Canon T90 and T70: Rescuing victims of leaked battery electrolyte

Andreas Thaler

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From a collection of cameras, I chose these two T90s and one T70.

They all have one thing in common: their battery compartments cannot be opened because the batteries have leaked.

The battery acid has cemented the battery holders and the battery compartment cover of the T70.




When I tried to remove the battery holders from the T90s, the locking knob came off, indicating that its metal holder was being corroded by acid.




Here you can get an idea of what the battery chamber underneath looks like.






There is still a film inserted here and it has already been transported. It can be pulled out.

The Elite Chrome will be a welcome test film for the transport system of the T90s, but of course it will not be developed




The T70 looks similar.

There is paper stuck to the handle and crystallized battery acid can be seen on the battery compartment lock.

The mirror boxes and film windows of all cameras are clean.


The good news is

that the battery compartment on the T90 can be completely removed. I have a replacement for it.

It remains to be seen whether the battery acid has migrated via cables to the circuit board in the housing.

After restoring power supply, connections and terminals I will check the other functions.

I will try to dismantle the T70, otherwise I will probably not be able to get to the scene of the horror.


It will take a little while before we start here.

First I will take care of the defective control wheels of two T90s that come from the same batch.
 
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Andreas Thaler

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It's an interesting thing.

Here you can see the battery compartment of another T90 removed. The batteries are inserted into a battery holder.

The T90's circuit board above it is well protected from battery acid leaking out, but vapors can rise up and cause corrosion in the camera. The insulated cables are also good acid bridges.

It will also depend on which type of battery was forgotten here. Newer Duracell batteries seem to be less aggressive to me, for example, and they don't eat away at contacts.

The fact that the battery holder lock has fallen off on both T90s and that turqouise residue is visible on the outside of one of the T90s suggests that there has been some damage.

We'll see.
 
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koraks

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FYI - battery acid (sulfuric acid) is something associated with lead-acid batteries. In carbon zinc and alkaline batteries as used in these cameras, you encounter alkaline electrolytes, not acidic ones. It makes a difference in terms of failure modes and affected components. There's also a difference in terms of battery chemistry, i.e. whether "alkaline" or zinc-carbon batteries were used. Rechargeable batteries are yet another story; cameras of this age may have had leaky NiCd's inside them, which would of course be particularly nasty due to the traces of cadmium you might encounter. The electrolyte is still potassium hydroxide, similar to alkaline batteries. So you won't find much acid in there.
 

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To neutralize the alkaline electrolyte from most batteries you are likely to encounter in cameras, you can use a weak acid such as white vinegar or lemon juice: brush off any loose crud, dab on the acid, and leave it there until the fizzing stops. This can take a while, but if it seems to be taking forever, dab a bit more acid on. After drying, scrape the remaining crud off, then re-clean with isopropyl or whatever, and your contact polish of choice. For some types of Li-Ion cells, which you're unlikely to encounter inside a camera, keep the vinegar or other acid on the weak side because of the slight risk of fireworks. The electrolyte can wick up wires, and the cleaning process WILL wick up wires, so you really want to ensure you've neutralized everything if you don't intend to replace or re-trim affected wires.
 
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Andreas Thaler

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Thanks!
 
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Andreas Thaler

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Battery Electrolyte Victim #1: The revenge of the forgotten batteries





The external condition does not inspire much hope, the stuck battery holder suggests that four batteries have taken revenge for having been forgotten in the camera for years.




It looks better here.




The leatherette has become rotten due to the leaked electrolyte and falls apart when you try to remove it.








The retaining ring has become a molded unit with the tripod thread. I drill the two holes so that I can attach the spanner wrench. But no chance, the ring doesn't move.




This screw no longer offers a hold for the screwdriver, and it cannot be drilled deep enough to use a screw extractor.

Since the batteries are still inserted, I can't get to the two screws that hold the battery compartment underneath.




The battery holder has to come out so that I can remove the battery compartment.

My screwdriver for rough work once again proves its worth as a lever.








Now I can unscrew the battery compartment, except for one screw, and I don't have to use much force. I can also remove the tripod thread and the seized mounting plate.




The connectors for the cables are rotten.




Unsoldered
 
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Andreas Thaler

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Toxic waste




One of the connections on the purple electrolytic capacitor is corroded. I can't tell for sure whether this is coming from the battery or whether the capacitor is losing electrolyte. It definitely needs to be replaced.

The soldering points to the right of the capacitor also need to be replaced; they are corroded too.








I remove the circuit board.

It would be best if I replaced the whole thing.




The inside of the front panel is probably coated with a layer of copper. Ideal for the vapors from the battery electrolyte. Total corrosion.







Contamination, the mechanism for stop down is seized.




It looks good on the upper board.




A sad picture.
 
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Andreas Thaler

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Assessment
  • This T90 shows what forgotten batteries can do to a device over time.
  • Anyway I have original spare parts for everything from my abandoned T90s.
  • The question is whether the considerable work for a repair makes sense. I assume that the battery electrolyte is also causing trouble in places that are not visible and that this is affecting functions or causing them to fail.
  • The crucial question is whether the two shutter magnets are still working. I can only test this when I trigger the camera. And for that, it has to be restored.
  • If the magnets don't work, which happens with T90s that have been left lying around for a long time, all the work was in vain. Because they are not accessible to me deep in the camera.
I think it's better to put this electrolyte corpse with the spare parts, in a well-sealed plastic bag.

What do you think?
 
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BrianShaw

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Bushcat said:
... The electrolyte can wick up wires, and the cleaning process WILL wick up wires, so you really want to ensure you've neutralized everything if you don't intend to replace or re-trim affected wires.
Click to expand...

Black wire syndrome. Just yesterday I experienced that for the first time in a light meter. Cleaning and re-trim didn't work out as an option. Replacement seems to be the only way to go.
 
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Andreas Thaler

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If you want to do it seriously, the camera would have to be disassembled and cleaned.

What that means in the case of a T90 is clear.
 
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Andreas Thaler

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I use descaling solution for coffee machines (Durgol). It works well.
 
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Andreas Thaler

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Rechargeable Nickel Metal Hydride batteries have been in the T90.

What are the cleaning options here?
 
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Andreas Thaler

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koraks said:
Like my father always used to see: "sleep on it". Don't rush/force a decision. There's no hurry. Set it aside for some time, then decide where to go.
Click to expand...

I've thought about it, I'll do it.

I'm taking the spare parts from the T90, which I recently made inoperable. In the best case scenario, part of it will live on.

In any case, it's good exercise.
 
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Andreas Thaler

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Canon T90 restored from total loss

Today I tackled the first electrolytic corpse.

I actually didn't want to put any work into it because I didn't think it would work. The leaking batteries had wreaked havoc inside the camera.

But since I'm not going to avoid any more repair challenges in order to improve myself, I got to work after breakfast.

My plan was as follows:
  • Remove spare parts from an abandoned T90: circuit board with electrolytic capacitor, battery compartment, tripod thread and front panel.
  • Replace these parts on the repair candidate.
  • Internal and external cleaning as well as possible.
Here is the report.




Removing the tripod thread, to do this I first removed the battery compartment.




Desoldering and removing the small circuit board. There are many cables in a small space, which makes soldering difficult.




The mechanism for manually stopping down the lens is no longer functional due to the vaporization of the leaked battery electrolyte.








Using Durgol descaling solution and distilled water I can make the mechanism move again.




Inserting the replacement board.

It must first be soldered to a flexible board and then fitted under a wiring harness.




I had to shorten the yellow cable because the electrolyte had attacked it. Therefore, a bridge had to be made to the soldering point.




The installation is complete, all cables from the camera are connected to the circuit board.




Now I can solder the replacement battery compartment to the circuit boards.




It will be exciting, a first test with inserted batteries - yes, the LCD shows that the T90 has power again!




Since, as expected, the mirror did not trigger and an arrow flashed on the display, I also cleaned the contact surfaces of the mirror magnet on this T90.

Now we’ll see if this T90 can be saved.

Does the shutter release after installing the mirror magnet? Or do the two shutter magnets, which I cannot reach deep inside the camera, also need cleaning?

Hurray, the shutter works!




This is followed by cleaning with Durgol and distilled water. Electrolyte residues are difficult to remove or have to be scraped off.




The T90 is reassembled.

I clean the plastic casing with isopropyl alcohol.

The front panel, the rubber grip and the leatherette on the bottom are still missing.
 
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Andreas Thaler

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Before I attach the replacement front plate, I lubricate the mechanism of the stop down mechanism with Ballistol universal oil, which I had previously cleaned.




Half a day of work that was worth it.




This camera life could be saved and goes on


+++

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

koraks

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Watch out:

This solder joint doesn't look good. The upper piece of wire didn't wet properly with solder.
I'd also insulate the joint with a piece of shrink wrap.
 
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Andreas Thaler

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koraks said:
Watch out:
View attachment 375071
This solder joint doesn't look good. The upper piece of wire didn't wet properly with solder.
I'd also insulate the joint with a piece of shrink wrap.
Click to expand...

Yes, that's what it says in the textbook, but this is the reality.

And that's with electronics that are decades old, cables that - like here - are no longer in perfect condition and solder joints on circuit boards where you're lucky if you can still solder anything at all.

It's important that the solder joint is sufficiently strong and conducts properly. It's not cold because the solder runs and it doesn't matter if part of the connecting wire is exposed.

The insulation of the jumper wire bridge is dimensioned so that it is insulated where it is necessary. Nothing moves here and all possible contact points are far away.

You will rarely achieve textbook-like soldering in camera repairs
 
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