Relpacing mercury batteries in older equiment

[Eric Rose]

Ok call me a crank, but I like the older mechanical equipment like Nikon F2's and Canon F1's etc. None of that wizzy stuff for me. And I'm not even going to get into the MF and LF gear I have. All mechanical. Still works when the battery goes dead. Now try that with the new elecronic marvels.

Anyway I digress, one of the disadvantages of using this old stuff is that they were designed to operate with 1.35v mercury batteries. Something our enviromnent I guess really doesn't need in the landfills. The new replacement batteries are 1.5v. Hence incorrect readings.

I did some searching on the net and Photo.net and found the MR-9 appliance as well as the Wein battery alternatives. I also found some had used a 675 battery with washers to replace the 625.

I meandered over to my local Radio Shack with my old Gossen LunaPro and proceeded to try different battery combinations. Tried the 675's and when I hit the battery check it was well short of the required spot. Funny considering they are 1.4v batteries (needs 2). Horsed around with other batteries and finally settled on the 625's at 1.5v each.

When I did a battery check it was just over the sweet spot. I then compared results once I got home to my Pentax Spotmeter and a Zeiss meter. It was only about 3/4 of a stop high. That's an easy compensation to live with.

Now to my question. I would rather get inside this little beasty and rework the wheatstone bridge or whatever it uses with new resistor values so it will read accurately with the newer batteries. Does anyone have a repair manual or wiring diagram they can share with me that would allow me to accomplish this?

The meter is not worth taking it into a repair shop to do something I can do myself.

Any help would be greatly appreciated. Also does anyone have any first hand experience with these MR-9 adapter thingies? I've heard pros and cons on them.

Eric

 

[Robert Kennedy]

I'm like you. I LOVE the old stuff. I have an old F2, and FT and an FT2. Guess which one is easiest to get batteries for....

I feel your pain of course.

In my experience though, there is little you can do. I tried those nasty Wein cells. They simply DIDN'T work at all. The adapters seem dodgy and I am a bit wary of them.

You know what seems to work best?

Those 1.5v batteries. I have an old Pentax Spotmeter that uses a 1.35 and a 9 volt (why, I have no idea....). I finally gave up and used a 1.5V.

It works perfectly. I used it on some 4x5 Velvia chromes and it came out fine.

 

[David A. Goldfarb]

On the other hand on my Canon EF, the meter won't read at all with 1.5v cells. I use the Wein zinc-air cells and just always keep spares on hand for when they run out. Best price I've found for them is at bhphoto.com.

 

[BobF]

This site has a workaround for Minolta SRT that might be of interest.

http://www.pcisys.net/~rlsnpjs/minolta/mercury.html

I only have one camera with this problem and just use the 1.5v or a handheld lightmeter. The in camera meter with the 1.5v doesn't seem that far off but I haven't really checked it that closely as I only use it for close ups with strobes.

 

[Eric Rose]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (BobF @ Nov 27 2002, 06:53 AM)</td></tr><tr><td id='QUOTE'>This site has a workaround for Minolta SRT that might be of interest.

http://www.pcisys.net/~rlsnpjs/minolta/mercury.html

I only have one camera with this problem and just use the 1.5v or a handheld lightmeter. The in camera meter with the 1.5v doesn't seem that far off but I haven't really checked it that closely as I only use it for close ups with strobes.</td></tr></table><span id='postcolor'>
Wow that site is amazing! Thanks. Being an electrical type I will certainly delve into this project!

Eric

 

[Hilm3]

Adorama sells a kit for the old Gossens. I bought one and it works great. It is basically a plastic cylinder with a metal bottom and some circuitry inside that converts to the right voltage. My Luna Pro is accurate again.

Gossen Luna PRO S Battery Replacement Kit #4145:

Dead Link Removed

 

[Flotsam]

Does that replace two Mercury 625s? I wonder if it could be used in an F Photomic prism.

 

[Hal Bissinger]

The nice thing about mercury batteries is (was) that they have a flat discharge curve- the voltage remains constant almost until the end. Zinc-air and alkaline among others do not do this. The voltage gradually declines throughout their useful life.

This means that even if you were able to recalibrate (or compensate) your meter for the higher initial voltage, the accuracy will change unpredictably as the battery ages.

Best bet, if you are using a PX13 or PX625 is to use a MR-9 adapter which is a voltage regulater that works together with an easily obtained 386 watch battery to provide the required constant 1.35v.

C.R.I.S. Camera Services (Dead Link Removed) also has other similar adapters for the replacement of PX27 and PX32 batteries.

 

[dr bob]

Equipment using a bridge circuit and a "match needle" mechanism should work just as accurately with any power source provided the voltages is not extremely high (or low). These circuits employ a null point to operate and only require a source of power. I have a tiny Vivirar meter, which states that it can use either mercury or Ag/Zn type provided the physical size is compatible. My experiments verified this. My old Pentax Spotmeter camera (the one with screw-on lenses) can also use either.

Truly, dr bob.

 

[tleirtro]

I bought a few Mercury batteries for my Canon FTb from www.px625.com
Seems to work just fine.

Thor Egil

 

[hidesert]

I found the Wein zinc-air replacements did not work in my old Nikon Ftn but worked well in my Gossen Sixtar (Super-Pilot). Go figure.

 

[Chan Tran]

MR-9 waistes battery power. Zinc Air cell loses its charge quickly. Silver Oxide or Alkaline do not have flat discharge curve so if recalibrate accuracy changes as battery ages.
So I would simply not power these devices and use them san power. Who needs a meter especially one that is not very accurate.

 

[mikebarger]

Sure glad I've got a slug of mercury batteries in the freezer. Unless they end up going bad, I've got a lifetime + supply.

Mike

 

[Arvee]

I've used the Gossen Battery Adapter with two 1.5V Silver oxide cells in a coupla applications (Weston Ranger 9 meter, the Gossen LP), and they worked just fine. I would think they would work in most applications where two 1.35V mercury batteries are required.

 

[Ralph Javins]

MR-9 waistes battery power. Zinc Air cell loses its charge quickly. Silver Oxide or Alkaline do not have flat discharge curve so if recalibrate accuracy changes as battery ages.
So I would simply not power these devices and use them san power. Who needs a meter especially one that is not very accurate.

Good morning, Chan Tran;

Sir, I cannot agree with one of your comments about the discharge characteristics of the Silver-Oxide (Ag-O) battery chemistry. The criticism about the alkaline batteries is valid, but not for the Silver-Oxide.

Of the battery types available to us today, the Silver-Oxide most closely approaches that of the old 1.35 VDC Mercury (Hg) batteries, although at a slightly higher voltage of 1.5 VDC, but the discharge curve is almost equally flat. If a recalibration is necessary (but it will not be needed in almost all cases where an adapter is used), that calibration will remain valid for the entire flat portion of the discharge curve.

Then there is the point about the forward biased Schottky Barrier Diodes in the MR-8, MR-9, and other battery adapters to provide the close equivalent to the Mercury battery voltage of 1.35 VDC, or a multiple of that. This approach is superior to the use of a voltage dropping resistor to achieve that effect, and is much more efficient. It is our most cost effective way today to work around the banning of the old Mercury batteries when used with the Silver-Oxide batteries we can buy today.

 

[Athiril]

unfortauntely my Yashica only seems 1/3rd of a stop under-exposed on the meter with a 1.5v battery.. can compensate, but I'd like 1 or 2 stops... seeing as ISO set on camera for metering for goes down to 25 but only up to 400.

 

[rjbuzzclick]

I just bit the bullet and bought the MR-9 adapter from C.R.I.S. I've had no problems with it.

 

[Steve Smith]

Equipment using a bridge circuit and a "match needle" mechanism should work just as accurately with any power source provided the voltages is not extremely high (or low). These circuits employ a null point to operate and only require a source of power. I have a tiny Vivirar meter, which states that it can use either mercury or Ag/Z

Whilst I agree with what you are saying, a bridge circuit will use a meter where the needle in the centre indicates correct exposure. I would not refer to this as 'match needle'.

If your camera's meter indicates correct exposure with a central position and the meter needle rests at that position when switched off then it is very likely that you have a bridge circuit which will tolerate voltage differences.

If your exposure is set by moving one needle (or other indicator) to match the position of the meter's needle then it is not a bridge circuit and will be affected by voltage variations. This type of circuit will also have the meter needle return to one end of its travel when switched off.

For the latter type which need 1.35 volts, I think the best solution is to use a 1.5 volt silver oxide cell and have a schottkey diode internally wired in series with the cell connections.


Steve.

 

[John_Nikon_F]

Dia,

I agree with Ralph. The silver batteries are about as close as you can get to a mercury battery in voltage curve. So, as long as you compensate for the voltage difference - I find that a Nikon body that originally ran mercury will read about 2/3 of a stop too high on a silver or alkaline battery - or you have the gear recalibrated and use a silver battery in either case, you'll have consistent readings for quite some time.

With respect to the MR-9 adapters, Robert Decker does not recommend them for the F Photomic FTn finder. At certain EV values, the meter uses too much current than the MR-9 can handle. He says that recalibration is the only way to go. I did this on my F FTn's meter, and have to say that the batteries in it, which are about 18 months old at least, are still fully charged and allow the meter to provide an accurate reading. The needle still deflects a little over correct exposure when I depress the battery check button.

Same with my black Nikomat FTn, which I had recalibrated about a month ago to 1.5 volts. Matches my chrome FTn which is still running a nearly new mercury PX625 (thanks mgb74, btw). All three cameras match my F2A and my FM2n. My F3, due to it having more of a spotmeter, can vary a bit compared to the rest of the bodies. The only body that I haven't compared them to is my FT2, which, prior to a week or so ago, was off a stop and had a very erratic meter. Now is overhauled and awaiting pickup.

Nikon CdS meters in manual exposure bodies typically are just center-needle meters (or in the case of the DP-2 finder, center-diode - like the FA and the F3), whereas the EL and the ELw use a match-needle system, like the later EL2, FE, FE2, FG-20, and FM3a.

-J

 

[benjiboy]

On the other hand on my Canon EF, the meter won't read at all with 1.5v cells. I use the Wein zinc-air cells and just always keep spares on hand for when they run out. Best price I've found for them is at bhphoto.com.

As you are probably aware David the EF is unique in that it has a self- regulating metering and should work correctly with 1.5 volt alkaline cells,http://en.wikipedia.org/wiki/Canon_EF_camera, mine works fine with these even shooting velvia 50. I'd get it checked if I was you, I've tried Wein Zinc- Air Cells but find they don't last more than a couple of months, and are very expensive

 

[Yeeski]

The 675 zinc-air hearing aid batteries work fine in my F-1n. I ran some Kodachrome 25 last year with no exposure problems. Be aware that, once you remove the tape from a zinc-air battery, it takes a while for it to reach full voltage, perhaps an hour or so.

 

[benjiboy]

This company in the UK sell a cheap solution to the problem that allows you to use hearing aid batteries with a purpose machined adaptor.
http://www.paulbg.com/px625uk.html

 

[Steve Smith]

On the other hand on my Canon EF, the meter won't read at all with 1.5v cells.

Probably a silly question and I apologise in advance for its patronising quality!

Did you put the 1.5v cell in the right way round? If you look at the cells, the logical way to insert an alkaline or silver cell is actually the wrong way round. The large part (end and sides) of a modern cell is the positive connection. This would be negative on a mercury cell.

That is way they usually need some tape or a rubber 'O' ring to insulate the sides (apart from making it a comfortable fit).


Steve.

 

[benjiboy]

Probably a silly question and I apologise in advance for its patronising quality!

Did you put the 1.5v cell in the right way round? If you look at the cells, the logical way to insert an alkaline or silver cell is actually the wrong way round. The large part (end and sides) of a modern cell is the positive connection. This would be negative on a mercury cell.

That is way they usually need some tape or a rubber 'O' ring to insulate the sides (apart from making it a comfortable fit).


Steve.

Rubber "O" rings won't work with the Canon EF Steve because the batteries in that particular camera need to make electrical contact all the way round, and. need to be of a conductive material like Copper.

 

[benjiboy]

If I have any of these mercury alternative batteries in my camera I check it against a Kodak grey card, with a meter of known accuracy and adjust the I.S.O. to match before I take it out to shoot, because the battery discharge characteristics change over time.