Nikon F Photomic Meter way off (i think?) with 1.5v batteries

E. von Hoegh · Dec 11, 2017

They show up pretty regularly for sale, cheap. Some will be ok, but many will have dead/dying Cds cells and/or bad resistors. Virtually all will need service of some sort, keep in mind that they are all getting close to 50 or more years of age. I have one good one which I use only for macro work where TTL metering is a real convenience. Now that I have a couple F2As, both with good meters, i guess it can die if it wants.
Check Sover Wong's website, he may have some options. He's located in England.

cooltouch · Dec 11, 2017

I have successfully cut a slot in screws that I've managed to bugger up, a slot deep enough where I can use just a flat-bladed screwdriver to unscrew it. Just a thought -- if you can reach it, that might be an alternative for you.

The proper screwdriver to use on all cameras is not a Phillips. It's called a "cross-point" (according to a camera repair teacher I had). It's easy to see the difference between a cross-point and a Phillips. A Phillips has a long pointy head, whereas the cross-point is more blunt. It's very easy to strip a camera screw's head if you try to use a Phillips on it. Typically the screwdrivers you get in those ubiquitous jewelers sets are cross points.

Exopix · Dec 11, 2017

cooltouch said:
I have successfully cut a slot in screws that I've managed to bugger up, a slot deep enough where I can use just a flat-bladed screwdriver to unscrew it. Just a thought -- if you can reach it, that might be an alternative for you.

The proper screwdriver to use on all cameras is not a Phillips. It's called a "cross-point" (according to a camera repair teacher I had). It's easy to see the difference between a cross-point and a Phillips. A Phillips has a long pointy head, whereas the cross-point is more blunt. It's very easy to strip a camera screw's head if you try to use a Phillips on it. Typically the screwdrivers you get in those ubiquitous jewelers sets are cross points.

This screw was not Phillips or cross-point but a regular old slotted one.
What tool do you use for cutting a new slot in damaged screws?

E. von Hoegh · Dec 11, 2017

cooltouch said:
I have successfully cut a slot in screws that I've managed to bugger up, a slot deep enough where I can use just a flat-bladed screwdriver to unscrew it. Just a thought -- if you can reach it, that might be an alternative for you.

The proper screwdriver to use on all cameras is not a Phillips. It's called a "cross-point" (according to a camera repair teacher I had). It's easy to see the difference between a cross-point and a Phillips. A Phillips has a long pointy head, whereas the cross-point is more blunt. It's very easy to strip a camera screw's head if you try to use a Phillips on it. Typically the screwdrivers you get in those ubiquitous jewelers sets are cross points.

"Cross point" is a generic term there are JIS, Phillips, Reed & Prince, and maybe a DIN type. Japanese cameras with crosspoint screws use a JIS driver. I believe all Fs and finders use slotted screws, as do the first few years of F2s; they went to the JIS crosspoints in the 70s sometime.

E. von Hoegh · Dec 11, 2017

Exopix said:
This screw was not Phillips or cross-point but a regular old slotted one.
What tool do you use for cutting a new slot in damaged screws?

A screw-slotting file. I don't think your screws are accessible this way. It's also possible to carve a slot with a graver.

cooltouch · Dec 11, 2017

What E. said. Problem with most cross-point screws is they're also countersunk. Getting down in there without buggering up everything else will be difficult. Honestly, I think your best bet if you want to do it yourself is to get a small drill and drill off the head. You can probably rob a screw off a parts camera. Surely you must have a parts camera laying around?

E. von Hoegh · Dec 11, 2017

cooltouch said:
What E. said. Problem with most cross-point screws is they're also countersunk. Getting down in there without buggering up everything else will be difficult. Honestly, I think your best bet if you want to do it yourself is to get a small drill and drill off the head. You can probably rob a screw off a parts camera. Surely you must have a parts camera laying around?

OK, if I were doing it I'd use about a #65 drill, which is .035" diameter, actually I'd measure one of the other screws and select a drill about .002" larger. I'd pip a starting spot in what's left of the screw with a sharp pointed graver, drill into the head until it was just free of the shank, cut a slot in the end of the screw stump, soak the screw with acetone for a while and turn it out with a screwdriver. Sounds simple, right? It's easy when you have the tools and the skills to use them, impossible when you don't. I've been working on tiny mechanisms - think watches, tiny watches when necessary, for going on 40 years One restoration job involved making a new escapement for a very small ca. 1800-1810 form watch with verge escapement. The escape wheel was .079" dia, of contrate form, and had 13 teeth. I also made the cutters to cut the wheel.

Exopix · Dec 11, 2017

cooltouch said:
What E. said. Problem with most cross-point screws is they're also countersunk. Getting down in there without buggering up everything else will be difficult. Honestly, I think your best bet if you want to do it yourself is to get a small drill and drill off the head. You can probably rob a screw off a parts camera. Surely you must have a parts camera laying around?

Thanks. I will try with a small drill. Let you know if it works.

John Koehrer · Dec 11, 2017

E's solution is also yours. But once the head is gone you should be able to pop the cover off. When it's off, grab the protruding bit with a pliers & unscrew it.

Exopix · Dec 12, 2017

Managed to get away the damaged screw. Opened it and cleaned the ring resistor with isopropyl. Seems like it is less jumpy now and also more accurate; about 2-2,5 steps wrong instead of 5 steps. What about the trim potentiometer for the meter. Can I use that to compensate for the wrong meter level?

E. von Hoegh · Dec 15, 2017

Exopix said:
Managed to get away the damaged screw. Opened it and cleaned the ring resistor with isopropyl. Seems like it is less jumpy now and also more accurate; about 2-2,5 steps wrong instead of 5 steps. What about the trim potentiometer for the meter. Can I use that to compensate for the wrong meter level?

Nice! Could you tell precisely how?

E. von Hoegh · Dec 15, 2017

cooltouch said:
What E. said. Problem with most cross-point screws is they're also countersunk. Getting down in there without buggering up everything else will be difficult. Honestly, I think your best bet if you want to do it yourself is to get a small drill and drill off the head. You can probably rob a screw off a parts camera. Surely you must have a parts camera laying around?

Crosspoint screws. I was at a friend's house this morning and needed a pliers to do something, he gave me a cased set of miniature tools. In that set was a "0000 Phillips" screwdriver, upon inspection it turns out to be a JIS standard, definitely not Phillips. Interesting, perhaps purchased in bulk, labeled with what Americans are familiar with? I dunno. I tried it in the baseplate screws on my late F2, it fits perfectly.

Exopix · Dec 15, 2017

E. von Hoegh said:
Nice! Could you tell precisely how?

Drilled away the screw.
What do you say about the potentiometer?

E. von Hoegh · Dec 15, 2017

Exopix said:
Drilled away the screw.
What do you say about the potentiometer?

What size drill, and did you damage anything else?

As for the resistor ring, I'd have to find the schematic of the meter and see what's going on. I don't remember with confidence if it is a potentiometer or a rheostat. Give me time, I'll respond.

Exopix · Dec 15, 2017

E. von Hoegh said:
What size drill, and did you damage anything else?

As for the resistor ring, I'd have to find the schematic of the meter and see what's going on. I don't remember with confidence if it is a potentiometer or a rheostat. Give me time, I'll respond.

I mean the trim potentiometer on the upper side of the meter head. There is one for adjusting the meter and one for the battery check.

Exopix · Dec 28, 2017

Exopix said:
I mean the trim potentiometer on the upper side of the meter head. There is one for adjusting the meter and one for the battery check.

Anybody know if it's possible to adjust the trim pot to compensate for the wrong meter level?

E. von Hoegh · Dec 28, 2017

Exopix said:
Anybody know if it's possible to adjust the trim pot to compensate for the wrong meter level?

Which Photomic do you have?
The trim pot will let you tweak it, I'm not sure if you'll get 2 or more stops with linearity though. The CDS cells age and lose linearity, in some (all?) Photomics there are two internal potentiometers to correct this, but beyond a certain point you'll need new cells.

Exopix · Dec 28, 2017

E. von Hoegh said:
Which Photomic do you have?
The trim pot will let you tweak it, I'm not sure if you'll get 2 or more stops with linearity though. The CDS cells age and lose linearity, in some (all?) Photomics there are two internal potentiometers to correct this, but beyond a certain point you'll need new cells.

It is a DP-1.

E. von Hoegh · Dec 28, 2017

Ah. So it's an F2 not an F. There's a service manual on the web somewhere. The DP-11 is identical save for the aperture coupling mechanism.

Exopix · Dec 31, 2017

E. von Hoegh said:
Ah. So it's an F2 not an F. There's a service manual on the web somewhere. The DP-11 is identical save for the aperture coupling mechanism.

Sorry, it's a Ftn meter for this Nikon F. I have a F2 as well and I mixed them up.

Nikon F Photomic Meter way off (i think?) with 1.5v batteries

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