Canon T90: Service and repair using practical examples

[Andreas Thaler]

Shutter: replacing the sticky damper?

It's clear that the sticky damper for both shutter curtains needs to be removed to prevent the T90 from becoming inoperable sooner or later.

I wonder if a replacement is necessary.

Assuming that no part of the T90 is installed without purpose, the answer is yes.

However, the question remains as to what functions the damper performs.

These could be

1. Catching the shutter curtains after they have triggered in order to relieve the load on the associated suspension.
2. Prevent the slats from bouncing back into the film window.
3. Enabling the fastest 1/4000 second, where release and cocking occur in a flash and the shutter slats must follow accordingly without vibration.

2 and 3 would have to be determined by tests on film, whereby the camera tester should also indicate irregularities.

1 seems to me to be the most important point. With heavy use of the shutter, especially in HIGH motor mode, the missing damper could accelerate shutter wear.


Deduction

• If the T90 is primarily stored in a closet after service, including removal of the damper, all three points are irrelevant. This applies, for example, to collections.
• When using the camera for taking photographs, you should take a few test shots to determine if there are any irregularities in the exposure.
• The more heavily the T90 is used, the higher the likelihood that the shutter will wear out sooner if the damper is missing. However, I don't see any area where wear could occur. The slats are extremely durable and elastic. The mechanism of the shutter is made almost entirely of solid metal.

Conclusion

• If you're going to invest effort in shutter service, you should also replace the missing damper.
• Replacement dampers are no longer available, and even if they were, they would be sticky, thus can‘t it be removed from spare T90s.
• Therefore, one option would be to make a replacement out of silicone.
• As you can see in the photos above, the damper also served as a spacer between the layers of the shutter. This has to be considered.

Action

At the next service of a T90 I will look into how the damper can be replaced.


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

 

[Andreas Thaler]

An extremely rare phenomenon: an intact shutter damper

Today, I removed the shutter from one of my spare T90s and recovered the damper, which is completely intact and not sticky. At least, I hadn't seen that before.

This gives the opportunity to explore the damper's exact location and function.

The T90 shutter partially disassembled, looking at the back.

The shutter is in the released position.

The first curtain (opener) is folded down, the second curtain (closer) is folded out.

The first curtain rests on a part of the damper at the bottom left.

The same situation, but with the first curtain removed. You can see that the damper also supports the second curtain.

The damper is removed from its position.

Back of the damper.


The well-known shortcut, which involves removing part of the damper from the outside, only frees the first shutter curtain of sticky residue. The second curtain cannot be reached this way.

Therefore, for a complete and thorough cleaning, the shutter must be removed and disassembled.

The fact that cleaning the first curtain - so far possible from the outside - is sufficient to make the shutter functional is due to the fact that the second curtain has only a small contact surface on the damper compared to the first curtain.

Therefore, a contamination of the second curtain often does not play a role, as it is only slight.


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

 

[Andreas Thaler]

Removing/inserting the worm screws for adjusting the curtains travel times

Since these plastic worm screws can break, I looked into how to remove and reinsert them.

On this occasion I also acquired spare parts for future replacement.

The screw for the second shutter curtain can be pushed out or pulled out. To do this, turn it to break the greenish sealing varnish.

It may help to turn the screw further to relieve the pressure on the spring that is tensioned by the gear below.

Then, the worm screw can be removed, albeit with some resistance caused by the spring and transferred to the gear.

The principle is the same for the screw for the first shutter curtain.

However, a circlip must be removed first.

Both screws can be reinserted with a little pressure and coupled with their gears.

The pair of screws, left for the first and right for the second shutter curtain.

The two hybrid shutter magnets have been removed.

If they are dirty and no longer trigger, the T90 displays EEE/HELP.

However, this can also have other causes.

For the spare parts stock including the intact damper.


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