Canon T90: recommendations and notes

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.

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koraks said:

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!

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koraks said:

Jiu-Jitsu and the art of camera repair.

It's going to sell. Mark my words.

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• 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.

Andreas Thaler said:

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

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Andreas Thaler said:

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.

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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.

Andreas Thaler said:

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.

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critterdoc said:

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.

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Andreas Thaler said:

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

+++

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

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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.

moggi1964 said:

Hi Andreas, just wanted to let you know my tiny magnet application is still working and the shutter fires consistently (except when left for a week or two then it takes a couple of presses to activate it).

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moggi1964 said:

Don't suppose you might have any idea what I could check to see why my film rewind doesn't work? I know the rewind has it own motor and I can hear it work but the film simply does not rewind.

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Andreas Thaler said:

That‘s great news!


Unfortunately, I can't say anything about that right now, but I'll look into it and get back to you.

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moggi1964 said:

Thanks Andreas. No rush, I've a few other cameras that I can keep shooting with

View attachment 397125

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moggi1964 said:

Hi Andreas, just wanted to let you know my tiny magnet application is still working and the shutter fires consistently (except when left for a week or two then it takes a couple of presses to activate it).

Don't suppose you might have any idea what I could check to see why my film rewind doesn't work? I know the rewind has it own motor and I can hear it work but the film simply does not rewind.

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10. Film won't rewind
Note: If the camera doesn't switch
to rewind after the last exposure
according to the DX code, check
the solder between the D flex and
the main flex, Fig. 31. If the camera
won't rewind even at the end of the
roll or with the manual-rewind
button depressed, check the
following:
Rewind motor M3
Connect a r o u n d 3V between the
pink ( + ) and blue wires at the
bottom of the camera, Fig. 29. T h e
rewind motor should run and turn
the rewind fork (the rewind motor
will run with the polarity reversed,
but the rewind fork won't turn).
Transistors TRIl, TRIZ, TRI3,
TR14
Short together pins 6 and 8 of IC9
(with or without film). The rewind
motor should run in the forward
direction and turn the rewind fork.
Short together pins 5 and 7 of IC9.
The rewind motor should run in the
reverse direction and free the fork.
If the rewind motor won't run in the
forward direction, check transistors
TRIl and TR14, Fig. 29. If the
r e w i n d m o t o r w o n ' t r u n in t h e
reverse direction, check transistors
TR12 and TR13.
IC9
With the film at the end of the roll,
check the voltage at pin 12 of IC9
and push the manual-rewind button.
Pin 12 should switch to around
1.8V. If so, yet the rewind motor
won't run, IC9 may be defective.
IC4, IC5
If you don't get the signal at pin 12
of IC9, short the S48 TP, Fig. 30, to
ground. If the rewind motor runs,
ICS is o.k. The problem may then
be IC4. If the rewind motor still
doesn't run, IC5 may be defective.

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