Canon T90 and T70: Rescuing victims of leaked battery electrolyte

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Andreas Thaler

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gorbas said:
Andreas, your extraordinary works gives us, ordinary guys with minimum technical knowledge, hope that we also can fix some of our cameras so they not become E waste. Thank you!
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I'm just a crazy guy, but be careful! The job is dirty sometimes!
 
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Andreas Thaler

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The current score is 3 : 5.

I was able to restore three of the rotten Canon SLRs from the lot, I messed up one and a T90 is still waiting for its leaking batteries to be recovered.

We'll continue here soon
 

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I hope that you are wearing eye protection when using the dremel tool and drill.
Excellent work on bringing the Canons back to life.
 
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Andreas Thaler

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I'm going to take the cover off the T70 to take a look underneath.

Hopefully I can reach the battery contact exit inside the camera to check the circuit board for traces of electrolyte.

I don't need a replacement for the milled screw, the thread is stuck and I can't remove it. Nevertheless, the base plate is held in place with the remaining screws.
 
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Andreas Thaler

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Canon T70: removing the covers, visual inspection, cleaning

Since the T70 was heavily contaminated with electrolyte in and around the battery compartment, I would like to take a look under the hood to see what it looks like there.



Some dirt on the outside.


Removing the covers



After removing the front panel, the top cover can be lifted. Be careful, there are seven cables soldered here.

To remove the front panel and top cover, simply loosen the screws.

The retaining plate on the side for the backdoor lock is similar to that of the T90. Here too, the two screws must be loosened in order to be able to remove the front panel.




Overview


Visual inspection



Pressure switch with contacts.




The battery chamber, there is still some electrolyte here.




Dirt on the gearbox …




… likewise here.




The camera has been worked on, as the signs of wear and tear show.




The left part of the upper board.

Here you can see a button cell.

Larry Lyells:


SPT Journal: November-December 1986

Society of Photo-Technologists Journal
learncamerarepair.com




The right part of the upper board with the LCD.




The contacts of the main switch under the top cover.




Documentation of the soldering points for desoldering the top cover.






The lithium battery with a nominal voltage of 3 volts has an overvoltage of 3.2 volts after an estimated 38 years and significant use of the camera.

Unbelievable!
 
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Andreas Thaler

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In order to desolder the black cable, I remove the adhesive tape over the two soldering points.

It is stuck tight and therefore takes some time.




The top cover is removed.

This makes it easier to clean and it doesn't get in the way when working on the camera.




Removing the clutch plate with wipers for transmitting the positions of the main switch. I will also clean the contacts here.


Summary visual inspection/decisions
  • Since I cannot remove the battery chamber with the contacts, I will limit myself to cleaning the outside. The contacts inside look good and the most important thing is that this type of electrolyte does not attack metal.
  • I will use this opportunity to remove dirt from under the covers and clean all accessible contacts.
  • For a thorough CLA (clean, lubricate, adjust) the camera would have to be disassembled in depth. I will not do that because I am not trained in it and it is not necessary as long as the camera works.
  • Anyway I will check the shutter speeds and the automatic lighting control with the Reveni Labs Camera Tester.
  • Focusing screen and mirror are clean, the LEDs in the viewfinder work.

+++

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

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I should have used my grounded work mat here to prevent damage to the electronics from electrostatic discharge.

Too little sleep makes you lazy and careless …

It will continue soon
 
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forest bagger

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Andreas Thaler said:
I should have used my grounded work mat here to prevent damage to the electronics from electrostatic discharge.
Click to expand...
Don't feel uneasy, Andreas. I dismantled many cameras, older than this t70 and much newer, without any ESD means - no problems until now.
Only the discharging of flash capacitors is very important.
 
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Andreas Thaler

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Cleaning

If you do the cleaning with love, patience and care, the result will be best










I remove electrolyte residues with Durgol descaling solution.

If it foams when dripping on, the solution is active.

Wipe with distilled water, making sure none of it runs into the camera. Dry with Kim Wipes or other lint-free cloths and cotton buds.

Perfectionism takes time and the result doesn't get much better. That's why I don't overdo it.

For those who are interested, I removed the light residue on top of the handle in the final step.




Such damp and wet work can be done well on an absorbent mat that is usually used for changing babies.






Dirt and greasy residues can be removed using isopropyl alcohol on cleaning swabs.

Plastic, prints and engravings should not be affected by this. But it makes sense to test it first.

On this occasion I noticed the coating in the rear battery compartment and removed it.




Electronics cleaner for contacts.




Universal cleaning foam for plastic parts.








Cleaning with water is not necessary after wiping …






… here, however, because the foam under the film pressure plate is otherwise not accessible.
 
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Andreas Thaler

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Here, too, I rinsed with running water afterwards.




Once everything is dry, it's time to assemble it.
 
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Andreas Thaler

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Assembly and check: There is a problem with the trigger



All cables on the top cover are soldered back onto the circuit board.




A piece of insulating tape replaces the removed tape over the two cable connections.




After assembly, the camera worked. But when attaching a lens, the shutter no longer released.

Anyway the exposure metering started when I tapped the shutter button.

I suspected a contact problem.






So I removed part of the switch unit to look.




The shutter release switch can be seen here.

Two contacts are on top of each other.

When you touch the shutter release button on the top cover, both contacts make contact and the exposure metering system switches on (green arrow).

If you press the shutter release button all the way down, another contact underneath closes and the shutter releases (red arrow).

The strange thing was that the shutter was released when I pressed both contacts at the back.




I found that the red plastic film over the silver metal plate had shifted. This was obviously affecting the shutter release.

The plate conducts and creates the click when the shutter is released by being pushed through.




Here the assembly is complete again.




Now it works again with the trigger.




Test with lens.

The automatic program controls the shutter speed and aperture depending on the light intensity.

Everything is plausible.








Mounting the covers.




Pliobond for fixing the rubber coating on the handle.




Here it is again, the T70.

But now full of life
 
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Andreas Thaler

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Not new, but clean again.




This is what the T70 looked like before






Here too, things looked different before




The T70 indicates that the film has been rewound and can be removed. This happens even without a film cartridge inserted.

Everything works


+++

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

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Great report of your work, as always. I have never owned a Canon camera, but this thread really stirred my interest.
 
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Andreas Thaler

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Gregory_Nolan said:
Great report of your work, as always. I have never owned a Canon camera, but this thread really stirred my interest.
Click to expand...

Thank you!

The T70 is surprisingly heavy and solidly built from metal.

The plastic covers give it the image of a „plastic camera“, but the material has the well-known advantages over metal.

Integral and selective metering, fully automatic, also continuous, film transport, shutter priority, program automatics for normal, telephoto and wide angle, and it is small.

According to the manual, the buffer battery and LCD last five years. Here it is about 38
 

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Hola mi nombre es Israel soy de México tu trabajo es fabuloso soy fan de la Nikon F4 gracias a ti he podido aprender como es su interior siempre estoy buscando tu contenido tuve la Canon T-90 y Canon T-50 y nuevamente gracias a ti se como es su electrónica tienes todo un equipo que solo pude tener en mis sueños el obturador de mi F4 esta roto ya lo compre en e-Bay pero he decidido no cambiarlo por mi cuenta ya que no tengo experiencia en soldadura lastima que vivas tan lejos seria un honor verte trabajar reparando estas joyas que no son del pasado son de nuestro tiempo.
 

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Cuando veo tu trabajo me quedo sorprendido de como te es fácil reparar las cámaras, tengo mi F4 descompuesta desde hace 5 años la compré con un vendedor de Japón salió muy mala, primero tuvo una falla con el sensor de carga la llevé a reparar, después un buen día que estaba probándola empezó a disparar sin parar, sin abrir el obturador, tan luego presionaba el botón para tomar lectura, tengo los manuales de reparación, todo apunta a una falla en los transistores que controlan los electroimanes conseguí el obturador nuevo en EEUU pero el técnico me cobra caro USD 132 por cambiarlo, tu dices que escribes solo, no es así yo también lo hago en Nikonistas.com en el hilo que un compañero abrió sobre la F4 del cual solo yo y unos cuantos lo mantenemos vivo, Nikon F4
 
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