air batteries along with the Rubber O-ring mentioned in Jeff's post. I have used these with good results in a Canon TX, which is basically a slightly stripped-down FTb-n.

 

I actually have a one-page ap-note on using these 675 Zinc-Air cells with the rubber O-ring, which I'll send to anyone who e-mails me for it.

 

The generic 675 cells are electrically identical to the Wein cells, except that they cost under $1 a piece, so it's no big deal if they only last 6-8 weeks. The Wein cells are really just a 675 cell put in a metal sleeve taht makes it fit into a 625-size chamber. They claim that they also modify the anode to slightly drop the voltage from 1.4 to 1.35 V, but my tests show that the voltages are measurably the same (and, BTW, well within the tolerances of most meter circuits).

If anyone has any Canadian sources for the old Mercury batteries- let me know. What does the QL stand for that these cameras mention? The camera I'm looking at is the non N version.

QL, stands for quick loading

I use a wien cell in a QL17 (rangefinder) and it is still kicking after a couple of months. You can get them at Henrys - or go the drugsotre/gasket way. Apparently my QL17 has voltage compensating built in (photoetnography site claims this) - but I doubt the FTb does. I don't know wether this is to account for the reading being usually very close to my AE1.

FYI, the life expectency of the Wein cells, or generic Zinc-Air cells, is a function of the humidity of the climate you live in. In a dry climate like southern California or Arizona, they will only last 4-6 weeks, once activated by unsealing the anode. In a humid climate, they might last 4-6 months.

http://www.criscam.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=CCS&Category_Code=MBA

 

I found this address for an adapter MR-9 which uses a silver oxide 386 cell. This looks to be the best answer for this camera.

 

Anyone have any opinions on the FTb camera? I have an AE-1 already, but a second FD backup would be nice. And I started my photo hobby using a Pentax K-1000, so to me that is the same as a FTb.

An FTb, as long as it's in good shape, is a more featured camera than a K1000 - Most importantly, it provides depth of field preview, which is missing from the K-1000. But I'm of the opinion that the FTb is rather heavy and complex compared to a K-1000. It's also more rugged than an AE-1.

i like the idea of the silver - oxide but the cris uses a resistor drop.

which is not the best way nor the most accurate. possibly non-linear.

 

 

generic zinc-air cells ( hearing aid cells)

have 4 holes, wein have 2?

a speck of nail polish ot crazy glue on 2 holes will slow down the drying out process and lengthen the life of a hearing aid cell.

 

do NOT stock up, they can dry out eventually even with the tab still in place. save the tab and when you are not using the camera replace the tab.

 

I cannot see the 1/2 hour delay for the cell to " come up to full power" I am not sure if it is true.

anyway, they are cheap enough to replace when the meter droops.

 

I have heard the canonet 28 will work with an alkaline cell, don't know.

Hi Scott-

 

With any 25 to 30 year old camera of this type, the meter battery voltage may be the least of your worries. It only makes sense to worry about the last few hundredths of a volt when everything else is working within specs. The most common exposure problem with this type of camera (not limited to Canon of course) is that the shutter speeds will be off significantly and perhaps even capping at the highest speeds.

 

If the camera hasn't been serviced recently (or ever) this problem will need to be adressed first and at a higher cost than any of the battery voltage fixes. Also, the Ftb is really in that first generation of ttl metering circuits and the factory spec for accuracy will be at least +/- half a stop at best.

A #675 zinc-air cell will give spot-on voltage --- if your meter reads a stop off with one, your meter's a stop off, not the battery. they're the same thing that's in the Wein cell but they cost less than a dollar each.

 

My own FTb meter, however, reads off and happens to come up pretty close with a silver cell of the same size. Maybe somebody's done that on purpose, i haven't had the camera that long. I use Zinc-air cells in most of my older cameras though, the meters are right on with them and i get a little over 6 months per dollar in kentucky (I hear they don't last as long in drier climates).

 

Between the main page (my opinions) and the links at the bottom (other folks'), you can find information on just about all of your options here:

 

http://rick_oleson.tripod.com/index-111.html

 

.... but heck, who really needs a meter anyway? load 'er up and shoot some film.....

 

rick :)=

oopss... i just tried the rolleiclub.nl link on that page and their site has gone dead. that was a really in-depth look at the issue.

 

i think i may have printed the whole thing out and saved it somewhere; i may scan it and re-post it on my site. if anyone feels like this would be a good use of time and bandwidth, please email me and offer encouragement.

 

rick :)=

Walter, the Zinc-Air ramp-up delay is more like 1 to 2 minutes, rather than a half hour. And if you store the Zinc-Air cells in the fridge (or, since the original poster is Canadian - outdoors LOL!), they will effectively live forever prior to activation.

I have a pdf soft copy of the document Rick is referring to. I put it up here: http://home.comcast.net/~hgolds/Battery_Adapter.html

 

I'll leave it up for a week or so.

 

I did purchase one of the adpaters and find that it works well in my Rollei 35.

sonofagun.... i went to save a copy of that .pdf and found i already had saved one... thanks harris!

 

i have room for that on my site, i'll go ahead and put it up so the link will work again.

 

rick :)=

Hey there.... just my .02... I have the old FTB-QL and a first run F-1. There's another way to power the meter that's kept mine going.. There are 625 size silver oxide cells. They have the same discharge slope as the mercury, last about as long too, they're just a bit higher on the voltage. The cheap way around the difference in voltage is to slip the asa scale. Use the battery check to find out how much "over" the voltage is, slip the scale until you get the right battery check, and then slip the scale from the film speed. (It *really* is easier than it sounds.... :) Mine wind up being at ASA 25 when I'm shooting 64 film, ASA 80 when shooting 200 film, ASA 160 when shooting 400, etc. Just count the dots on the battery check and it's the same compensation all the way... You just have to do it once to find out how much your meter over-reads. Mine are both four "dots" on the ASA scale. It's cheap, it works, and it lasts, what else can I say??? oh, btw, don't do the alkaline, the voltage drop during the battery life looks like a hill, and the ftb doesn't have a voltage regulator.

 

--Dan

Jeff and Doug are on the money with the 675 hearing aid batteries and the O-ring. I did that with my FTb-N, and used an A-1 (GREAT METER) to compensate the film speed settings on the FTb. From ASA25 to ASA800, under controlled conditions, setting the FTb film speed one and two thirds (1 2/3ASA)slower than called for gave me meter readings identical to the A-1. Thus for 100ASA, set film speed indicator at ASA25 plus 1/3 of a stop, etc. Well, it works for me. By the way,you are going to love the quick-load feaure on that camera!).

Hi Dan:

 

I think you may find that the amount of error from the 1.5v silver cell is not the same in bright light as it is in low light, though the difference may be small enough that you can get a good workable compromise that way.

 

I didn't realize there were silver cells in the 625 size; I've only seen the alkalines....

 

:)=

Rich... Not a problem, I tested against the last mercury cell I had, and if memory serves, the readings were plus or minus 1/3 of a stop between bright outdoors and interior lighting, tho i haven't done major testing with slides. you can find them by googleing s625px. There's also an e*ay store selling them, look for "px625 silver" The best things about using them is that you don't have to worry about temperature affecting the output of a schottkey diode, and the capacity is about the same as the old mercury, so they should last about as long as those did... :)

 

--Dan

<p>You can use an SR44 which has a voltage of 1.5. You have to compensate by a -1stop on your ISO because the higher voltage tends to underexpose readings. The amount of compensation may vary from one unit to another so you have to do some trial and error.<br>

Silver oxides are good because they last and they maintain a steady voltage thoughout their batery life. <br>

You just need to find an insulated wire and shape it around your SR44. Now put that wire in the chamber. It should hold the battery and prevent it from moving around it. It's a very cheap solution.</p>