35SP Meter Adjustment

[duckmcf]

Hi Gang,
Just a quick question for the collective.

Is the 35SP's meter adjustable and if so how?
That is, is adjustment made electrically via a potentiometer or mechanically via a physical meter zero-point adjustment.
Or is adjustment made by identifying and replacing resistors in the meter circuitry?

The reason I ask is that with a NOS V625PX Mercury battery (measured at 1.348V) my 35SP reads around 1EV under and with a Silver Oxide battery (measured at 1.58V) it's around 1EV over. :bang:

My work-around has been to use the mercury battery and set the ISO 1 stop faster (ie. set on 200 for 100 film), but an an electrical engineer it'd be really properly nice if I could adjust a potentiometer or a mechanical needle setting if either exists in the 35SP.

Anyway, I know long term I'll probably have to go down the Zinc-Air or diode/adapter/Silver-Oxide route, but for now I have a couple of NOS Mercury Oxide V625PX's 😎 which would be nice to use and so any direction you can give me on this would be very much appreciated.

Kind regards
Noel

PS I'm confidant with my EV measurements as I baselined the readings against an 18% grey card and my Nikon D90 which also correlated with the Sunny-16 rule under the clear and bright Australian summer sun.

 

[julio1fer]

My tech adjusted mine for alkalines. I am 95% sure he rotated the meter assembly mechanically, i.e. zero point adjustment.

Your SP will work nicely just with the ISO correction, though.

A side note, before the flood comes saying that alkalines have a variable voltage in the discharge curve: I know that. It happens that the SP takes less than 50 microamperes when metering (I have measured it). And that happens only when out of the case. So you may adjust it for 625 alkalines and live happily ever after. For peace of mind and less trust in physics, use a silver battery with adapter and adjust for it.

 

[duckmcf]

Rotating the meter assembly itself, that makes complete sense. An elegant and cost effective solution that's very typical of the Japanese.

Thanks very much for that. I've read dozens on times on the interweb that calibration to Alkaline or Silver-Oxide can easily be done by a camera tech as part of a CLA but until now I wasn't able to find out how it's actually done.

On the alkaline vs. silver oxide discharge front, yes I agree that due to the low currents involved if you change out the battery every other year it shouldn't be a problem.

I think the interweb folk see the various discharge curves and then get their collective nickers in a twist that there's around 2 stops exposure difference between 100% and 10% remaining capacity for the alkaline battery. What they don't also say is that 100% to ~70% equates to around 2 years of casual use.

All that said, the bottom line is that with Mercury Oxide or Silver Oxide you can more or less forget all about the battery until the meter stops working. With an alkaline it's probably wise to mentally check the meter's reading against the Sunny-16 rule every now and then to make sure that it hasn't discharged too much. Actually, given that we're talking about 40yo cameras that's something we all probably do already.

Finally, you mentioned that your meter draws 50uA. I also checked the draw on my camera and while I didn't note down the exact values I do remember that there's around a 10x increase in current draw from 5EV (~35uA) to 17EV (~400uA).

Thanks again for your reply.

 

[Solinar]

Look up "MR-9 Battery Adapter for Film Camera" on a eBay and be done with it.

You'll be able to use a standard 386 silver oxide watch battery.

Best Regards,

 

[duckmcf]

Look up "MR-9 Battery Adapter for Film Camera" on a eBay and be done with it.

You'll be able to use a standard 386 silver oxide watch battery.

Best Regards,

Yep, I could go down the MR-9 adapter route but given that I have 3x NOS V625PX Mercury Oxide batteries that are all in really good shape there's just no point for me right now.

However for others that don't have V625PX's on tap I agree that the MR-9 adapter is the way to go for a set-and-forget solution that the Zinc-Air batteries can't match.

 

[julio1fer]

Excellent, then. I measured discharge at shadow values so it is more or less close to your currents. 400 microamperes is still low.

I remember that my tech said that the meter rotation is accesible at the bottom of the camera, and not a very complicated thing to do.

Silver oxide batteries should be a good replacement of the mercury 625 (after adjustment), but the mercury one will last a lot in normal use, if you keep the camera in a case.

I would not recommend Zn-air batteries because they do die after a few months, whatever the discharge rate.

 

[duckmcf]

That's great that the meter can be rotated from the bottom as the bottom plate is really easy to remove.

I knew that the meter on the 35RC is at the bottom and is also adjusted from the bottom, but as the 35SP's meter is up top I assumed that adjustment for that camera's meter would also be up the top.

Anyway, when I finish the current roll of film, I'll have a look under the bottom plate.

Thanks again for all your help.

Cheers
Noel

PS I crunched some numbers for a 450mAh V625PX and you're right it should last a very long time with the case on.

 

[Max Pegler]

If you want to send it up to Sydney, these guys did mine with a CLA, all good.

http://www.cameraservicecentre.com.au/

Regards
Max P

 

[gma]

I just had the bottom plate off my SP, but there's no sign of anything resembling a rotatable meter under there. Has anybody adjusted their SP's meter successfully?

Cheers.

 

[duckmcf]

I just had the bottom plate off my SP, but there's no sign of anything resembling a rotatable meter under there. Has anybody adjusted their SP's meter successfully?

Cheers.

Hi,
Same here. I've had the bottom plate off my 35SP and there's nothing there that's vaguely associated with the meter.

I've Googled around the web quite a bit and have come to the conclusion that the meter to be rotated is under the top plate on the 35SP. Interesting it looks like the 35RC has the meter under the bottom plate which is where any confusion my have come from.

Anyway, so far I haven't worked up the courage to take the top plate off my 35SP. It currently works very well and is in great condition and so I'd hate to ruin it simply to fix a problem that I can work around by setting the ISO a bit higher.

Cheers
Noel

 

[duckmcf]

Hi Gang,
Just a quick post to close the loop on this one.

It was time for my 35SP to have a CLA and so I asked the tech to calibrate the meter while they were in there. When I asked if this was done by rotating the meter he really winced. For whatever it’s worth his view is that (on the 35SP at least) the meter is adjusted by changing out the appropriate resister/s and definitely not by rotating the meter.

Anyway, the camera came back with an amazingly clear view finder, super smooth focusing, a sharp as a tack rangefinder spot, and a meter that’s usually within half a stop when compared with my Nikon’s Matrix meter.

Happy days....

 

[Trius]

Hi Gang,
Just a quick post to close the loop on this one.

It was time for my 35SP to have a CLA and so I asked the tech to calibrate the meter while they were in there. When I asked if this was done by rotating the meter he really winced. For whatever it’s worth his view is that (on the 35SP at least) the meter is adjusted by changing out the appropriate resister/s and definitely not by rotating the meter.

Anyway, the camera came back with an amazingly clear view finder, super smooth focusing, a sharp as a tack rangefinder spot, and a meter that’s usually within half a stop when compared with my Nikon’s Matrix meter.

Happy days....

Which tech did you use?

 

[duckmcf]

Which tech did you use?

Shutter-box in Toorak rd. Camberwell, Victoria, Australia.
I couldn't be happier with their service and the quality of their work.
They're really terrific and very nice people. 🙂

 

[julio1fer]

Good to know this. So it is electrical adjustment not rotation. It may be done, anyway.