Canon T90: Power supply restored

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Andreas Thaler

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Today was check of my T90 family.

Some with no findings, some with the shutter blades stuck together, one with a crazy display and this one that shows nothing on the display after switching it on.

That struck me as odd, since it had worked the last time.

So something must have changed in those few months.

Always the first assumption for batteries with sufficient voltage:

Contact problems around the battery compartment.

My suspicion was confirmed when I discovered green acid residue on the bottom of the battery compartment. Not much, but telltale ;-)

Cleaning the contacts in the camera and the battery contacts did not change anything.

The T90 continued to refuse service.


So I had to check where the error is.


T90_power_1.jpg


T90_power_3.jpg


Battery compartment removal


T90_power_2.jpg


T90_power_5.jpg


And here is the reason for the refusal to operate:

The black ground wire had come loose from its soldered joint in the battery compartment.

No wonder given the severe corrosion of the soldering points at this location (arrows).


T90_power_4.jpg


Another example of how forgotten batteries in a camera can take revenge.

Without a ground connection, there is no circuit.

No function without circuit.


T90_power_6.jpg


Here is a view of the contacts in the battery compartment from the user's perspective when the camera is closed.

Little corrosion visible. But behind it it looks bad.


T90_power_7.jpg


The soldering iron was in demand.


T90_power_8.jpg


Meanwhile the battery compartment was bathed in Durgol descaler solution diluted with water to get rid of the corrosion.


T90_power_9.jpg


The black ground cable no longer seemed safe to me. I replaced it with a new one.


T90_power_10.jpg


Due to the corrosion, the soldering point on the circuit board also came off while working.

I therefore had to bridge the spot with wire in order to connect with the ground cable.

To keep the cables on the left away from the soldering work, I fixed them a little further away with Loctite.


T90_power_11.jpg


The battery compartment after cleaning in Durgol.

The green acid residues have been removed. Some rework with the probe, but the contacts are ready for soldering.


T90_power_12.jpg


The battery compartment is again connected to the circuit board via three cables.


After assembly, a test with the battery holder inserted.

Yes, the T90 was back!

The display was on - tock, tock, tock, the shutter pounded.


T90_power_13.jpg


Alive again :smile:
 
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Andreas Thaler

Andreas Thaler

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The Canon T90 has an internal battery that fails over time. Surprised that yours lasted as long as it has as mine has failed on 3 of my T90 cameras. Probably planned obsolescence by the designers of the camera.

Here the backup battery resides:

T90_9.jpg



Instruction how to replace by DrTomHi:

 
  • Dennis S
  • Dennis S
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Dennis S

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I saw that video before but an impossible task for me as the parts/screws are TOO small as when I was working as a Millwright everything require large tools. I sent them out to get the battery changed and now doesn't work properly.
 
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Dennis S

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Well I tried the one with the fresh battery and everything seems to start up fine but when I expose a frame it comes up EEE with HELP in the view finder. Take out the AA batteries and it comes back to life so I am experimenting with a roll now just to see if it does expose the frame properly but every frame taking out the battery pack is a PITA as when it first came back I found that flaw and didn't proceed until now.
 
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albada

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I notice that battery acid wicked along the entire length of the black ground wire, damaging the circuit board. Wow!
 

Dennis S

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Have you checked the shutter curtains for sticky residue?

Thanks, and will check that when I finish this roll as everything else looks good except after the exposure of a frame. Hope I get this working as the T90 is an outstanding camera.
 
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Andreas Thaler

Andreas Thaler

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I notice that battery acid wicked along the entire length of the black ground wire, damaging the circuit board. Wow!
Battery acid as well as leaked electrolyte are devilish 🥵

Images showing the mess caused by two leaking electrolytic capacitors in a Minolta XG-M.

Acid worked its way along the conductor paths over decades.

Anyway I could clean this up and replaced all four caps.

The XG-M is well again 👍


1DF73FCC-E601-41B7-8190-5D237C9F1998.jpeg


Two leaking electrolytic capacitors on the underside of the upper circuit board.


5716E5C7-25A5-40E8-BA44-1904B94B2F65.jpeg


Electrolytic condensators extracted but traces of acid left.


E4904809-82DD-49A4-BAAF-E914030AC7B5.jpeg


The acid spread to the top of the board.


2A049305-DEBF-4C68-9CE0-AA8D9A4D1262.jpeg


Cleaned up and bridged one conducter path (grey cable) as I interrupted it when cleaning.


C58BDAAB-80FE-4B2F-BDC4-ABE66CC1AD48.jpeg


Upside of circuit board cleaned.


2D5932B6-BAB5-4DCA-A571-433F754278AE.jpeg


New electrolytic condensators soldered in.


The whole story with pictures at


(German)
 
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Andreas Thaler

Andreas Thaler

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Thanks, and will check that when I finish this roll as everything else looks good except after the exposure of a frame. Hope I get this working as the T90 is an outstanding camera.

Keep us updated!

I have here more than ten T90 lurking around. Some need service/repair.

So we can go through the process 👍
 

koraks

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„The tank“ 🤠

Indeed!

Concerning the wicking of the acid: is it possible that either of the following effects played a role:
* Gravity; i.e. the camera having spent some of its time upside down with leaking batteries
* Galvanic corrosion; i.e. the leaking stuff from the battery somehow enabling galvanic corrosion between the metals in the wire (mostly copper) and the solder joint (tin, probably some lead)?
 
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Andreas Thaler

Andreas Thaler

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Concerning the wicking of the acid: is it possible that either of the following effects played a role:
* Gravity; i.e. the camera having spent some of its time upside down with leaking batteries
* Galvanic corrosion; i.e. the leaking stuff from the battery somehow enabling galvanic corrosion between the metals in the wire (mostly copper) and the solder joint (tin, probably some lead)?

I‘d like to add capillary effect - a cable means a closed insulated and narrow duct.

So acid can reach distanced locations in the camera.

I was not aware of this and the consequences till now.
 
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Andreas Thaler

Andreas Thaler

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Has anyone delt with this repair shop of the Canon T90.? https://www.ebay.ca/itm/170407398858

Me indeed several years ago.

I purchased a fully overhauled T90 which works flawlessly.

Steve is highly regarded as a T90 expert.

 

Dennis S

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Me indeed several years ago.

I purchased a fully overhauled T90 which works flawlessly.

Steve is highly regarded as a T90 expert.


OK sounds good as now I have a proper address as I don't like to ship things through eBays "Global Shipping" farce.
 

Dennis S

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Well I found some problems with the shutter so that's a bad discovery for me so I guess it will remain on the shelf with the other 2 looking pretty. I really don't know if it is really worth it to get the shutter repaired as well as the other flaws with the camera. I might just contact him to see if he has a good T90 that he might want to sell.
 

Dennis S

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Well I did decide to buy one and received a T90 from steve@cameraclinicusa.com and it's in the best shape I have seen a T90 since the late 80's. Have a good collection of FD/FL lenses and I heard a lot of good things about Steve so we settled on a price that suited both of us and received it today. I already did one short roll of Fomapan 100 and developed it in PMK and it is still drying but looks good so far. I was still amazed on how complex settings are and settled with Aperture Priority this time with an FD 50 f1.4 SSC lens. I always liked the size and the feel of this camera with the great metering as well. 😎 😎🤣😄
 
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