Odd battery type dependence on my Electro 35 GT

[nthearle]

My Electro 35GT has always given accurately exposed negatives until today when I took a roll of Tri-X out of the tank to find the negatives over-exposed by about 2 stops. I'd followed my standard development regime, so I immediately tested the Yashica against my Canon A1's meter. Assuming the yellow light comes on at 1/30th, the Yashica was indeed metering at 2 stops over. The battery check light was nice and bright and the camera clunks when I wind it on. The previous roll had been accurately exposed. Testing the low light metering I noticed that at F16 it took much more than twice the time at F11 to close the shutter and that there was no 'siren whine' when the shutter was about to close.

I've always believed that the battery type (AgO, Li or alkaline) didn't really matter, other than alkalines might not light the battery test light. Nevertheless I removed the PX28 silver oxide in an adapter and tried the tests again with a new lithium PX28. The results were quite different - the exposure reading matched the Canon, low light test at F16 took about twice as long till the shutter closed compared to F11 and the siren whine reappeared.

I tried the silver oxide in my Canon, it fired the battery test LED at a good frequency and held the shutter open for a 4 second exposure OK. The open circuit voltage of the silver oxide battery was 6.38V (not that significant I know).

I can't explain these results at all. I wonder if anyone else can? Maybe the silver oxide can't drive the load on it, whereas the lithium one can? I find that hard to accept though, as it held the Canon's shutter open OK for 4 seconds. I'm puzzled.

 

[Dwig]

...as it held the Canon's shutter open OK for 4 seconds. I'm puzzled.

No it didn't. The Canon A-series don't work that way.

The battery does not "hold" those shutters open. They use a system where one electrical "pulse" releases the first curtain and, after a time, a second pulse releases the second curtain. The battery has to run the timing circuit for the duration but does not have to energize an electromagnet to hold the shutter open the way older, cruder systems did.

 

[ColSebastianMoran]

... I've always believed that the battery type (AgO, Li or alkaline) didn't really matter, other than alkalines might not light the battery test light. Nevertheless I removed the PX28 silver oxide in an adapter and tried the tests again with a new lithium PX28. The results were quite different - the exposure reading matched the Canon, low light test at F16 took about twice as long till the shutter closed compared to F11 and the siren whine reappeared.

I believe that the Electros are not sensitive to the battery type (and therefore the open-circuit voltage).

The real test for your camera would be to test again with a fresh PX28 silver oxide battery. Is your camera now sensitive to the battery type? Compare two fresh batteries to see.

Or is this particular silver oxide battery bad? I think this is more likely.

 

[nthearle]

Thanks for the info Dwig, it was useful.

I believe that they are not sensitive to battery voltage too ColSeb. It must be down to their current sourcing capability. I don't have a second oxide battery, but I do have an alkaline, which I have just tested in the Yash.

Firstly the alkaline came out of another Canon A1 in which it drove the test LED fairly slowly.

I tried a new Lithium, the alkaline and the silver oxide in the Yash closed down to F16 under fairly subdued room lighting. The lithium kept the shutter open for 20 seconds. The alkaline kept it open for 23 seconds. In both cases there was a whine rising in pitch just before it closed.

The silver oxide kept it open for over a minute (pointing at the same target), at which point I picked the camera up and pointed it at a bright light and then the shutter closed. It never whined.

The alkaline lights the battery test very dimly compared to the lithium and the silver oxide. The only conclusions I can reach are that the alkaline has the lowest open circuit voltage and that the oxide can't deliver the same current (necessary to charge the capacitor in the meter)as the other two but is OK at low current demands.

I guess a new silver oxide might be better. I also conclude that the battery test indicator isn't much of an guide to the battery's condition.

 

[Frontman]

I have had similar problems with PX28 batteries. I found that when using a PX28 battery in a CC, the camera would work, but the battery check lamp would not light up. When using a 4LR44 battery, the check lamp worked fine.

 

[ColSebastianMoran]

This is very interesting indeed. I'll test my two GX's (one from Frontman, delivered in person in Tokyo!).

The question: Do we find repeatable exposure anomalies using Silver Oxide batteries in the GX?