Nikon FG: A closer look at service and technology

[Andreas Thaler]

File:NikonFGblkfrt50f18.jpg - Wikimedia Commons

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The Nikon FG, produced from 1982 to 1986, continues our series on servicing electromechanical SLRs.

The FG was the successor to the Nikon EM camera of 1979 and the predecessor of the Nikon FG-20 of 1984. These three cameras composed Nikon's first family of ultra compact 35mm SLR camera bodies. Although the FG had a much less advanced shutter than the more expensive Nikons of the day, it had a very sophisticated electronic design compared to earlier electromechanical Nikons.

Features:

• First Nikon SLR with programmed auto-exposure (AE).
• First Nikon SLR with TTL (through the lens) flash exposure control from a standard ISO-type hot shoe.
• Electronically controlled focal plane shutter.
• Exposure compensation dial (−2 EV to +2 EV).
• Audio warning system – advises of under or over exposure.
• Back-up mechanical M90 and bulb shutter settings enable the use of the camera when batteries are drained.

Nikon FG on Wikipedia

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The Nikon FG is a small, compact SLR with a die-cast body and plastic exterior.

It has a distinctive shutter release sound that sounds like a soft, lingering echo. I’ve always wanted to know how that happens.

Agenda

• We’ll open up a working Nikon FG, examine the electronics on the top board, remove the mirror box, and perform a complete CLA (clean, lube, adjust).
• This also includes advanced DIY tasks such as measuring the flange focal distance with a depth gauge, adjusting a Nikkor lens with the autocollimator, and, based on that, testing the rangefinder system.
• Furthermore, we will examine our Nikon FG with the camera tester and check the curtain travel times and the EE error (exposure error of the exposure metering system).
• We’ll look at where and how the FG’s electronics can be adjusted.
• We’ll also examine the materials used in the mechanics and how they’ve held up over the decades.
• If anything needs repairing, additional FGs are available as parts donors.
• A test color film that we’ll shoot and scan during a walk through downtown Vienna will serve to evaluate the success of our CLA.

All of my work is based on the available professional technical and user documentation for the Nikon FG and the experience I have gained so far working on electromechanical SLRs:

• Nikon FG Service Manual
• Nikon FG in SPT Journal
• C & C Nikon FG Electronics Troubleshooting Guide
• Nikon FG Instruction Manual

Information on Nikon FG service and preparation

There is already an excellent service report on the Nikon FG by Richard Haw, who is also known for his work on Nikkor lenses. It provides insights into the inner workings of the SLR, technical information, and instructions for a partial disassembly.

We will take an even closer look inside the FG and remove the mirror box. This is necessary to check the condition of the mechanical lubrication and to work on the shutter. We will also examine the mechanisms for film transport and shutter cocking.

I’m following the instructions in the SPT Journal for the Nikon FG; see sources above.

I’ve listed here what I generally consider important to keep in mind during a CLA.

Technical documentation

For servicing and repairing the Nikon FG, I’ve reviewed the Nikon FG Repair Manual (243 pages), the SPT Journal (16 pages on the FG by Master Larry Lyells), and the C & C Associates Troubleshooting Guide for the Nikon FG (22 pages).

The FG is thus exceptionally well-documented technically; all the information needed for a CLA and troubleshooting is provided in full.

Complexity

Don’t be fooled by the size of the Nikon FG or its positioning as an amateur camera. It is a complex electromechanical SLR with microprocessor control that processes analog and digital electronic signals.

Removing the front plate with the mirror box is correspondingly involved, comprising 34 steps. Cables must be desoldered, parts removed, and screws loosened. All in a specific order.

Disassembling these SLRs haphazardly almost always leads to failure, as the dense layout with flexible circuit boards and connections makes it unclear how to proceed safely.

Project documentation

I will document this project—and all subsequent ones—step by step with text and photos.

Anyone using these documentations for their own work should definitely study the technical documents listed and follow them as a priority. They are the original sources for all work.

Requirements

Performing service and repairs on electromechanical SLRs requires a minimum level of repair experience as well as basic knowledge of precision mechanics and electronics. You can acquire the necessary knowledge and skills on your own; excellent specialist literature is available. Courses in analog and digital electronics can support this. Important skills include interest, a willingness to learn, patience, perseverance, and resilience, and, of course, a steady hand. Knowledge and skills in soldering are important for all electronic SLRs.

No shortcuts

I'd like to emphasize that there are no shortcuts to service and repair. Electromechanical SLRs almost always require more or less thorough disassembly in order to clean, lubricate/oil, and adjust it. This also applies to troubleshooting. The mentioned technical documents provide all the necessary instructions.

Without these instructions, I consider any attempts at service and repair pointless, as these SLRs must be disassembled in a specific sequence.

A basic set of tools, equipment and materials is required to carry out the work. A digital multimeter and an oscilloscope are required for electronic measurements.

Practice

Before you start working on the SLR you're repairing, you should practice all the procedures on a decommissioned one. This will help you learn how the camera is constructed and gain valuable experience. Mistakes don't matter; you'll always end up with valuable spare parts.

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A word of caution

Please keep in mind that you’ll be using highly flammable solvents for service work, and their fumes are harmful to your health. Soldering also produces fumes that should not be inhaled. Dangerous high voltages can be present when handling electronics, especially in conjunction with electronic flash units and mains. Therefore, familiarize yourself with the safety regulations beforehand and ensure your safety. Depending on the activity, protective gear may be advisable.

All information provided without guarantee and use at your own risk.

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That was a rather dry introduction

To make up for it, here’s the Nikon FG sales brochure available for download in PDF format.

For the full project report see on photo.net:

Nikon FG: A closer look at service and technology

 

[ic-racer]

Nice write up.

A couple things I do different with the collimator.
I have a front surface mirror that I set on the base. This allows me to reflect the infinity image upward so I can view it with the camera and don’t have to twist the unit to view the infinity image.

Also, when the cameras mirror is down, the collimator can image focusing screen, if you know which depth of the focusing screen on which to focus the collimator , this can also provide a good test of the cameras focus screen.

 

[Andreas Thaler]

Nice write up.

A couple things I do different with the collimator.
I have a front surface mirror that I set on the base. This allows me to reflect the infinity image upward so I can view it with the camera and don’t have to twist the unit to view the infinity image.

Also, when the cameras mirror is down, the collimator can image focusing screen, if you know which depth of the focusing screen on which to focus the collimator , this can also provide a good test of the cameras focus screen.

Thank you!

I'll be posting my own articles on the autocollimator soon (they're already finished). I'd appreciate it if you could explain the method for verifying the rangefinding system in more detail there.

 

[ic-racer]

I’ve had my Autocollimator for a few years now and I’ve done quite a lot of experimentation with it.

For example, indeed, it’s best to set the best plane of focus on the film rather than at the level of the rear rails or the front most rails.

However, check this out, if you go through a 24 exposure role of film, the film sits in a different position at each frame!

Therefore, another way to do it is to use the Autocollimator to check the pressure plate, which is essentially the rear set of rails, and then subtract from that a nominal distance, which would be where the film should sit.

Film Flatness Test

I just got a camera with 1/2 roll of expired film. I removed the film from the camera and put it in a Rolleiflex SL35 to test frame-by-frame flim flatness. This Rolleiflex SL35 was set to focus 0.15mm in front of the pressure plate. With in mind, I used an Autocollimator to measure the front...

www.photrio.com

 

[Andreas Thaler]

Post note:

SLRs like the Nikon FG, as well as other electromechanical (hybrid) SLRs, are considered too complex and thus unsuitable for DIY servicing or repair.

This is because tinkering and winging it won’t get you very far here. These cameras are simply too intricately designed.

It’s not clear how to disassemble them on a whim all the way down to the shutter. Flexible circuit boards, inaccessible wired components, and interlocking couplings make non-destructive disassembly and safe reassembly nearly impossible.

This reality is often dismissed with the claim that „electronics“ simply cannot be repaired or that flexible circuit boards have a lifespan of around 15 years, as I recently learned on Reddit (…)

And so, one sees very few service or repair reports, if any at all.

This FG was the first one I had taken apart and reassembled intact.

I didn’t succeed because of any special skills or talents, but by consistently following the instructions in the technical documentation (SPT Journal).

For almost all of these SLRs, these keys are readily available; you just have to be willing to put in the effort. But few, if any, make this visible. It doesn’t have to be that way.

I deeply regret that people interested in DIY seem hesitant to get involved in this field. And I won’t rest until that changes

Here's a suggestion to get you started; it's doable:

How-to guide DIY service/repair for electromechanical SLRs: How do I get started with DIY? (part 1/8)

Over the past few months, I’ve been active online with the goal of making DIY service/repairs for electromechanical SLRs accessible to a wider audience. The aim is to help preserve these beautiful and ingeniously designed SLRs from Japan dating from the 1970s and 1980s. This is because repair...

www.photrio.com

Don't let these wonderful electromechanical SLRs go to waste. It's easier than you think,

says the missionary from Vienna