This would be my first thing to check. The difference in battery voltage wouldn’t make the readings that your experiencing. You’ve got another electrical issue. It could be a loose wire or corrosion somewhere, but potentiometers (or electrolytic capacitors if there are any) are the most likely culprits on old circuits. They combine exposed elements subject to oxidation and moving parts that create wear and tear.Sometimes the potentiometers give trouble; the wiper after sitting in one position for decades will oxidise at the point of contact; the fix can be as simple as moving the wiper and returning to original setting.
As for the meters being unreliable: Nikkormat FT 1966: Meter is accurate, ring resistor smooth. Nikkormat Ftn 1970 with signs of very extensive use: After cleaning ring resistor, meter is accurate. Nikon FTN: meter recalibrated for silver oxide cells, accurate. Nikon F2 (1972 with later DP11); accurate but camera and finder were overhauled before I got it. Nikon F2A 1979: Meter was apparently recalibrated for Beattie Intenscreen, it reads approx 2/3 to 1 stop low with Nikon screens or it just happened to drift into matching the intenscreen perfectly.
So they're not as bad as all that, after 38 to 51 years.
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More recently, I bought a camera outfit and the camera had a dead Wein cell in it. I was able to determine that all that Wein cell is is a 675 battery with an adapter set in place. I was able to knock the 675 out of the adapter ring with a few well-chosen whacks. So now I have a best way of getting my F's meter to work reliably. It was kinda hit-or-miss with the copper wire.
No, a Wein cell is a zinc-air cell, like hearing aid batteries!
You probably have a Criscam MR9 adapter Dead Link Removed
There is no such thing as a 'one fits all' compensation setting, because different light levels require different amounts of compensation. The best solution is 1.4V zinc-air hearing-aid batteries.Just got a 1969 F with Ftn meter. Have not tested it yet and I will use silver oxide 1.55V batteries. How much compensation will I need to do in ASA-steps to compensate for the higher voltage?
There is no such thing as a 'one fits all' compensation setting, because different light levels require different amounts of compensation. The best solution is 1.4V zinc-air hearing-aid batteries.
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No, sadly not. The only sure-fire solution would be a voltage regulator that drops the voltage, and the voltage regulator would also need to compensate for the fact that the voltage from the battery trails off as it depletes, hence the battery-check function in cameras that don't use mercury batteries.
It all seems a bit moot and over-thinking the problem when zinc-air ZA675 hearing aid batteries have been so readily available, for at least as long as mercury batteries have been banned, if not longer. If your camera or device takes the +ve from the rim of the battery instead of from the face, you possibly will need an adapter that expands the diameter of the ZA675 cell. They are cheaply available and are of course completely re-usable when your battery depletes.
I am not sure I follow you here. The 1.55V silver oxide battery, like the mercury battery, has a constant, albeit higher, voltage. So the meter deviation ratio must also be constant, regardless of the light level, and thus it would be possible to compensate with the ASA-setting, right? That's my theory.
Wilt, might your results have been different if you would have compared the 1.35v mercury cell against the 1.5v silver-oxide cell? The latter is reported to have discharge characteristics more similar to the mercury cell.
image from Dead Link Removed
The Photomic linkage to the lens index pin swipes across a linear potentiometer, and after five decades it is not surprising that there may be some built-up oxidation along the potentiometer. It might be useful to slide it back and forth a number of times to burnish the surface of the pot to decrease the amount of resistance which is being presentedTested the Nikon F now (that I mentioned above). The Photomic Ftn meter acts really strange. ...Compared to another reliable camera it is about 5+ stops wrong(!). Like if the other camera shows 1/125 and f 2.8 this says f16(+).
What do you think, could cleaning the resistor ring inside help?
Thanks, I will try that and also some deoxit cleaning.The Photomic linkage to the lens index pin swipes across a linear potentiometer, and after five decades it is not surprising that there may be some built-up oxidation along the potentiometer. It might be useful to slide it back and forth a number of times to burnish the surface of the pot to decrease the amount of resistance which is being presented
Damn, can't unscrew one of the 4 screws to get access to the ring resistor. The screw of the head got damaged (soft metal it seems) when i tried to unscrew it...The resistor is actually a ring. You meter is behaving oddly, reading way too high. That and the jumpiness makes me suspect the ring is worn out, but one can be sure only by measuring the resistance.
Cleaning it can do no harm, but please remove the ring from the finder - spraying Deoxit into the finder will only lead to a mess.
Not soft metal, your screwdriver doesn't fit. The blade must fill the slot, both width and thickness, and go all the way to the bottom of the slot. Otherwise it will twist out of the slot and damage the screw. Sometimes these screws are cemented, a tiny dab of acetone and a 20 minute wait will loosen thisDamn, can't unscrew one of the 4 screws to get access to the ring resistor. The screw of the head got damaged (soft metal it seems) when i tried to unscrew it...
Yes, I was in a hurry trying to get that screw out... there was some cement/laquer that secured the screw, and I guess the slot was filled so the blade didn't go all the way down. Now it's impossible to get it out I'm afraid.. What to do?Not soft metal, your screwdriver doesn't fit. The blade must fill the slot, both width and thickness, and go all the way to the bottom of the slot. Otherwise it will twist out of the slot and damage the screw. Sometimes these screws are cemented, a tiny dab of acetone and a 20 minute wait will loosen this
I'm also wondering if your finder could have been reassembled incorrectly, the error is in the wrong direction for bad Cds cells. The slight jumpiness is typical of a dirty ring, Deoxit will loosen some of the crud, what it doesn't remove can be removed with an eraser either the white Staedtler-Mars type or the tan Artgum that is cube shaped.
Yes, I was in a hurry trying to get that screw out... there was some cement/laquer that secured the screw, and I guess the slot was filled so the blade didn't go all the way down. Now it's impossible to get it out I'm afraid.. What to do?
The head of the screw is totally damaged so I can't get a grip at all.Clean the lacquer out of the slot and try a screwdriver that fits. IF the screwdriver fits correctly, you need only a very shallow slot. Use a loupe, and if you're in a hurry save yourself a lot of bother and throw it in the trash right now. Acetone will loosen the lacquer.
Unless you have the tools, skills, and experience to drill the head off and remove the stump from the cover of the prism, then find or make another screw, you have option a) get another finder, or option b) find a watchmaker to remove the screw.The head of the screw is totally damaged so I can't get a grip at all.
I guess alternative a) thenUnless you have the tools, skills, and experience to drill the head off and remove the stump from the cover of the prism, then find or make another screw, you have option a) get another finder, or option b) find a watchmaker to remove the screw.
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