Canon T90: The infamous HELP/EEE error fixed through guided and systematic troubleshooting

[Andreas Thaler]

There's a problem connecting the charge motor to the shutter mechanism. The motor is running, but it's not driving the mechanism. I followed the instructions in the SPT Journal.

I don't know if this was already the case before I disassembled the T90, since it wouldn't fire and displayed EEE/HELP. This might be the cause of the problem (?).

I'll have to take a closer look to make any progress here.

 

[Andreas Thaler]

The charging motor is housed in the handle. I connected it directly to a 2-volt input voltage.

It drives the shutter charge lever and the mirror charge lever (white arrow) via a transmission. (The shutter is removed.)

The transmission is located on the left under the motor flex, which is heavily wired. I can only lift the flex partially to get to that spot. I would have to do extensive disassembly.

I decide to abandon the unit and destructively remove the flex. It's important to me to understand its function.

An eccentric (white arrow) via a lever (yellow) drives the mirror charge lever (green) and the shutter charge lever (not visible here).

The problem is that the motor isn't driving the eccentric. This means the shutter and mirror box aren't tensioned. The motor rotates, but there's no power transmission.

I can't determine the cause. So I have to give up on this T90 as well.

 

[Andreas Thaler]

Of course, I'm not giving up

I've already learned a lot about the T90 through this project and have a process for testing the EEE/HELP error and removing mirror box and shutter. I've also been able to study, clean, and test the shutter.

Now it's time to determine whether the EEE/HELP issue is related to the charge motor and its transmission. That would be an explanation, because the shutter works perfectly.

I'll therefore see if I have another T90 that I can disassemble and study the function of the charge motor. Then I can swap the parts and try reassembling it.

Stay tuned!


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

 

[Andreas Thaler]

Third attempt with a like-new T90

I still have one last T90 with the EEE/HELP error.

The camera is like-new, but I had already removed the DC/DC converter and the shutter release magnet at an earlier point.

I'll replace these two parts from my spare parts stash.

Then I'll run the tests again, remove the shutter, clean and test it, and hopefully, this time the charge motor coupling will work.

The electrolytic capacitor on the spare DC/DC converter is fine.

The release magnet is with 63 ohms resistance (67 ohms spec) doing well in the race.


I will report back with the result of this third attempt.

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Does all this make sense?

It's a lot of work, no success yet.

Wouldn't it be wiser to give up?

A resounding no!

Because with every project, you learn something new; problems lead to new insights; you get practical experience. And there are already interim results.

Last, but not least: working is fun

 

[Andreas Thaler]

We're back in the game

After reinstalling the release magnet and DC/DC converter on the third T90, it - as expected - fires the mirror, both shutter curtains don't respond, the charge motor starts running, and EEE/HELP is displayed.

This puts us back in the game; a new round of troubleshooting begins.

I'll run the (extended) tests again and this time pay attention to the coupling with the charge motor when disassembling.

Stay tuned!

 

[Andreas Thaler]

The secret of the charge motor has been revealed, we are on track

Since the coupling between the charge motor and the shutter also didn't work on T90 #3 – the motor rotated but didn't cock the shutter – I ruled out a defect.

I went through my documentation again, disassembled a discontinued T90 to study the power transmission path from the motor to the shutter, and realized my mistake: I had connected the winding motor to my lab power supply and not the charge motor, which is located in front of it in the handle.

„Ich stand auf dem Schlauch“ is a German saying that Google translates as „I was confused“

A misunderstanding that cost me T90 #2 yesterday.

Now I can test the clutch function during assembly as stated in the SPT Journal,

With new insights, I'm moving on to #3.


I ran all the tests again

and everything points to a problem with the shutter magnets. Or a sticky shutter.

So I removed the shutter for examination.

There was a screw here at the sensor unit that wouldn't come off. I could only insert the screwdriver at an angle because the rear structure was protruding. I used the diamond cutter on my Dremel to remove the screw head.

I will later substitute the screw with epoxy.

The shutter housing is glued to the rear with a seal.

Shutter removed.

Traces of oil on shutter curtains and part of the front shutter housing.

This could be the cause of the EEE/HELP error.

Here, in the handle, is the charge motor with its two connectors.

To connect the laboratory power supply and test the function of the clutch mechanism, the trigger unit must be removed.

The charge motor in action. Now the coupling mechanism on the camera base is also moving. Finally!

 

[Andreas Thaler]

I'm going to take a look at the shutter and disassemble it now.

In any case, I have the shutter from T90 #2, which I serviced yesterday, just in case.

An exciting journey through the T90 world.

Stay tuned!

 

[Andreas Thaler]

Removed parts and a second, already serviced, Copal S shutter.

 

[Andreas Thaler]

Testing the shutter mechanism, transistor TR1 and magnets

The shutter can be manually cocked and both shutter curtains released.

This is an important result, as during the previous test, the magnet of the first shutter curtain did not trigger electronically when installed.

This could indicate that the magnet is dirty, as the more oil is visible on the unit. Then the contact surfaces can stick together, even though the magnetic force is canceled out by the coil. The magnet then does not separate and the curtain does not start.

I will clean the magnets and their two associated switches.

Before I open the shutter to clean it, I test transistor TR1 on the shutter control, which is also mentioned as a possible cause of the EEE/HELP error.

Since I can't test the transistor built into the circuit, I desolder it with hot air.

As an SMD component, it is soldered onto the surface of the circuit board.

To attach it to the spring hooks of my electronic component tester, I solder tinned copper wire onto the terminals as an extension.

Now the transistor can be measured automatically.

The tester displays the most important parameters.

No errors, the transistor is OK.

Soldered back into place.

Removing the shutter cover.

Some oil is visible. I don't know where it's coming from; perhaps from the shutter mechanism or the mirror box.

For a thorough cleaning, I have to remove the curtains. The sticky damper also needs to be removed.

It continues tomorrow.

Stay tuned!


+++

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

 

[Andreas Thaler]

Disassembling and cleaning the shutter

This Copal S shutter is easy to disassemble and clean.

Only one screw secures the cover, the top of two springs stays in place, no dampers need to be adjusted, the alignment of the parts is clear, and the assembly is straightforward.

The shutter is in the released state. The first curtain (opener) is compressed, the second curtain (closer) is expanded.

Spring 1/2

Oily traces on the separator.

Spring 2/2

This is the cause of the contamination. The second curtain damper is decomposing; it's sticky and secreting oil that spreads inside the shutter.

This is its back, the damper for the first shutter, which is the cause of the infamous sticky shutter. This damper causes the most problems; it can be removed from the outside.

Here I can separate and remove it cleanly.

I'll leave the larger damper installed. It stabilizes the shutter, and it will be a long time before it starts secreting oil in that amount again. If any of it gets on the curtains, I'll clean it from the outside.

Overview

Cleaning with acetone and blotting paper strips.

The shutter is cleaned and reassembled.

 

[Andreas Thaler]

Testing the reassembled shutter and the charge process via charge motor M2

Releasing the curtains manually and electronically after reassembly of the shutter. Everything's fine.

The magnets already trigger with an input voltage of 2 volts (3 volts spec). Anyway I'll clean them, along with the switches.

The shutter is reinstalled for testing the charge process via charge motor M2.

A strange behavior occured.

When I cocked the shutter outside the camera and manually/electronically released the curtains, everything worked.

But when I installed it inside the camera and let the motor cock it, the first curtain wouldn't release.

It took me hours to find the cause.

The lower shutter fastening screw was too high and blocked the charge lever. This prevented the shutter from firing.

Here you can see the marks left when the charge lever was moved over the screw. The motor provided sufficient power for cocking but the lever could no longer swing back freely. It got stuck halfway.

There are two variants. The screw on the top left has a higher head. In the lower - wrong - position, under the charge lever, it caused the blockage.

Here is the correct arrangement.

 

[Andreas Thaler]

The next step is cleaning the magnets and switches. Then I'll test the curtain travel times before assembling the T90.

Stay tuned, it's an exciting journey!

 

[Andreas Thaler]

Cleaning magnets and switches

We already saw this with the T90 #2, see earlier in the thread.

The armatures of the permanent magnets are lifted and the contact surfaces are cleaned with benzine.

Cleaning the gold-plated switches with electronic cleaner.

 

[Andreas Thaler]

Setting the curtain travel times on the camera tester

The first shutter curtain (C1) was 3.28 milliseconds, the second curtain (C2) at 3.22 ms, at a spec of 2.7 ms for each.

This meant that the T90 produced evenly exposed images, but the shutter speeds would have been shifted toward slower. Therefore, I had to tighten the springs of both curtains.

On the T90, this is easily done using two worm screws that can be turned in either direction. Also, the shutter doesn't have to be removed for this; the two screws are accessible after partial disassembly:

once on the bottom (C1) …

and once on the top (C2).

To adjust the shutter, I mounted it in the back of the camera and connected the charge motor M2 to my lab power supply. After each shutter charge via the motor, I manually triggered the two shutter curtains on the camera tester using a probe.

After a few passes, the curtains travel times are adjusted. The spec is 2.7 ms (+/- 0.2 ms).

 

[Laurent]

this is fascinating. I'd be unable to do this, but stand in awe at your reports!

Glad I sold my T90s as I'd be tempted to fix them and I know I would not be able to go that deep!

 

[Andreas Thaler]

This completes the testing and service work and it is time for assembly, which begins with inserting and coupling the mirror box.

This is critical, we keep our fingers crossed for the T90

 

[Andreas Thaler]

this is fascinating. I'd be unable to do this, but stand in awe at your reports!

Glad I sold my T90s as I'd be tempted to fix them and I know I would not be able to go that deep!

With good guidance, which Larry Lyells gives us, it's doable. But it requires patience; the T90 doesn’t always make it easy

We haven't landed on Earth yet, so a lot can still go wrong …

 

[Andreas Thaler]

Assembly successful, EEE/HELP error fixed, very good results on the camera tester

The assembly went smoothly; inserting the mirror box and connecting the mechanism to the motor worked right away. I did some tests along the way.

Before the finish line

At the very end, there are still many cables to solder from the top cover to the circuit board.

The EEE/HELP error has been resolved, and the T90 is firing again

What was the cause?

I suspect it was dirty magnets that were no longer releasing, as a test showed. Manually releasing the removed shutter should have cleared the blockage. Perhaps the slightly sticky shutter blades also played a role.


Results on the Reveni Labs Camera Tester

Testing the shutter at the fastest (most critical) shutter speed of 1/4000 second.

The shutter test results in summary:

Even exposure of the image, shutter speeds close to the target.

Initially, the values were bad, but the shutter obviously needed to get used to the movement again. After a few series in high-speed mode, the speeds were stable.

The result of an exposure in Program Mode with Canon nFD 50/1.8.

This could be better, but the lens also plays a role, it must be able to form the aperture values without deviations.

The practical test with film will show what the T90 can do.

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Conclusion

• Hopefully, the infamous EEE/HELP error has lost its horror. It can be addressed with systematic troubleshooting, guided by the best experts.
• The repair requires, in particular, good soldering skills and patience. The T90 is complex, and it takes time to get the hang of it.
• Without the fantastic instructions from Larry Lyells in the SPT Journal, the equally excellent C & C Associates Electronic Troubleshooting Guide for the T90, and the Canon Service Manual, this mission would have been hopeless. Many thanks to the authors, even though master Larry Lyells is no longer with us. We DIY repairers should be deeply grateful to him.
• This project is further proof that DIY repairs to electronic SLRs are possible. You just need to approach it systematically and with instructions.
• Good luck to everyone working on this wonderful camera!

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