Canon T90: Hunting for errors with the HELP and EEE codes, systematic troubleshooting according to instructions

[Andreas Thaler]

We've discussed the Canon T90, arguably the most complex 35mm camera with MF, several times here.

It's encouraging that most of the common problems can be solved DIY, see:

Canon T90: recommendations and notes

Based on my previous (repair) experiences with the Canon T90 with regard to preservation/problems/repair options, I would like to give a summary of the following recommendations/hints: Sticky shutter - gummed-up shutter blades: Can be permanently repaired, damper in the shutter area that has...

www.photrio.com

However, one problem that means the camera will fail completely has yet to be solved:

The blocked shutter with the HELP and EEE error messages in the viewfinder and on the camera's LCD.

We've discussed this at length in this thread without finding a definitive answer:

Canon T90 shows the error messages HELP and EEE: Tracking down the last major problem

One of the most common problems with the T90 is still unsolved: the shutter blocking, accompanied by the messages „HELP“ in the viewfinder and „EEE“ on the display. Until now, I assumed that the cause of this problem was dirty magnets for controlling the shutter. The T90 has two of these...

www.photrio.com

The current state of the discussion is assumimg that the two shutter magnets are dirty and are not firing. Broken plastic shafts in the shutter control could also play a role.


I'd like to restart the topic here from scratch

because, by a stroke of luck, the C & C Electronic Troubleshooting Guide for the T90 is now available, in addition to an excellent article in the SPT Journal and the Canon Repair Manual.

These error messages are dealt with in detail there providing new insights and perspectives for repair.

I'm considering this topic my main repair project for 2025; I have two T90 with this problem to work on in stock.


Highlights to come

• Removing the mirror box to get to the shutter. A particular challenge with the T90 due to the dense installation with flexible circuit boards.
• I also want to explore the T90's setting options; it even has its own built-in test mode.
• The success of these adjustments will be determined again using the Reveni Labs Camera Tester.
• Insights into the interior and technology.
• Advanced tips and hints for DIY work on the T90.

An exciting and long-term project is coming up; we'll start after Easter.

Stay tuned!

 

[Gregory_Nolan]

Great! Looking forward to your repair report.

 

[Andreas Thaler]

Great! Looking forward to your repair report.

Hopefully I won't completely lose my mind dealing with this topic!

 

[Peláez]

It will be interesting to see if he manages to fix the “EEE, HELP” error on the Canon t90 camera, although I fear that those of us who lack the necessary knowledge to undertake such tasks will have to be content with using the camera as a paperweight.

 

[Andreas Thaler]

It will be interesting to see if he manages to fix the “EEE, HELP” error on the Canon t90 camera, although I fear that those of us who lack the necessary knowledge to undertake such tasks will have to be content with using the camera as a paperweight.

I'm starting this project precisely to prevent the T90 from becoming a mere paperweight

As always, I'll aim to structure my corresponding repair report to be as understandable as possible and helpful for DIY projects.

The T90 isn't a magic box either; with the technical documentation mentioned, there's a realistic chance of making progress.

 

[Andreas Thaler]

Our candidate for a repair attempt

• The LCD display is normal.
• The mirror is triggered,
• both shutter curtains don't open,
• EEE appears on the LCD, and HELP appears on the LEDs in the viewfinder.
• After removing/reinserting the battery holder and trying again, the same sequence occurs.

 

[Andreas Thaler]

When troubleshooting, I first refer to the SPT Journal and then to the C & C Associates Troubleshooting Guide.

I follow strictly the instructions and don't go on my own.

Canon T90 Repair Guide

From the Society of Photo-Technologists Journal

learncamerarepair.com

C & C Associates Troubleshooting Guide for the Canon T90

Stay tuned!

 

[Andreas Thaler]

Observations/preparations before starting troubleshooting

• The camera is in very good external condition, there is no visible damage, and it is clean inside and out.
• The main switch has a loose connection, the LCD display is unstable.
• I inserted 4 fresh AA batteries. The open circuit voltage, measured at the battery holder, is 6.54 volts (6 volts is the supply voltage for the T90).
• I cleaned all contacts in the battery holder and battery compartment with electronics cleaner.

 

[Andreas Thaler]

Troubleshooting following the instructions in the SPT Journal

There's a separate section in the SPT Journal for addressing the EEE/HELP error.

Here's a hint for troubleshooting without opening the T90:

I try this several times without a lens attached, but the camera still doesn't work. EEE/HELP continues to appear.

Therefore, we continue with the covers removed to check the solder connections of the shutter-flex connector on the upper circuit board.

I resoldered the indicated solder points on the board, even though they looked normal. However, there was no change in status.

I continue with a voltage measurement on the DC/DC converter, which is located at the bottom of the T90 and provides various voltage levels from the 6 volt battery voltage to power the individual circuit components.

To do this, I have to remove the battery compartment.

Since I have also disconnected the cable connections from the battery compartment to the camera, I connect the T90 to my laboratory power supply.

The circuit can be reset with the yellow cable by shorting to ground, which corresponds to pulling out and reinserting the battery holder, see first troubleshooting instruction above.

On the orange cable, I only measure a maximum of 15 volts after a reset, instead of 18 volts. The voltage drops rapidly afterward. The purple electrolytic capacitor on the DC/DC board is obviously discharging.

It's possible that the capacitor is no longer fully functional. To check and measure it, I have to remove the board.

I perform a few more resets with the yellow wire to ground, and suddenly the shutter fires. Then the T90 goes back into EEE/HELP mode, and after another reset, the camera works. I run the motor in high mode to keep it moving and resolve any contact issues with the magnets.


The solution to the problem came as a surprise

What caused it, and what worked?

I can't say.

• From experience, I know that an EEE/HELP error can sometimes be resolved by triggering the camera. Perhaps it's due to dirty magnets, which then work again.
• Another possibility is that the DC/DC converter isn't providing the required voltage of 18 volts to reliably trigger the shutter magnets; in this case, it's missing 4 volts.
• The electrolytic capacitor might be the culprit; it can no longer be charged to 18 volts. However, I don't have a circuit diagram to investigate this.

Next steps

• I'll continue to shoot the opened camera and observe.
• I might remove the DC/DC converter and measure the electrolytic capacitor. I should have a replacement in my stash. I also have a replacement for the entire converter.
• Then I'll check the loose connection on the main switch.

Stay tuned!


+++

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

 

[Andreas Thaler]

The error occurs again.

The electrolytic capacitor is discharged to ground by the multimeter measurement. Anyway it should start discharging at 18 Volt.

I'm curious to see what the electrolytic capacitor measurement reveals.

 

[Andreas Thaler]

Removing the DC/DC converter, measuring the electrolytic capacitor

The DC/DC converter is housed on a separate circuit board at the bottom of the T90. I removed the converter to be able to measure the electrolytic capacitor.

For testing, I desoldered the electrolytic capacitor from the circuit board.

The nominal capacitance, according to the label, should be 33 microfarads; the tester confirms this value. The ESR value is very good at 0.12 ohms. There's no electrolyte leakage visible at the terminals. There's nothing to indicate a defect.

Before reinstalling the DC/DC converter, I measured the voltage on the converter of another T90. Here, too, the maximum reading was only 15 volts, not 18 volts. This suggests that the converter, including the electrolytic capacitor, is OK.

The converter is back in place, the voltage is correct.


First curtain: Check of the release signal

I check the release signal with the oscilloscope. Everything's OK.

Now it can only be a defective transistor or the magnet for the first shutter curtain.

I've ruled out the transistor; if it were defective, the camera wouldn't have fired in the meantime. I think a loose connection is unlikely.


All that remains is to remove the shutter, test it and clean the magnets.

Before I do that, I'll run

one more test from the C & C Troubleshooting guide.

To do this, I applied the 6-volt supply voltage through a 1-kiloohm resistor to the contact on the shutter magnet and to the orange wire where I had previously measured the voltage.

When I turned on the lab power supply, the camera clicked. When I then reconnected the previous power supply set up, the T90 fired.

That's interesting. Did the previous test revive the magnet? I don't know and will keep an eye on it. If the problem occurs again, we'll take a look at the shutter. Removing it will be quite a job.

It remains exciting

Stay tuned!

 

[Andreas Thaler]

The error reappeared after a rest period of about an hour.

Now it can only be dirty shutter magnets that aren't separating. We'll know more tomorrow.

Good night from Vienna


+++

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