Fix Old Cameras: Nikon Photomic FTN Meter Modification
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- เผยแพร่เมื่อ 8 ก.ค. 2024
- Nikon Photomic FTN meter modification for use with modern batteries. This tutorial video shows how to partially disassemble the FTN Photomic meter prism and install a voltage dropping diode so the silver and lithium batteries can be used and maintain meter function.
classic camera repair - www.phototronic.biz
A few tools and books - www.amazon.com/shop/fixoldcam...
Your videos are a pleasure to watch even without a repair in mind. I hope that you will continue posting. Thanks!
Thank you for your words of encouragement and your interest in FOC.
Just finished this mod and turned my dead Ftn finder into a functional, accurate light meter. Thanks so much!
I like how the new edits show repairs are rarely perfect! Great video
+Shawnee Union
Thank you. Your comments are always appreciated.
Excellent! Just what I needed to know to fix my two beautiful condition Photomic meters.
Many thanks
Leslie.
Followed the instructions and did the same with mine. Worked great. Easier to work with than the F2 finders.
Excellent to hear of your successful repair.
Wonderfull work! Thanks a lot!
Wrapping up the video by playing the blues made my day!
Congratulations!!!
Very Good!!!
Thank you for your interest in Fix Old Cameras.
Great video! Can the diode be installed in series with the rear terminal connecting the blue wire?
thanks for the video. thats amazing.
Your comments are appreciated.
Thanks for the video FOC. I tried to use the IN4007 diode with cathode in right position (i used the voltage meter to see if the voltage is dropped or not -> get the right position of diode to the circuit). Unfortunately, it was unable to work when i installed the batteries and clicked on battery check button. The needle was not moved. In my case, i used the 2 Maxwell LR44 1.5V batteries. The voltage before regulating was around 3 - 3.1V and then after regulating was around 2.8 - 2.9V. Was it correct voltage for the meter to work properly ? Should i use another diode or replace the alkaline batteries by silver oxide batteries ? Thank you so much.
I recently acquired a Nikon Ftn Photomic, vintage 1971 from what I can ascertain from the camera body serial number. The finder on it came with batteries installed and the meter is working. However I did run into meter readings being about 3/4 stop off from meter readings taken of the same subject, same lighting, and same lens as my Nikon FM. (took readings off of an 18% grey card). That I attribute to the modern equivalent batteries installed in the Ftn finder. Since I don't feel like getting into the guts of my Ftn finder, I simply 'fudge' the film speed ASA so the Ftn meter reading agrees with that of my FM and my digital camera. However this is an interesting informative video and I'll bookmark it in case I get brave and want to do a long term permanent fix to enable me to use modern batteries without having to often check the Ftn meter against my other camera light meters.
Thank your for your detailed comments and for your interest in FOC.
Awesomeness!
Hello! Thanks for the video! Very helpful. I wanted to ask, my particular finder has a lot of play in the speed dial(even after having it CLA'd)not in setting the speeds but just in the way the assembly sits in the meter head body....is there a way to "snug" it up?
Beautifully done
Thank you.
@@FixOldCameras i wanted to ask, is it a relative impossibility to clean dust out of the viewfinder/prism area? Been using my new-to-me F for only about 3 days and it seems my wool coat has shed into the finder somehow😬
@@sLOMO_77 No impossible at all. Dust or wool behind the eyepiece can be accessed by removing the cover shell of the prism you can also remove the prism from the housing if need be. The viewfinder screen can be separated to access and clean as needed.
@@FixOldCameras this goes for the Ftn head as well?
Hi, I just saw your tutorial and I have been impressed by your professionalism, a pleasure to follow people who share interesting things. I have a Nikon F 2 and the light meter is not working. The question is, is the function of the photometer that does not work from the head on top, or is it an internal problem of the camera? Is it possible to use this technique from your tutoring, for my camera too? If so, what diodes do I need specifically?
Excellant!
Well Done, makes me wish I had one of these old prisms. FYI I use 3M Adhesive Transfer tape #465 clear to attach leatherette. Last time I checked it's available on Amazon. It is expensive over $50 for a 60 yard roll (1.83" wide). The good part is my roll has lasted over 20 years and still as sticky as when new. The tape is a mere. .002 inches thick. It may be available elsewhere, Grainger?
+Tom Heckhaus
Great suggestion, the transfer tape is really good stuff albeit pricey, but a 60 yard roll will cover a fair amount of leatherette.
Great video. I have a different issue with my ftn. The aperture pin won’t engage properly! I removed the front plate and a spring popped out! Maybe thats why it doesn’t work. For the life of me i cannot figure out where this spring goes. Can you offer any guidance? Thanks so much!
Excellent Video, thank you.
Will this same diode and method work on even earlier photomic prisms?
+Jim Stepanik Indeed it will.
What type of adhesive did you use to install leatherette cover? Love your videos. Replaced light seals in my rb67. Thanks
Pliobond. Also, in cases where the leatherette is not curling at the edges a permanent office glue stick works nicely and allows for easier removal if need be.
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Heyo, I have a pentax k2 that is jammed in the sense that the shutter refuses to close and it is stuck open. Any idea what maybe wrong? (Electromagnet, etc.) Thanks!
Hi 2 questions after watching this excellent guide. What glue do you use, and do you know what disassembly is required to clean a lot of dust build up behind the view finder glass. I wear glasses and the dust build up is quite noticeable and even more so when I shine a modem led light source into the prism whilst looking through the view finder. Thanks in ad advance.
Pliobond glue for most all applications. ( astore.amazon.com/fixoldcam-20?node=1&page=5 ) You may use a Permanent Glue Stic to adhere flexible light weight leatherette such as found on the Photomic meter prism. The disassembly to access the viewfinder glass should be fairly intuitive once the outer shell is removed.
I've modified a half-dozen cameras, including a Nikkormat FTN and several FTN heads with germanium and other diodes. After shooting my modified FTN meter heads with film, I'm not happy with the modification because it clearly does impart a non-linearity to the meter response; the voltage drop provided by the diode varies with current demands in the meter. For example, the meter is right on at EV9, but at higher EV, I found the exposure is off by a stop or more. I'm back to looking for equivalent new replacement CdS cells that will facilitate adjustment of the meter circuit without adding a diode. I'm now removing the diodes from my light meter circuits.
The vintage ECG109 germanium diode has proven to do very well in most single battery meter circuit applications that do not already have voltage regulating circuitry. The double battery circuits do not always do as well with the IN4007 silicon diode. Hopefully your search for a better fix is spot on.
Thank you for posting these instructions - very informative. I followed them to install the diode but probably did something wrong. The battery check is working as it should. However, when I turn the meter on, the needle shoots all the way to the left (indicating over-exposure), and stays there irrespective of ISO, shutter speed or aperture settings. Any idea where things may have gone wrong? Thanks!
If the battery check works as it should you did the install correct. Check the wiring around the CDS cells and the CDS cells themselves. An ohm meter would helpful.
Do you know how to remove dust inside of focusing screen of AE-1? AE-1P is relatively simple just pushing the button but I don't see how when it comes to AE-1.. And as always thank you for your tutorial video i really appreciate it.
+Paul love
The AE-1 prism is sealed and buried under the upper flex circuitry making it a major under taking to get to the focus screen. And unfortunately, over time, the "sealed" prism still manages not to stay pristine.
You can clean dust and fungus off these old prisms correct?
Amazing video. My Nikon f3 reads two stops over as compared with the external light metre.I don't know how to fix it.I also checked exposure compensation dial which is on '0' . I don't know how to fix it. Do u think all the Nikon f3 is like that? Any suggestions would be very helpful.
No they should be a little closer to the same reading. You must triangulate or confirm the accuracy of the hand held meter. onece the accuracy of the source meter is confirmed. Try to determine if the exposures of the F3 in question are also two stops off as well.
can you guys do a video on a Bronica Zenza S? i just bought one thats in decent condition and i don't know much about it but from what I've seen your videos are really great and i would like to see what repairs that particular model tends to need over time. thanks!
+MrMoisesramirez12 Thank you for the suggestion. The FOC request list is long and the Bronica Zenza S is now on it.
What's the most likely cause of failure to the light meter on a Photomic FTN finder?
How about a f3 light replacement. I was thinking a a micro led and a resistor....
Kind greetings,
Will there be an issue if a 1.5volt battery is used to power the light meter of a Nikkormatt FT? Will it have a negative affect on the camera?
All the best,
Your long time fan, Nick.
Which diode is used?
Do you use an adhesive to replace the leatherette cover?
Thanks.
The 1N34A diode is germanium diode as is the SK3080 that was used in this application. The SK3080 , used in this video, gave the voltage drop needed. If you do not get the voltage drop needed with a diode used you will not hurt the meter circuit. Double sided tape or some type of removable leather adhesive can be used to reapply the leatherette covering.
Some recommended options here - astore.amazon.com/fixoldcam-20?node=1&page=5
Can the Silver 625 batteries be installed without an adaptor?
The silver battery has steady discharge rate similar to the mercury battery, but the original px625 mercury battery was rated at 1.35 volts.
Mercury oxide batteries typically had a voltage of 1.35 Volts. They kept this voltage constant over their entire lifespan and lasted for years. They could be recycled and even recharged a couple of times. Question… Why is mercury acceptable in CFL light bulbs but not in batteries?
Silver oxide batteries typically have a voltage of 1.55 Volts. They also keep their output voltage quite constant over the entire lifespan of the battery and they have relatively long useable life.
Zinc-air batteries mainly for hearing aids have a constant voltage output too, typically 1.4 V. Since their voltage is close to the voltage of mercury oxide batteries, they can be used as a substitute without making any changes on the meter circuits. They are cheap… but they have a short life span of only 2 to 3 months, not depending on usage. Once their seal is removed, they dry out inevitably, even when not used. When first taken into service, new zinc-air batteries need quite a long time of approx. half an hour up to one hour until they achieve their correct output voltage. In this time they can cause incorrect meter readings.
Wein Cells from photo equipment dealers are basically zinc-air batteries with fewer ventilation holes to achieve a longer lifespan (approx. 6 to 12 months), as they do not dry out as quickly as normal hearing aid batteries. They have a smaller maximum power output than zinc-air batteries, but for photographic equipment this is not a problem, as the meters do not need much power. Wein Cells are still expensive and can be difficult to get in some places. They have the same problem with the initial voltage as normal zinc-air batteries.
Alkaline batteries have an output voltage that drops continuously over the lifespan of the battery, as it discharges - depending on the battery brand the initial voltage is approx. 1.6 volts - 1.5 volts. They are not a good substitute for the mercury oxide batteries because of the voltage drop over its lifespan.
-
Some of the later classic cameras using the 1.35 volt mercury battery have compensation circuits and are not affected by substituting a silver battery.
Did you use a zener diode is the ref: IN4007 for this or is that for a normal diode?
a vintage gerrmanium diode is used... however, if you have other diodes available, they can be tried to see if the desired voltage drop results. You will not harm the meter circuit if the voltage drop is incorrect.
Hello, I recently picked up one of these cameras and everything seems to work minus a little bit if either dust or fungus in the prism itself. Do you think it is possible to pull it apart to fix it or is it a lost cause?
By no means a lost cause. What looks to be fungus in a viewfinder is often de-silvering of the prism. Dust removal should not be to difficult as prism removal is fairly straightforward once the top cover has been removed.
Hell ya
Hi. I just got my hands on an earlier Nikon F photomic prism which looks like it has a lens or "eye" sticking out of the left side. Does this video also apply to the earlier prisms?
Yes the meter can be successfully modified in a similar manner. However, for the original Photomic F meter to be complete there are two accessories, a small pipe which screws into the ring surrounding the meter window, and changes the angle of view to that of a 135mm lens, and an incidence opaque disc attachment which also screws into the surrounding ring and turns the meter into a directional incident meter. To use the original Photomic meter as a reflected light meter, you must turn the ASA dial until the film ASA value is opposite the black arrow, or if using the telephoto attachment, opposite the yellow arrow. To use as an incident light meter, install the opaque disc attachment and stand near the subject, while pointing the meter generally toward the light source.
Fix Old Cameras thanks for the reply. I got my Nikon on auction and awaiting its arrival. Judging from the auction pictures, I don't see those two accessories you mentioned. Are they absolutely necessary?
The meter will function just fine with out them. The tube makes telephoto readings more precise since it is not metering through the lens. The incident attachment is nice for portrait work, but it is not absolutely essential.
I got my old Nikon F today. It's has the prism which has this flag switch to cover the front of the meter. It has no on / off switch. Like this: www.destoutz.ch/accessories_finders_f_photomic_1.html
Stuck a new battery in it and zero response. Really thinking of replicating your video to simply take a peek inside, clean anything that looks dirty. Any suggestions welcome.
Look for a corroded wire coming off the battery contact... a simple fix. With an inexpensive volt meter you can effectively check for battery voltage at key points in the meter system.
While shooting my fourth role of film with my new Nikon F and Photomic FTN finder,, something strange happened to the viewfinder. The shutter speed numbers shown inside the viewfinder somehow got out of sync and no longer match the shutter speed numbers on the outside knob. When I first noticed the problem, the numbers shown inside the viewfinder were half as fast as the numbers on the knob: if the inside reads 4, the outside reads 8. If the inside reads 60, the outside is set to 120. Today, it happened again. Now the numbers on the inside are 1/4 as fast as the outside. It seems to me that somehow a component keeps slipping out of line somewhere inside the viewfinder, but I have no idea how to go about repairing it. Any suggestions?
The link string is slipping on the pulley. Setting the timing is tricky, but can be done. A working unit would help to compare the position.
Hi, could you please explain, if the ring resistor is removed, how is it aligned when replaced back into the housing and where does the wiper contact have to be in relation to it? I have noticed a small notch machined into the ring on the one I have, is this an alignment indicator, witness mark?
Thank you ...and thanks for all the great videos :)
Regards,
Ed.
+Ed Duffner
The mark is relevant to the alignment. Bring the groove on the resistor gear opposite the contact position of the variable brush. Make this adjustment while turning the dial ring while lifted up. If it cannot be made, loosen dial ring set screws and shift the ring to reset. To adjust the ASA scale again loosen the dial ring set screws and line up the position of the ASA number 400 with the index triangle arrow engraved on the dial ring and then set the scale into position.
+Fix Old Cameras
Thak you very much indeed. Great job!!!!
Hey so my meter isn’t working.
With new batteries, the needle shifts about a quarter way to the O.
But when out against a pure white light that would obviously overexpose at iso 800 with the speed set at 1/4s, the needle moves about a quarter way too.
There’s no corrosion on the battery terminals and it indexes correctly. Do you have any idea what’s up with it?
My guess would be faulty power delivery but the question then is how? Or could it be a combo of problems where the check battery needs calibration but also the metering circuit is toast? In the case the the CdS cells are toast, are Nikkormat CdS cells a swap in replacement?
Thanks for the video.
All your suspicions are possibilities. Most likely dirty/faulty resistor rings or faulty CDS cells. You could make the Nikkormat Cells work but they are not a direct swap.
@@FixOldCameras wow thanks lots for the info. You’re super knowledgeable. Let’s hope it’s just a faulty resistance ring
Is this only able to done on an FTn? Is it possible to be done to a Tn finder?
Can someone give me advice, please? I have Praktica LLC which I use very much. But some time ago it fell down and broke its battery contact for exposimeter. When I tried to repair it I found that contact i need to repair is under camera's frame and I didn't find out how to get under that frame.
+Štěpán Lammel
Without a visual reference, and going only from your description it appears that the mirror box will have to be removed to access the area needed to make the repair.
You mention to pay attention to the position of the cathode band, but you don’t say where it should be. I assumed it should be farthest away from the battery, since the current flows from the anode to the cathode. Am I correct in that assumption? Also, if after performing the repair the battery check is completely unresponsive, do you have any suggestions on what to check for troubleshooting? I used the 1N4007 diode.
I figured it out. I should have put the cathode side toward the battery so that the negative side of the diode is facing the negative side of the battery. I will do this over, reversing the orientation of the diode.
Direction of the cathode band depends on the polarity of the system. The IN4007 works very well for the two battery systems. If the battery check is not working check the battery test adjustment resistor and its connectivity.
@@FixOldCameras Good news, reversing the diode worked!
@@TomNorthenscold Right on! Your persistence and patience paid off. Keep'em going.
Nice. What should you glue the leatherette back on with? More importantly, what should you NOT glue the leatherette back on with?
+Hooray for Pentax! Long list of what not to use... Pliobond glue works well as it will hold smoothly and will allow for future removal if necessary. Double sided tape will also work for this application.
+Fix Old Cameras Do you have a preferred version of double-sided tape (3M has numerous versions) and a source to purchase it from?
The 3M 465 tape might be the best choice but it is rather pricey, but a small roll will be enough for many cameras. astore.amazon.com/fixoldcam-20?node=1&page=5
If the leatherette is pliable even a roll of office supply double sided tape will work just fine, however it will not hold leatherette that is stiff and has developed a curve memory.
The aperture linkage on my DP-1 got jammed on a lens mount and now doesn't work properly. it either hangs loosely or hides up into the linkage housing. Do you have a resource you could point me towards?
Take the cover plate off of the linkage and you might find a disconnected spring or lose screw. Also, there is a Fix Old Camera video on the Photomic prism - th-cam.com/video/sy7PbcvCzoE/w-d-xo.html - it might help, but unlikely. Hope to produce video at some point in time isolated to the aperture linkage on a Photomic DP-1 prism.
Fix Old Cameras thanks!
hello, can you repair an exposure meter of my nikon f?
Hello, Just to be clear, the SK 3080 diode works in the two battery Nikon Ftn and the SK 3090 diode works in the two battery Gossen Luna Pro even though the TH-cam for the Luna Pro started out as an SK3080 diode. I bought several of the SK3080 diodes based on the original Gossen TH-cam. ;-(
Frankly, with the difficulty in finding some of the vintage diodes that seem to work the best, an absolute perfect choice might not be available to you. Unfortunately you might just have to give them a try and see how they work. You will not cause any harm to the meter if the diode chosen does not produce the desired voltage drop. The Gossen is fairly forgiving to the voltage difference even though it does not have an in circuit voltage regulating components. The Nikon Ftn is a little more persnickety. Experience shows a silicon diode has a voltage drop of approximately 0.7V(varying 0.1V depending on the sub), while a germanium diode has a voltage drop of approximately 01.6V - 0.2.2V. Making the silicon diode(1N4007) the preferred choice for two battery meter systems. Though germanium diodes(SK3090, OA90, ECG109) with a voltage drop of consistently 016V) is the best in the area of forward voltage drop in single battery systems they are increasingly hard to find and more expensive, the silicon diodes are cheaper and apparently easier to find.
Experience shows a zener diode is not a good choice for a substitute. A silicon or germanium, conducts in one direction only, whereas a zener diode conducts in both directions, but at different voltages.
In most other applications beyond the voltage dropping application an ordinary diode is used to rectify, using its forward bias characteristics, while a zener diode is used to regulate, using its reverse bias characteristics.
If you have a multi-meter with a Diode Test mode you can determine the voltage drop of your diode before installation. The Diode Test mode produces a small voltage between test leads. The multi-meter then displays the voltage drop when the test leads are connected across a diode when forward-biased. The Diode Test procedure is conducted as follows:
If you are checking in circuit make certain no voltage exists at the diode. Voltage may be present in the circuit due to charged capacitors. Other wise, set your multi-meter to the Diode Test mode.It may share a space on the dial with another function. Connect the test leads to the diode. Record the measurement displayed. Reverse the test leads. Record the measurement displayed.
Diode test analysis
A good forward-based silicon diode displays a voltage drop ranging from 0.5 to 0.8 volts for the most commonly used silicon diodes. Some germanium diodes have a voltage drop ranging from 0.2 to 0.3 V. The multi-meter displays OL when a good diode is reverse-biased. The OL reading indicates the diode is functioning as an open switch. The multi-meter will give additional information about the diode. A bad (opened) diode does not allow current to flow in either direction. The multimeter will display OL in both directions when the diode is opened. A shorted diode has the same voltage drop reading (approximately 0.4 V) in both directions.
Substitues for
ECG109 - OA90
1N4007 - DO-41
One more thought, years ago, when the mercury cell was first doomed to extinction along came the "MR-9" battery adapter. Slip a S76 type battery inside the MR-9 and now you have a direct substitute for a MS625 battery. No meter adjustment necessary - the MR-9 had a built -in chip resistor that was supposed to dropt he voltage to 1.35V. Then in maybe 1998 "The New Camera Craftsman" (now out of production along with the original "Camera Craftsman" magazine) ran a short piece on the diode modification. It discussed the technique of connecting a nonlinear component - a germanium diode - in series with the battery as a means of operating cameras that were not necessarily a candidate for the MR-9 adapter. Using a silver oxide button battery as the power source, the resistance of the diode changes according to the amount of the current. With the small current draw of a galvanometer metering system, the germanium diode brings the voltage very close to that of the original mercury cell. In a typical meter circuit of the type indicated, the diode drops approximately 0.157 volts. (1.5v - 0.157v = 1.3443v). Since that short piece appeared in The New Camera Craftsman" and probably before, camera users have continued to report good results of once again having a fairly accurate meter function in the classic cameras that this technique might apply.
@@FixOldCameras I'm not the sharpest knife in the drawer...but here goes, the best option for the Nikon Ftn is the MR-9, and the SK3090 diode for the Luna Pro...right.
@@pauljones7244 The MR-9 is an option that requires no meter modification. But it is important that one be purchased from a reputable supplier. The diode SK3090 install is a good option for the FTN. The SK3090 is hard to locate. The ECG109 is good replacement for the SK3090 also available at phototronic.biz/tips.The two battery system diode 1N4007 is the diode available at phototronic.biz/tips The SK3090 is hard to locate. SK3080 is an incorrect reference in the Gossen video.The Gossen seems to respond well to either diode choice. The FTN will need the ECG109 if you decide to do the diode install.
Any chance you fix FTN finders for hire?
hi, my cds seems to be out of service and original ones are no more available , do you know which modern ones can do the job ?
That is tough one. The photocell resistance (both cells) runs from over 4 Meg in darkness to under 200 ohms in bright light. Its physical size is of course also a consideration when looking for a substitute.
I put GL5516 5-10K photocells, they fit even they aren't encapsulated in a to-18 container ... If it can help
Excellent. Thank you for the update and good to hear of you success.
Hi fine how2, I tried (out of the photomic) with 1n34A - DO 35 Germanium diodes. I checked with a voltmeter... the voltage of brand new silver batteries seems to be 1.59v and with only one diode it falls to 1.49 not 1.35...In fact I think we need 3 diodes in series. Any idea ? Thanks
Under the slight load of the meter the battery output will drop a couple of tenths of voltage and not all diodes are absolutely equal so there is some margin depending on diode used. Try a different diode if you like, you will not harm the meter. Adjustments might need to be made as you proceed.
Thanks
Adding a like diode in series (anode to cathode lead) you will increase the voltage drop. Adding a like diode in parallel (cathode to cathode, anode to anode) you decrease the voltage drop. We need not be concerned with thermal overload due to the low current draw of a classic camera meter circuit. Experimentation with the voltage dropping diodes in a meter circuit will not harm the circuit. If the circuit fails during the process... it had everything to do with the age of the circuit and nothing to due with diode installations. The advantage to the silver battery is that it has very constant voltage over the life of the battery, while the voltage of the alkaline battery drops off, causing errors in readings as the battery ages, but consequently actually has a short period of time when it will deliver the needed voltage of 1.35.
You note the 1N4007 diode. On the video I can’t tell if the first character is a “1” or an “I”. When I search out diodes all I find is a 1N4007. Can you please clarify what that first character is. Thanks, Tom.
1N4007 or SK3080 diodes both will usually work for double 625PX battery meter systems
Fix Old Cameras Great, thanks.
It would be helpful to 1:st get the scope of this video and secondly a valid diode number given. Other than that: thank you!
Vintage diodes are ideal, but the modern substitutes that they cross to are acceptable in most cases . Try a IN34A diode, it should give you satisfactory results.
Nice job, thank you for producing an awesome video. Just ordered a Photomic, since it has such a strange look. I have an old Leicaflex body that I would like to fix. Mirror got stuck in the up position. Do you have a brand of screwdriver to recommend ?
The best you can afford. Starret or Moody are good place to start.
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When things had been designed for being repairable.Progress is relative.
Indeed. Thank you for the comment.
This does not work. By using a diode you loose linearity in the meter. I set these meters for EV9 EV12 EV15.
One thought, years ago, when the mercury cell was first doomed to extinction was... how about some sort of adapter to hold a silver-oxide cell... and then... along came the MR-9. Slip a S76 type battery inside the MR-9 and now you have a direct substitute for a MS625 battery. No meter adjustment necessary - the MR-9 had a built -in chip resistor that dropped the voltage to 1.35V. Then in maybe 1998 "The New Camera Craftsman" (now out of production along with the original "Camera Craftsman" magazine) ran a short piece on the diode modification. It discussed the technique of connecting a nonlinear component - a germanium diode - in series with the battery as a means of operating cameras that were not necessarily a candidate for the MR-9 adapter. Using a silver oxide button battery as the power source, the resistance of the diode changes according to the amount of the current. With the small current draw of a galvanometer metering system, the germanium diode brings the voltage very close to that of the original mercury cell. In a typical meter circuit of the type indicated, the diode drops approximately 0.157 volts. (1.5v - 0.157v = 1.3443v). Since that short piece appeared in The New Camera Craftsman" and probably before, camera users have continued to report good results of once again having a fairly accurate meter function in the classic cameras that this technique might apply.
@@FixOldCameras I have rebuilt well over 500 Nikon FTN meters. If the CDS cells are good there is no problem adjusting the meter for 1.5 volt battery with the top pot. But if the CDS cells are bad the meter will read way to high with 1.5 volt batteries. Diode will lower the reading but you will find the linearity at EV 9 12 15 way out. I have tried numerous diodes and have never had any success in resetting the meters. Sorry but every diode we have tried we have been unable to set at ISO 100 1/125 sec F2 F5.6 F16 and get a balance where low and high reading are accurate. When I rebuilt these meter my tolerance is +-.5 stop.
Also what is VERY important in rebuilding these meters is to remove the old foam to stop the de-silvering of the prism. The foam eats into the silvering of the prism. I replace with new foam. I did 2 Nikon DE-1 prism for the F2 today, the foam in both was powder. I do this in all Nikon meters and prisms. Foam was the worst thing Any camera manufactures used in cameras. This is very true of camera in humid climates.
@@iwctoys1 The degraded foam is relentless in its attack upon the silver coating of the prisms. A gooey mess and one has to wonder if such degradation was known would have the product still been used and to what end the foam's placement served.
@@iwctoys1 Over 500 Nikon FTN meter rebuilds is an impressive number and thank you for outlining your procedure for compensation for the higher voltage of the modern battery.