Little information about repairing electronic cameras

[Andreas Thaler]

I wonder why there is almost no information about repairing the electronics of SLR cameras.

I'm thinking of cameras from the late 1970s to the mid-1980s, whose electronics are not yet that highly integrated.

Electronic faults can generally be analyzed, components can be removed from abandoned copies and replaced. This also works with other electronic devices of this time.

Anyway I can find very little about it on the web/technical literature.

What do you think is the reason for this?

Is it perhaps because the electronics of cameras are so tightly installed and connected to mechanical parts, making access more difficult than, for example, a stereo system?

Or are electronic topics generally unpopular and considered too complicated?

 

[wiltw]

The electronic circuits in many SLRs consists of multi-layered connections using 'flexible circuits'. The removial of components mounted on such circuits is made more difficult due to what are called 'thru-connection holes' for the circuit components, particlarly if the component itself is a multi-pin component. So repair is a more modular replacement of an entire flex circuit rather than replacement of a failed component. Therefore the need for schematics for the circuits is obviated by the difficulty of replacement of components...it is far easier to isolate problems to 'need to replace circuit X'..

 

[koraks]

The electronic circuits in many SLRs consists of multi-layered connections in flexible circuits.

Yeah, but:

I'm thinking of cameras from the late 1970s to the mid-1980s, whose electronics are not yet that highly integrated.

So no difficult and highly integrated flex pcb's, and components etc. Btw, such stuff isn't all that hard to work on if you have the right tools, and those tools these days are fairly cheap and easy to get. The problem with the more modern stuff is that you're dealing with microcontrollers and asics, so even if you have a schematic (which you generally won't have for a typical EOS etc), you still don't know what logic goes on under the hood of the uC's etc.

With 60s, 70s-early and 80s cameras, the odds of having some kind of schematic are a little better and the electronics are generally straightforward. The most error prone things tend to be old CdS cells or electrolytics that have died, or small electromechanical components that have gone out of adjustment etc. I guess that sort of stuff is relatively easily taken in stride along with the mechanical work and therefore probably has never been discussed separately very much.

 

[Andreas Thaler]

In addition to wiltw:

The flexible print circuit (FPC) of the Minolta X-700 eg. is a challenge when it comes to replacing the entire board or the five ICs.

Two of the ICs are folded into the FPC like in a sandwich and can only be accessed after numerous cables have been unsoldered. All electronic parts there are small and fragile.

Desoldering is difficult because the soldering pads are quickly removed. When soldering, the non-flat FPC is a handicap to align the 64 IC pins.

I think the service people replaced the entire unit back then and didn't troubleshoot to save time. Even if the service manual describes errors and possible solutions.

And who thought it possible 40 years ago that fools like me would try to patch the electronics of this camera

 

[Andreas Thaler]

With 60s, 70s-early and 80s cameras, the odds of having some kind of schematic are a little better and the electronics are generally straightforward.

In the service manuals, eg. for the Canon AE-1 or A1, the circuits are described in detail, in addition to the block diagram, circuit diagram and layout. You can still learn something there.

 

[BrianShaw]

Service people replaced parts at the LRU level (line replaceable unit) because that’s how the device was designed to be maintained/repaired. Those LRUs are specified in the repair manual parts list.

The lower level repair that you are doing is much more specialized than a normal “field repair”. In some communities that would be called a “depot repair” with the depot being a specialized facility with specialty-trained specialized repair people.

@wiltw made this point above using slightly different words.

 

[Andreas Thaler]

So repair is a more modular replacement of an entire flex circuit rather than replacement of a failed component.

Which requires more skill than technical understanding

 

[koraks]

In the service manuals, eg. for the Canon AE-1 or A1, the circuits are described in detail, in addition to the block diagram, circuit diagram and layout. You can still learn something there.

Exactly. Very little hope for something like that in a T50-T90 or EOS series camera! Those diagrams of course do exist, but they're pretty darn big and I think Canon et al. have done their very best to prevent them from floating around the internet.

 

[Andreas Thaler]

Service people replaced parts at the LRU level (line replaceable unit) because that’s how the device was designed to be maintained/repaired. Those LRUs are specified in the repair manual parts list.

The lower level repair that you are doing is much more specialized than a normal “field repair”. In some communities that would be called a “depot repair” with the depot being a specialized facility with specialty-trained specialized repair people.

@wiltw made this point above using slightly different words.

That's interesting, thank you for the explanation.

That would mean that components were more likely to be replaced in the independent workshops?

 

[Andreas Thaler]

Exactly. Very little hope for something like that in a T50-T90 or EOS series camera! Those diagrams of course do exist, but they're pretty darn big and I think Canon et al. have done their very best to prevent them from floating around the internet.

It irritates me that no one understands in detail what is going on in these circuits

The circuits in the IC are usually only roughly documented, which is clear when there are thousands of components.

In any case, a brilliant achievement by the engineers back then.

 

[koraks]

The circuits in the IC are usually only roughly documented, which is clear when there are thousands of components.

Yes, and as said, they're usually microcontrollers, so even if you knew the hardware circuits, you'd still have to also know the code to figure out what they do exactly. Since you're then facing the task of making your way through many thousands of lines of assembler code, it's no fun even if you manage to get the listings.

In any case, a brilliant achievement by the engineers back then.

Ain't that right! I realized this when I looked into the aperture mechanism on EF lenses. They figured out a reliable way back in the 1980s to communicate between a body and a lens, and to embed sufficient intelligence in the lens to accept simple commands along the lines of 'run aperture motor clockwise for x microseconds'. Not only this - the stuff they made back then for the most part still works flawlessly today. And that's just one tiny subsystem...it's really amazing.

 

[BrianShaw]

That's interesting, thank you for the explanation.

That would mean that components were more likely to be replaced in the independent workshops?

If you are thinking of piece parts on the LRU, then I seriously doubt it. I'd asume that repair shops follow the published manufacturer's repair guides. That has been my experience at both independent repair shops as well as manufacturer repair (or authorized repair). Let's face it... camera repair people are skilled but they are not engineers. The supply chain on the LRUs is why many cameras are "unrepairable"... they simply aren't being supplied anymore.

"Depot level repairs" are generally limited to very specialized equipment that are worth lots of $$$ (or whatever unit of currency you use), oftehn military equipment where money is object.

 

[Chan Tran]

I wonder why there is almost no information about repairing the electronics of SLR cameras.

I'm thinking of cameras from the late 1970s to the mid-1980s, whose electronics are not yet that highly integrated.

Electronic faults can generally be analyzed, components can be removed from abandoned copies and replaced. This also works with other electronic devices of this time.

Anyway I can find very little about it on the web/technical literature.

What do you think is the reason for this?

Is it perhaps because the electronics of cameras are so tightly installed and connected to mechanical parts, making access more difficult than, for example, a stereo system?

Or are electronic topics generally unpopular and considered too complicated?

While with schematic diagram I can understand and probably diagnose what is wrong with an electronic camera but unlike a stereo system I wouldn't dare to disassemble a camera or to replace a component. Also many of the IC used in cameras are custom made and not standard like in a stereo system.

 

[Andreas Thaler]

In addition to the manufacturer's service manuals, I can recommend the SPT Journal & Service Notes, the editions of The Camera Craftsman and the C & C Electronic Troubleshooting Guides.

Larry Lyells, technical director of The Camera Craftsman, wrote excellent articles on the electronics of various cameras from the 70s to 90s. Often the key to making progress with repairs.

 

[BrianShaw]

It irritates me that no one understands in detail what is going on in these circuits

The circuits in the IC are usually only roughly documented, which is clear when there are thousands of components.

In any case, a brilliant achievement by the engineers back then.

Somewhere in the world, at some point in time, there was/is the documentation that you seek. It is called the detailed product specification(s). Each engineered component, part, and assembly had associated engineering documentation. That is used to engineer, cost, procure parts, and manufacture the product. It is generally not available for commercial product repair activities. That kind of material is generally internal and kept at close-hold; It's the "secret sauce" and proprietary. I've never, personally, seen that level of documentation leaked to the internet. It's difficult enough to get the manufacturer's service/repair manuals.

I agree that engineereing is a brilliant achievement. In a situation like you are engaged, reverse engineering also is a billiant achievement!

 

[Andreas Thaler]

While with schematic diagram I can understand and probably diagnose what is wrong with an electronic camera but unlike a stereo system I wouldn't dare to disassemble a camera or to replace a component. Also many of the IC used in cameras are custom made and not standard like in a stereo system.

I agree.

One complication with camera electronics is that they cannot be separated from the mechanical components for practical testing. Therefore everything has to be done in-camera and that means lots of pitfalls when partially dismantling.

 

[Andreas Thaler]

That kind of material is generally internal and kept at close-hold; It's the "secret sauce" and proprietary. I've never, personally, seen that level of documentation leaked to the internet. It's difficult enough to get the manufacturer's service/repair manuals.

It is to be feared that these documents were disposed of together with spare parts that were no longer manufactured.

 

[BrianShaw]

In most cases, it is not unreasonable to consider a camera to be disposable when "normal repair" cannot be economically performed. The biggest cost is labor and that very quickly exceeds the value of the camera or the cost of replacement with another working unit. But if the detailed level of repair is for hobby and to succeed at a huge challenge... then all is good.

 

[BrianShaw]

It is to be feared that these documents were disposed of together with spare parts that were no longer manufactured.

Yep... highly likely. Or just lost over time. To the manufacturers, that documention has little value after the product ceases to be made/maintained by them. The cost of archiving for potential future reference is high enough that it is dobtful to have ever happened.

 

[Andreas Thaler]

But if the detailed level of repair is for hobby and to succeed at a huge challenge... then all is good.

The camera corpses are already piling up here

 

[Dan Daniel]

I worked for a repair tech who was very knowledgeable about these kinds of circuits. He had started in the '70s so pretty much 'grew up' on the kind of cameras you are looking at. From what I saw of his work, he would go into old circuitry if the solution was simple. He could troubleshoot bad capacitors, pots, etc. And if the circuit allows for simple repairs, he could do them, Swap out components from donor bodies. Jump around bad continuity, etc. But the bar was low- simple or it was either a plug and play/pray of a whole circuit or tell the customer that the camera was unrepairable. I don't think he was really tracing circuits out. Just grabbing the obvious issues if need be, using factory manual troubleshooting keys, etc. And most of those factory manuals will, as people have been saying, often end with 'if a, install new X, thank you good bye.

And this was someone who did understand these circuits and knew how to deal with multilayer boards, etc. As people have been saying, you may be expecting more detailed repair work than was the norm in the past.

On the documentation front, I remember that he had a disk full full full of factory camera manuals. So the material has been digitized (well, jpegs of manual pages, not true digital searchable documents). You should keep asking old repair techs how to get your hands on this library. I imagine lots of hard disks have been sent to the dump already holding this stuff.

 

[ic-racer]

A while back I got some NOS circuit boards to repair some Rollei SL35E cameras. However, the 'new' circuit boards showed some of the same failures in the metering circuity as the cameras.

To troubleshoot the boards, the underside would need to be visible, yet, they would need to be hooked up to all the potentiometers and switches in the camera body.

I was able to repair the mechanical shutter on all the cameras, however. So, they could be used with an external meter.

 

[wiltw]

The older the gear, the more reliance on mechanical components and analog circuits; the analog voltages and resistances, etc. could be read by the tech and the out-of-spec part replaced.
Get into more recent gear, and we get into the world of Logic circuits... "If Pin A is Hi, and [Pin B is Low or Pin C is Hi] then set Pin D to Hi" (and Pin D lights up an LED indicator in the viewfinder). And there would be a big chart (in the Engineering offices only) that documented the many different logic patterns that were built into the design. Interesting to see a bit of the hi-lo logic states depicted within the schematic of that (Rollei 35) wherein the logic in the mid-1960s was simple enough to include for diagnostic purposes.
And in even more recent designs, the manufacturer has the means to upload new firmware into the logic, rather than the logic being 'burned in' permanently, so publishing any chart is obsoleted by any firmward update.

 

[Chan Tran]

Another problem is that camera manufacturers do not let anyone like us access their software tools used to calibrate these cameras. I know that Nikon has the software which they could adjust the shutter and exposure meter on the F5 without disassembly. They no longer service the camera and thus they no longer use the tools but they wouldn't let anyone have or buy these software.

 

[Andreas Thaler]

A big thanks to everybody who has contributed to this thread so far

+++

For my part, I was lucky today and was able to resurrect a mint Minolta X-700.

Capacitor C9 (electrolytic capacitor) in the top deck was leaking and was losing electrolyte, being still liquid but had not caused corrosion on the board yet.

As a precaution, I also replaced the second electrolytic capacitor (C10 in the bottom of the camera), whose values were still ok, but had already exceeded its age limit.

The symptoms were the familiar ones: LEDs in the viewfinder went out as soon as the shutter button was pressed, and the shutter did not fire. But that can also have other causes and then it will be a long day

The key for me to higher repair success would be to replace the ICs if necessary. I practice this on abandoned X-700.