Removing the mirror box with the front connector closed, servicing the shutter
When removing and installing the T90's mirror box, problems can occur with the front connector, which connects three flexible circuit boards. Contact issues can render the camera inoperable, rendering all previous repairs useless.
Instead of opening the front connector, I've developed an alternative method for removing the mirror box that leaves the front connector closed. This avoids contact problems during reassembly.
See details here:
It's happened to me several times now that I've serviced a T90, only to find the work was in vain because of unsolvable contact problems in the front flex connector. The front flex connector is located on the front release side, where the red self-timer LED is located. Three flexible circuit...
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I used this method again today with success.
To access the aperture magnet for cleaning, the mirror box has to be removed.
I also use this opportunity to clean the release magnet, which no longer works (flashing arrow on the display).
Both magnets are installed in the same place.
The battery compartment and covers have been removed.
The mirror box is unfolded and not separated from the camera. The front flex connector on the release side remains closed.
Here, the T90 is already connected to my lab power supply to test the charge motor coupling. I use this to test whether the shutter, mirror, and aperture are cocked properly after reinstalling the mirror box.
The shutter is a surprise.
The second damper has also become sticky; I had already removed the first one during the initial repair session.
So I have to disassemble and clean the shutter again.
Due to the sticking and operation of the shutter, one of the rear curtains’ slats is bent.
There's nothing that can be done to straighten it; the slats are too flexible, but I have a replacement.
The T90's vertical focal plane shutter is easy to disassemble, unlike other SLRs.
Happy is who has original spare parts
The complete rear shutter curtain (first curtain) as a spare part from a discontinued T90.
I clean the sticky parts and assemble the shutter with the new curtain.
Both black worm screws for tensioning the curtains are intact.
They break easily on the T90, so their condition should also be checked during a shutter service like today.
Cleaning the magnets
Both magnets are located at the rear, bottom left of the mirror box.
Here, on the folded-away mirror box, you can see the release magnet with its two copper coils at the top.
The release magnet in closeup.
After loosening its retaining screw …
… I can clean the contact surfaces of the magnet with benzine.
You can also remove the release magnet for cleaning from the outside, see
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
The aperture magnet is located directly above the release magnet.
You can remove it for cleaning, see
Post in thread 'Canon T90: Service and repair using practical examples'
https://www.photrio.com/forum/threa...-using-practical-examples.213586/post-2898803
but I don’t want to do that because the unfolded mirror box is unwieldy to work on.
So I bend the tip of a cleaning swab with pliers to reach the contact surfaces of the magnet. I clean again with benzine.
It looks worse than it is …
