Troubleshooting electronic SLRs: There is little you can do, but do it

I wonder what options there are to find and resolve errors in a highly integrated electronic camera circuit.


For example, the Minolta X-700

five ICs, several discrete electronic components and electromechanical parts.



Under the hood of the Minolta X-700


It is of course possible to go in here with a multimeter, an oscilloscope or a digital logic probe and measure electronic values.

But what sense does it make?

Where the function of the respective circuit section is clear, this can provide information.

For example, when it comes to the power supply, whether the plus and ground cables supply the circuit, i.e. whether the operating voltage can be measured at the connections on the board.


But from then on it becomes difficult or impossible

The voltage that the ICs output at their pins is no longer directly comprehensible according to the statement „the current runs from A via B to C“.

The ICs contain highly complex circuits that are not documented in detail and work mostly digitally. So with voltage levels HIGH and LOW. Either there is voltage or there is not. Whether this is good or bad is not obvious. It depends on the circuitry in the IC.

What you can do is compare the voltage values on the individual pins with the reference in the service manual, if there are any.



IC pin voltages of the Minolta X-700


But that also says little to nothing. All that can be said is that with action X, reaction Y does not occur. Why, where in the IC - that remains hidden. Then the only thing left is to assume that the IC is defective.

You can also check components such as electrolytic capacitors and tantalum capacitors as „the usual suspects“ and replace them if necessary. Check cables, conductor tracks, switches, solder connections, but they are unlikely to break on their own. Unless moisture got into the camera, leaked battery acid ate it away or the camera fell on the floor.

But otherwise?


The trouble shooting tables in the service manual are used here.

Error patterns, their possible causes and possible solutions are given as decision diagrams.



Excerpt from the service manual for the Minolta X-700


You can test yourself here. And if you're lucky, you'll find the error.

Then you have to fix it.

That means dismantling, unsoldering the cables, keeping track and doing the whole thing backwards.

And it needs spare parts - from other cameras.

There is always the risk of causing further damage when working on a complex camera.

And these diagrams do not explain how the circuit actually works. Given the tens of thousands of transistors in ICs, it wouldn't even be possible.


Help from specialist magazines

Explanations of the electronic circuits of various SLR models and troubleshooting instructions can be found in these publications. If you are interested in repairing electronic SLRs, you should definitely look for these:

• The Camera Craftsman
• SPT Journal & Service Notes
• C & C Electronic Troubleshooting Guides
• Camera Repair Manuals by Larry Lyells

Service manuals by manufacturers

Containing circuit diagrams, layouts, exploded views, parts lists, reference values, troubleshooting guidance and (sometimes) detailed explanations, how circuits work:









Conclusion

• There's little you can do - and you spend a lot of time with such sick cameras.
• Nevertheless, you should leave no stone unturned.
• Sometimes you get lucky, or it's actually just the battery that's inserted the wrong way around

+++

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

Some more links added to sources for service manuals.

There are certainly others, but I know these sources from my own experience.

That's great, but one basic question would be -- How to turn the electronic camera ON, even when I have what I THINK is a NEW GOOD battery?

Answer? Try a different brand or type of battery. Turn the camera OFF & ON several times. Remove the batteries, check the contacts, try again. ETC.

The camera might be fine. The problem might be getting "the juice to the goose".

I guess if it's a broken wire or soldered connection, transistor, resister, capacitor or diode , a repair can be made. If it is the integrated circuit need a doner body. Not sure how long with take to trouble shoot the system.

Example of a (failed) troubleshooting using my approach

Minolta X-700: Electronics fault > spare parts box


An X-700 whose LEDs in the viewfinder do not light up and which does not trigger.

I start by troubleshooting electrolytic condensator C10 in the camera base:

• Unsoldering the electrolytic capacitor, measuring the capacity with the multimeter - ok.
• Solder in

Look at the circuit board on which the electrolytic capacitor sits:

• A conductor track is broken and I'm bridging it. A second X-700 that works acts as a reference.
• The circuit board looks worn out, I finally decide to replace it. Replacement comes from an abandoned X-700.
• Some soldering work as several cables run from the camera to the circuit board. Unfortunately there is no change in the status, the camera remains dead.

Replacing the circuit board in the camera base does not resolve the problem.


I look at electrolytic condensator C9 in the upper deck:

• It has obviously already been replaced, the soldering is quite tough
• I unsolder the electrolytic capacitor, measure it and connect it to the camera using two extension cables. This way I can test whether there is a change without having to do the delicate installation work.
• Unfortunately no
• Even an open ground cable that I soldered on on suspicion doesn't decide the match for me.

In the service manual, this error pattern only refers to the power supply.

• There is voltage on the electrolytic capacitors and on the small circuit board where C10 is located.
• The solder joints and components on the flexible circuit board above the prism show no abnormalities.
• What I can see, I have seen. The rest of the circuitry is hidden in the five ICs, in the housing and in the sandwich of the flexible board, which I leave as it is.
• Maybe the previous owner shot one or more ICs due to static electricity - I don't know.
• A red dot on the housing and into the spare parts box.

---

Conclusion

• Finding electronic faults in highly integrated circuits is a game of bad cards.
• Even if an IC is identified as faulty, it must be unsoldered and a replacement soldered in. With five ICs, only two of which are accessible, and four of which have 64 tiny pins each, the chances are slim.
• In order to be able to see the circuit completely, it must be dismantled. On the X-700, the flexible circuit board is also folded as a sandwich. This also means that all connections to the periphery are lost. The success of a repair measure cannot therefore be tested directly.
• This means that troubleshooting is mainly limited to the usual suspects, i.e. errors in the power supply and defective electrolytic capacitors. There are several tantalum capacitors in the X-700, as well as lots of cables running through the camera.
• That's why it's smart to be modest when it comes to repair

Flexible circuit board over the prism, folded as a sandwich.

This includes, among other things two more ICs.


+++

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

How long did it take you to get as far as you did? If the IC board is bad, replace with a donor body, same age, what are chances the donor card will go bad soon after replacement?

Paul Howell said:

How long did it take you to get as far as you did? If the IC board is bad, replace with a donor body, same age, what are chances the donor card will go bad soon after replacement?

Click to expand...

All in all it will have taken around two hours.

It would be possible to replace the entire electronics. This is the folded flexible circuit board with numerous cable connections. For this I would have to use a defective X-700, whose electronics are intact, as a donor. I have nothing there. The work is extensive, but can be done with instructions.

If I could manage to identify one of the ICs as defective, it would be difficult for me. I was able to unsolder the small components with 64 pins in the experiment, but not to solder them in, at least not with perfectly soldered pins. In addition, the board is not flat where the ICs are located, which is a complication when soldering.

IC 3 and 4 are in the circuit board sandwich. To get to them I would have to at least partially dismantle the circuit board. Without knowing for sure that they are the cause of the problem, although in the C & C Troubleshooting Guide to the X-700 there are test procedures for the two that are made on the top of the board.

So that was the end of it for me.

I think that these boards were intended for complete replacement rather than repairs.

But maybe I'll try it again, there are still candidates for repairs here.

If the replacement was successful, I don't see an expiration date for the board.

You probably need to learn a couple of techniques for ICs using surface mount methods: desoldering/resoldering with a temperature-controlled heat gun (where appropriate), and/or using a temperature-controlled soldering iron with a broad bit to solder all the pins down one edge at the same time. You prep the solder surface with solder or solder paste, pop the IC roughly into place, and rely on surface tension to pull it into alignment when heat is applied. Use a low-temperature solder; if possible a solder designed for flexiboards. Low-temperature solder is also good for desoldering stuff. Also, heat-controlled tools to melt the solder at the correct temperature, without damaging the flexiboard. There are plenty of guides out there. (Low temp solder has its own issues, but the melting temperature of 1970's solder is perilously close to the melting/delaminating temp of flexiboard, so it's good to mix the low-temp stuff in during the desoldering process.)

Other relatively cheap tools that can be very useful: voltage injectors (often a bit of wire), signal injectors, cheap oscilloscope so you can look at signals, some way of identifying hotspots: alcohol is often used for this, but it can be hard to pinpoint exactly what is overheating. A dusting of flux powder can help pinpoint down to part of a component. Again, there are plenty of guides out there. You'd be surprised how few pins you're actually interested in on an IC: most of them are working just fine and are waiting for a signal from somewhere. Typically, you inject a signal on one pin, and expect a result on a different pin. If it's OK, you work backwards (usually) to find the break in the chain.

Bushcat said:

You probably need to learn a couple of techniques for ICs using surface mount methods: desoldering/resoldering with a temperature-controlled heat gun (where appropriate), and/or using a temperature-controlled soldering iron with a broad bit to solder all the pins down one edge at the same time. You prep the solder surface with solder or solder paste, pop the IC roughly into place, and rely on surface tension to pull it into alignment when heat is applied. Use a low-temperature solder; if possible a solder designed for flexiboards. Low-temperature solder is also good for desoldering stuff. Also, heat-controlled tools to melt the solder at the correct temperature, without damaging the flexiboard. There are plenty of guides out there. (Low temp solder has its own issues, but the melting temperature of 1970's solder is perilously close to the melting/delaminating temp of flexiboard, so it's good to mix the low-temp stuff in during the desoldering process.)

Other relatively cheap tools that can be very useful: voltage injectors (often a bit of wire), signal injectors, cheap oscilloscope so you can look at signals, some way of identifying hotspots: alcohol is often used for this, but it can be hard to pinpoint exactly what is overheating. A dusting of flux powder can help pinpoint down to part of a component. Again, there are plenty of guides out there. You'd be surprised how few pins you're actually interested in on an IC: most of them are working just fine and are waiting for a signal from somewhere. Typically, you inject a signal on one pin, and expect a result on a different pin. If it's OK, you work backwards (usually) to find the break in the chain.

Click to expand...

Thanks for pointing on this.

The necessary tools for SMD work are available here and also some practice.

As already mentioned, soldering on this uneven board with very narrow pin spacing and easily coming off conductor strips is tricky. Even if I can swap the two directly accessible ICs on the top, I would have to completely dismantle the board for the other two, which is a lot of work with corresponding risks. In addition, determining the error is anything but easy. As far as I can tell, there are three sources of troubleshooting instructions for the X-700. If these work, you're lucky, if not, you're in the dark. Ultimately, you have to weigh up whether you want to invest time and work or whether it would be better to replace the electronics straight away.

But I would like to turn it into a project that we can work on together here.

There are still a few X cameras here that should have errors. It would be enough to do some electronic troubleshooting on an X-300 or X-500. Although they have fewer ICs, their structure is comparable.

We could go through troubleshooting, desoldering ICs and soldering them in, right on their original boards.

How do you think about this?

Last winter I went down the rabbit hole of circuit board swapping. It took about 4 hours to swap out a circuit board each time for trial and error. What I needed to make is a camera body with about 16 jumpers on alligator clips that can be connected relatively rapidly to a board for testing.

In terms of why the 'bad' circuit boards were 'bad' my impression was the resistors, capacitors or sloder joints were bad, rather than the ICs. That conclusion came from the fact that some IC based functions still worked yet others did not. The thought being if an IC failed, all its functions would also cease.

Also, these Rollieflex SL35E cameras and circuit boards were made at their Singapore facility that, at the time, had quality issues. I have given up on the SL35E electrical repair project but I suspect Nikon and Minolta cameras that you are working on may be better candidates for electrical repair in general.

First picture shows after 2 hours , the new board is in, just needs tedious soldering and replacement to the rest of the camera body to finish (2 more hours).
Second picture shows attempt at determining which boards are good or bad with continuity, capacitance and resistance trials between select points on the un-powered boards.

That looks impressive!

What I got out of it was improvement my diagnostic and repair skills, which I believe is your goal also.

ic-racer said:

What I got out of it was improvement my diagnostic and repair skills, which I believe is your goal also.

Click to expand...

In any case!

I now see every repair activity as valuable no matter whether successful or not.

That's why I write my reports here and keep a log on my iPhone so that the details aren't forgotten.