Canon T90: recommendations and notes

[Andreas Thaler]

But whether it's a mechanical problem with the shutter or with the circuit board on the shutter, I would have to work my way through the camera to get there.

To remove the mirror box, Larry Lyells describes about 30 steps during dismantling. The chance of not breaking anything or getting everything right when assembling is small, very small.

And even if I should manage to do it, I have to understand the processes at the shutter in order to fix something there. Or the error lies in the mechanics of the mirror box which seems even more complicated to me.

This means that troubleshooting only if there is suspicion involves a lot of effort and risk.

I should listen to Thomas Tomosy, who writes about the T90:

It is not recommended that you attempt to repair this camera. It is included here only to show what you’re up against when it comes to fully automatic electronic SLRs.

Thomas Tomosy, Camera Maintenance & Repair, Book 1, Buffalo/NY: Amherst Media, 1999, Kindle edition, position 2218.

 

[koraks]

I admire your patience in even getting to this point. I opened up one of my EOS30's the other day to see if I could easily spot its battery drain & (supposed) door latch problem. Removed the front and bottom covers, and quickly decided I found it still worked well enough to not risk making it any worse!

 

[Andreas Thaler]

I admire your patience in even getting to this point. I opened up one of my EOS30's the other day to see if I could easily spot its battery drain & (supposed) door latch problem. Removed the front and bottom covers, and quickly decided I found it still worked well enough to not risk making it any worse!

Temptation and failure - maybe I should write a repair romance novel

 

[koraks]

Jiu-Jitsu and the art of camera repair.

It's going to sell. Mark my words.

 

[Andreas Thaler]

Jiu-Jitsu and the art of camera repair.

It's going to sell. Mark my words.

 

[Andreas Thaler]

Also impressive under the hood: Canon T90


Final thoughts on the T90

• I just have looked through Canon's service manual for the T90 (suaudeau.eu). Right at the beginning, additional information material that is not available is pointed out. Material that we lack for deeper understanding.
• After replacing certain parts such as ICs, extensive adjustments must be carried out, among other things. with devices that are also not available.
• A limit of what is possible in DIY service and repair has been reached here, at least for the hobby workshop at home. But I am not aware of any workshops that would accept the T90 for service, with the exception of one workshop in the USA.
• Anyway there is no reason to be sad, almost all common problems with the T90 can be resolved or prevented, as we have seen
• And if an electronic camera still works after around 40 years of manufacture, it should continue to do so for another 40 years. All I see here is quality and electronic circuits do not suffer from wear and tear, even if components such as electrolytic capacitors can age or fail due to overload.
• Since the T90 only has 6 volts of input voltage, which is converted internally to 18 volts, overloading should not be an issue, in contrast to devices powered by mains voltage generating heat by power dissipation.
• The T90 is also excellently sealed against dust and dirt, but there is no seal against moisture.
• The shutter and mirror mechanism are solidly designed. The three electric motors should run without wear.
• The T90 is also insensitive to shocks and impacts, as shown by the infamous method against stuck magnets. Here the camera is placed hard or worked with a rubber mallet.
• If you want to work with the T90, you should buy several copies as a backup that are kept fit through regular exercise. You get a lot of performance for relatively little money.
• It is a camera still far beyond its time, the best photo machine ever made for manual focusing.

 

[Laurent]

• It is a camera still far beyond its time, the best photo machine ever made for manual focusing.

I could not agree more. Took more than 20 years and the EOS 3 to reach the same level (for me at least), with the caveat that the EOS3 (which I sold, may be out of stupidity) needed the booster and 8 batteries to match the T90 (save for autofocus of course)

 

[Andreas Thaler]

Update:

Canon T90: Cleaning the mirror magnet

I have a T90 here whose mirror magnet no longer works. The usual symptom of a quiet clicking sound and a flashing arrow in the display occurs. The recommended cure of removing the front cover and activating the - easily accessible - magnet with a magnetized screwdriver tip works with patience...

www.photrio.com

 

[Andreas Thaler]

Update:

Canon T90: Fixing dropouts on the control wheel

A more annoying than serious problem with the Canon T90 is the control wheel on the handle, which turns in notches that sometimes no longer make contact. You then have to turn the wheel one or two positions further in order to be able to set a shutter speed or an aperture value, for example. I...

www.photrio.com

 

[Andreas Thaler]

1. Shutter does not release - flashing arrow in the display: The cause is the mirror magnet, which no longer works due to magnetization. Can be fixed with a magnetized screwdriver blade or replaced with only little disassembly.

Based on recent findings:

1. Shutter does not release - flashing arrow in the display: The cause is the mirror magnet, which no longer works due to contamination which can be cleaned with electronics cleaner or isopropyl alcohol. Alternatively try to fix with a magnetized screwdriver blade or replace with only little disassembly.

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

 

[Andreas Thaler]

Updates:

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

Canon T90 and T70: Rescuing victims of leaked battery electrolyte

From a collection of cameras, I chose these two T90s and one T70. They all have one thing in common: their battery compartments cannot be opened because the batteries have leaked. The battery acid has cemented the battery holders and the battery compartment cover of the T70. When I tried...

www.photrio.com

 

[critterdoc]

I have just found a note from Thomas Tomosy (Camera Maintenance & Repair, Book 1) on how to lift the trigger switch assembly without damaging the cable connections. Then the contacts on the adjustment wheel can be cleaned.

To do this, the battery compartment must be removed and the cable harness installed in the handle must be loosened.

If anyone is interested, I would be happy to show it on one of my abandoned T90s.

Please do! After 50 yrs. as a CET repairing video equipment before moving into robotic repair/programming, I had the chance to visit with a film camera (movies&still) in Toronto. It was 1994 & he was repairing/recalibrating a T90. I thought some Bolex & Leica gear was overcomplicated but Holy knotholes, Batman, when I saw the circuit boards, wiring harnesses & assorted bits of that T90 laid out on the bench, I was appalled! Reminded me of nothing less than an electronic train wreck! The repairmans secret?: A SECOND T90 in perfect shape to use as a metering& exposure standard! I didn't even ask what his hourly rate was. Nonetheless, he did say that the "injured" T90 would be good for another couple decades with a bit of care.

 

[Andreas Thaler]

Please do! After 50 yrs. as a CET repairing video equipment before moving into robotic repair/programming, I had the chance to visit with a film camera (movies&still) in Toronto. It was 1994 & he was repairing/recalibrating a T90. I thought some Bolex & Leica gear was overcomplicated but Holy knotholes, Batman, when I saw the circuit boards, wiring harnesses & assorted bits of that T90 laid out on the bench, I was appalled! Reminded me of nothing less than an electronic train wreck! The repairmans secret?: A SECOND T90 in perfect shape to use as a metering& exposure standard! I didn't even ask what his hourly rate was. Nonetheless, he did say that the "injured" T90 would be good for another couple decades with a bit of care.

Thank you for remembering Thomas Tomosy!

We owe him a lot, he laid the foundation for many DIY repairers with his six books.

Unfortunately he passed away last year:

In memory of Thomas Eugene Tomosy

Thomas Eugene Tomosy is known to many of us as the author of classic repair books on cameras and lenses. I wanted to find out more about him and found this information. According to this, Thomas passed away in Canada in 2023 at the age of 84. Based on the information given, I assume that this...

www.photrio.com

 

[Andreas Thaler]

Investigating and repairing the T90 shutter by @joe_laroids

Post in thread 'Canon T90 shows the error messages HELP and EEE: Tracking down the last major problem'
https://www.photrio.com/forum/threa...wn-the-last-major-problem.208254/post-2861664

 

[Andreas Thaler]

C & C Troubleshooting Guide for the Canon T90

 

[Andreas Thaler]

View attachment 352997

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:

1. Sticky shutter - gummed-up shutter blades: Can be permanently repaired, damper in the shutter area that has become sticky can be removed without dismantling. Lighter fluid/acetone on blotting paper and, if necessary, a probe are used.
2. Shutter does not release - flashing arrow in the display: The cause is the mirror magnet, which no longer works due to magnetization. Can be fixed with a magnetized screwdriver blade or replaced with only little disassembly.
3. Shutter does not release - “EEE” is displayed on the display and “HELP” in the viewfinder: If gummed-up shutter blades are no longer moving see 1. Other cause: locking magnets that do no longer separate. This can only be fixed by deeply dismantling the camera; I am not aware of any report on this yet.
4. Light seals and mirror shock absorber should be durable in the long term. I haven't had a T90 with any problems yet.
5. Any corrosion in the battery compartment due to leaking batteries: One should always check whether the decomposing battery acid has already worked its way through the connection cables towards the circuit board. Dismantling necessary, if necessary cleaning and replacing the soldering points/wiring.
6. The T90 should be moved regularly to prevent problems with the magnets (2., 3.). I trigger my T90s every month and check the function.
7. A display that displays incorrectly can be replaced. Dismantling the top cover and soldering skills required.
8. Backup battery for ASA setting: Same as 7.
9. Dial wheel with dropouts - for example, increasing aperture values are not displayed per click. Contact error, probably due to oxidation. Point accessible by dismantling, but complication due to short cabling to the trigger. Therefore cleaning of the contacts can be tried by turning them often.

The T90, introduced in 1986, is a fascinating camera that still has the potential to overwhelm due to its diverse features.

Known as “the tank”, it is robust and valuable. The mechanics are heavy duty and designed for hard work.

Together with the FD lenses and system flash units, you get a fully motorized complete package for first-level analog photography

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

To be updated soon.

 

[Andreas Thaler]

Update (last status was from November, 11 2023):

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:

1. Sticky shutter - gummed-up shutter blades: Can be permanently repaired, damper in the shutter area that has become sticky can be removed without dismantling. Lighter fluid/acetone on blotting paper and, if necessary, a probe are used.
2. Shutter does not release - flashing arrow in the display: The cause is the mirror magnet, which no longer works due to magnetization contamination. Can be fixed with a magnetized screwdriver blade by cleaning or replacing with only little disassembly.
3. Shutter does not release - „EEE“ is displayed on the display and „HELP“ in the viewfinder: If gummed-up shutter blades are no longer moving see 1. Other cause: locking shutter magnets that do no longer separate. This can only be fixed by deeply dismantling the camera; I am not aware of any report on this yet.
4. Light seals and mirror shock absorber should be durable in the long term. I haven't had a T90 with any problems yet.
5. Any corrosion in the battery compartment due to leaking batteries: One should always check whether the decomposing battery acid electrolyte has already worked its way through the connection cables towards the circuit board. Dismantling necessary, if necessary cleaning and replacing the affected soldering points/wiring.
6. The T90 should be moved regularly to prevent problems with the magnets (2., 3.). I trigger my T90s every month and check the function.
7. A display that displays incorrectly can be replaced. Dismantling the top cover and soldering skills required.
8. Backup battery for keeping the ASA value: Same as 7.
9. Dial wheel with dropouts: For example, increasing aperture values are not displayed per click. Contact error, probably due to oxidation. Point accessible by dismantling, but complication due to short cabling to the trigger. Therefore cleaning of the contacts can be tried by turning them often. The affected contacts of the wheel are not accessible from the outside, so removal is necessary for cleaning. As a shortcut, you can also try moving the wheel frequently to make the contacts conductive again.

 

[Andreas Thaler]

As always

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