Weird light meter battery problem

bags27

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I bought a Gossen Superpilot GDS off a forum member and it works great. I had bought a 3-pack of WeinCell MRB625 for it--the expensive way to go, but the easiest.

I then bought a back-up meter ebay and it's got a very weird problem. It came with a 625a battery (the previous owner used it to test if it's working) and it did work with that battery, but of course, not exactly. But it does not work at all with any of the WeinCell 625's in it. I've tested them: they are fine. What could possibly be happening here?

many thanks.
 

xkaes

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I assume you are referring to a Super Pilot CdS, and who knows what the other meter is????? Without knowing what the other meter is how do you know it's the right battery?

We're not looking over your shoulder, so you need to give us all the details you can. Do you have a battery tested? Don't assume "new" batteries are A-OK.
 
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bags27

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1.It's a backup and, sorry, it's the same meter. Sorry for the typo, I meant CdS.
2. I wrote "I tested them." So, yes, the other two batteries in the 3 pack work. I tried each of them with the original meter I received and the meter meters exactly the same with each. So it's not the battery per se.
 

xkaes

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I use the Super Pilot SBC (Silicone Blue Cell) which is very similar, and I know that it's easy to put the battery cap on "wrong" and it won't work. Take a close look.
 
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bags27

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Thanks. I did that, too. Still doesn't work!
 

Harry Callahan

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I heard somewhere that these WeinCell batteries actually need air circulation, as they apparently need oxygen to work proper. Maybe your second light meter has some gunk around/in the battery compartment sealing air flow?
Maybe the battery contacts are dirty/oxidized?
 

xkaes

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Does the meter have a needle? I assume so. Sometimes these get stuck against the plate and can be pushed up slightly and released.
 
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bags27

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The meter DOES work with a 625a battery (though the 625a has slightly too high voltage for proper metering, right?) And the 625 batteries are new and work in the other Super Pilot CdS. But I'll try to clean the contacts anyway.

Thanks!
 

Xylo

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I don't know if it's related, but I have an old meter in which a wire that goes to the battery compartment had corroded away.
You might need to open it up and check.
If it's anything like the Gossen SBC I once too apart, if yours has a sliding range switch that has a positive click (it slides automatically from one end to the other when you pass the mid point), watch out as this means that there is a spring pushing outwards on the slider. This thing will just fly out leaving you really puzzled (ask me how I know).

The interior has a lot of space (from memory) so it would be easy to insert a cheap Chinese buck converter so you can use Alkaline batteries instead.

Personally, I've had mixed results with the Wein Cells. These things are expensive, slightly thicker than the originals and not always compatible with electronics. I have a Konica T3 in which the meter starts underexposing by 3 stops when I use those; I still don't understand why! All I know is that I had to Dremel the cap to fit them in.
 

xkaes

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Let me summarize -- and please correct me if I am wrong.

You have TWO Super Pilot CdS meters. Both of them work with a PX625A, but only one works with a Wein replacement.

If that's correct, I've got two questions:

#1: Do the two meters give the same reading using the PX265A?

#2: Does the meter that works with the Wein replacement give the same reading using the PX265A?
 
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bags27

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Thanks for taking the time to try to get to the heart of this. You understand the situation correctly.

But as to your questions, "accurately" and "inaccurately" are a bit relative. If a meter is ballpark accurate, then I'll try to adjust the back screw to get it within tolerance of an accurate reading. Even the "good" meter that I got from someone on this board required back adjustment.

Since the 625A can not give accurate readings, I haven't tried it on the otherwise accurate meter.

this is the situation. The 2nd meter works inaccurately but does at least work with the 625A it came with in that it reacts to bright and low light well, if inaccurately. But it does not work at all with any of the 3 tested Wein batteries: the meter remains dead. To me, this is completely weird.
 

MattKing

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The Wein batteries are very slightly thicker than others, which can matter.
And some equipment uses one face and one edge of the batteries as the two contacts, while other equipment uses both faces of the batteries as the two contacts.
So check the placement of the contacts in the non-working meter, and make sure that the Wein batteries have contact faces that match.
 
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bags27

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Thanks, Matt. I'll do that: bet it's something like that.
 

koraks

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In addition to what @MattKing says: zinc/air cells (like the Wein cell) can have a very low peak current draw capability. I don't know the internals of this particular meter, but if it has a capacitor in there somewhere and it happens to be leaky, this can result in a high current draw beyond what the zinc/air cell is capable of delivering. Other causes of abnormally high current draw are also conceivable. If this were my meter, I'd start by opening it up, cleaning it out and inspecting for corrosion, fouling & degradation, draft a schematic of the electronics, do some measurements and then decide on possible repairs. In other words - poke around a bit, see what's going on.
 
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