DIY photo equipment electronics repairs: Basic knowledge is enough for the little that you can do

In my experience, when it comes to electronics in photo devices, you only need a basic understanding to repair it; the rest is for deeper understanding and circuit construction.

There is not much that can be done about electronic problems, but this covers the most common problems:

• contact problems due to oxidation and corrosion,
• defective solder joints and
• defective components (apart from capacitors, rarely observed so far).

So all you need is

• Ohm's and Kirchhoff's laws,
• a basic knowledge of electronic standard components,
• soldering,
• how to use a multimeter,
• rules for safety in handling electronics

This may sound complicated, but it is quite simple and covers analog electronics/camera applications well.




The functionality of this ring resistor for ASA and exposure correction on a Minolta X-700 can be explained using Ohm's law.

Depending on the position of the wiper (not visible here, represented by the yellow bar) over the segmented gold-plated resistance track, more or less current flows and thus the voltage wiper to ground (green arrow) also changes.


Ohm's law shows the relationship between voltage (U), resistance (R) and current (I, German notation):

U = R * I

and rearranging the equation.

Kirchhoff describes current flows and voltages in two laws.

This covers the essentials.

How the camera circuits work remains out of reach anyway, regardless of whether they are analogue or digital.

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I'm looking forward to a discussion on this, because not everyone who deals with photo equipment repairs will see it that way

The multimeter

is primarily used to measure voltage, current and resistance.

In addition to the latter, there is a continuity test, which provides information about whether current is flowing freely or not.


An inexpensive digital multimeter

that measures accurately enough for our purposes is sufficient for these functions. Such devices can be purchased for under EUR/USD 50.





Inexpensive multimeters serve their purpose in DIY photo equipment repairs.


More expensive devices

offer additional functions, may work more precisely after the decimal point, measure very small values and can usually be used to measure large voltages and currents. These do not usually occur in DIY camera repairs with the exception of electronic flash units. Safety for the user and protection of the device also play a role here.



A multimeter in the higher price range is not a must. But if you work with electronics or electrical engineering, it is worth buying.


Multimeters usually have interchangeable measuring tips, except for very simple devices.

Crocodile clips or spring hooks are very useful for attaching the negative lead (COM) to ground. This leaves one hand free when measuring (see picture # 2 above).

The instruction manuals provide information on how to work with the devices and what needs to be taken into account.

An introductory book on electronics is helpful here, for example:

Ronald Quan: Electronics from the Ground Up: Learn by Hacking, Designing, and Inventing

Discover the inner-workings of electronics through innovative hands-on experiments

Are you fascinated by the power of even the smallest electronic device? Electronics from the Ground Up guides you through step-by-step experiments that reveal how electronic circuits function so you can advance your skills and design custom circuits. You’ll work with a range of circuits and signals related to optical emitters and receivers, audio, oscillators, and video.

Click to expand...

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

Ressources








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

If you're new to electronics, it can be difficult to get started.

But if you stick with it and learn the basics, you'll benefit from it in your DIY camera repair projects

I agree that most electrical problems in cameras are caused by basic stuff, corroded wiring, oxidized contacts, etc. But I would avoid making statements like "There is not much that can be done about electronic problems."

This feels like a statement of your own personal limitations rather than hard unknowables. For example, I know I'm more mechanically minded than electrically minded, but just because I don't know how to do something doesn't mean it can't be done. Things like replacing a silicone photo diode or a solenoid with modern off-the-shelf components is possible. I don't have the knowledge to do it, but I'm sure somebody does. I bet somebody could even program a micro to control an electronic shutter if they had the desire. A Pentax ME is a remarkably simple camera once you understand what it's actually doing. I would not at all be surprised if somebody reprogrammed one from scratch. Impressed but not surprised.

The only thing missing in the current environment is motivation. There's no need to resort to these solutions because donor bodies are still plentiful and cheap. If this hobby were more popular and Pentax MEs were selling for $1000, you can bet somebody would start engineering replacement parts. Or if there were just a lot more talented minds doing this stuff, somebody would eventually get interested enough and make it happen. The number of people repairing cameras is tiny compared to other tinkering hobbies like retro computing, for example.

vandergus said:

I agree that most electrical problems in cameras are caused by basic stuff, corroded wiring, oxidized contacts, etc. But I would avoid making statements like "There is not much that can be done about electronic problems."

This feels like a statement of your own personal limitations rather than hard unknowables.

Click to expand...

I have not yet met anyone, either offline or online, who has made more difficult interventions on the electronics of an SLR apart from those mentioned here.

Perhaps someone has been successful in replacing ICs, certainly in replacing the entire flexible circuit board, but other than that?

My highlight so far has been replacing the main LCD on a Canon T90, but that was just delicate soldering work.

I consider replacing a mirror magnet on a T90 to be more of a mechanical task, you have to be skilled as there is not much space. Soldering the two cables on the other hand is easy.

Apart from that, this also includes diagnosing electronic problems, as has been discussed many times. I don't know anyone who does this, unfortunately.

Thanks for the useful information (as always) @Andreas Thaler

I agree with you, even if IN THEORY we could replace any part with "off the shelf" components, it is no that easy. Even skilled professionals may not always be able to do it (some years ago, one refused to fix my T90 as is opinion was that the magnets needed to be replaced by new ones, and he could not source such stuff).

In theory also we could replace the whole circuit with a micro controller, but this needs a very precise understanding of the camera.

In this aspect, mechanical cameras can teach us a lot, as their intricate design of multiple levers, gears and interlocks provide a very precise synchronization of all actions, which would need to be replicated in the programming of a micro controller, if one wants to fix a more "modern" camera.

Disclaimer: I take my fun in (trying to) fixing mechanical issues, rather that more "abstract" fixes. Even fixing a "broken" sporcket on a FTb is an interesting job (in this case, I "just" needed to put a screw back in place. But this needed removing half of the camera inner parts, simply to access two screws holding the QL mechanism. So now the sprocket is ok but I need to resynchronize everything )

We just had a thread on here about a Fuij GA-645Zi repair, which involved a new flex cable that was reverse engineered.


This guy ordered new CdS cells for his Minolta SRT


This person figured out how to drive a galvonometer using an arduino and a light sensor


And this dude completely reverse engineered the electronics in a Pentax Electro Spotmatic!


Lot's of stuff is possible.

vandergus said:

We just had a thread on here about a Fuij GA-645Zi repair, which involved a new flex cable that was reverse engineered.

Fuji GA-645Zi Repair: In Praise Of Fototech

I have a Fuij GA-645Zi that is well over 20 years old. Like so may of these cameras, mine had the dreaded "dead LCD display" problem. The issue is that Fuji used a flex printed circuit board to go from the camera body into the back cover where the LCD lives. Over several decades, that flex...

www.photrio.com

This guy ordered new CdS cells for his Minolta SRT

Minolta SRT CdS cell - looking for NEW

Hi all! Does anyone know where to find NEW CdS cells for a Minolta SRT? I have about 3 cameras that are declining in sensitivity and linearity, so the meters can no longer be calibrated across the full range of EVs. I have verified with 2 techs and other electronics sources that old CdS cells...

www.photrio.com

This person figured out how to drive a galvonometer using an arduino and a light sensor

Rolleiflex 2.8F Light Meter Upgrade [Part #1]

berg.land

And this dude completely reverse engineered the electronics in a Pentax Electro Spotmatic!


Lot's of stuff is possible.

Click to expand...

That's interesting, and in some ways impressive, but it doesn't help with practical repairs.

For example, a Minolta X-700 with an electronics problem that has nothing to do with the power supply and capacitors quickly runs out of ideas.

Perhaps you can still repair an electronic flash unit from that era with its discrete standard components, as long as an IC isn't broken (spare parts) and the associated circuit diagram is usable.

It's fortunate that the electronics design of such cameras is well thought out and the devices work for decades.

The most common causes of problems remain the power supply and broken capacitors, which can usually be fixed.

Laurent said:

In this aspect, mechanical cameras can teach us a lot, as their intricate design of multiple levers, gears and interlocks provide a very precise synchronization of all actions, which would need to be replicated in the programming of a micro controller, if one wants to fix a more "modern" camera.

Click to expand...

I consider the mechanics in SLRs, especially those from their heyday in the 1970s, to be at least as sophisticated as the later electronics that took over many tasks.

These mechanical precision switchgears first have to be designed, calculated and made to work. These are fantastic engineering achievements.

Andreas Thaler said:

I consider the mechanics in SLRs, especially those from their heyday in the 1970s, to be at least as sophisticated as the later electronics that took over many tasks.

These mechanical precision switchgears first have to be designed, calculated and made to work. These are fantastic engineering achievements.

Click to expand...

I agree, these mechanical wonders do the same as electronics did some years later.

At the moment I have to admit I'm in love with the Canon EF, which makes even the F1 look like an inferior design in many aspects... But the beauty of the FTb inner parts is something to marvel at.

And I can't even imagine what it takes to DESIGN such things...

Andreas Thaler said:

I consider the mechanics in SLRs, especially those from their heyday in the 1970s, to be at least as sophisticated as the later electronics that took over many tasks.

These mechanical precision switchgears first have to be designed, calculated and made to work. These are fantastic engineering achievements.

Click to expand...

It's indeed humbling to study some cameras from the 1950s and 60s and realize that their designers had developed a form of programmed-mode automation using nothing more than a selenium PV cell, a galvanometer, and precision mechanisms: No batteries, no integrated circuits, and certainly no microcontrollers!