Two Canon EFs not working: Damage to the power supply caused by battery electrolyte [repaired both]

Andreas Thaler said:

Thank you!

But the first EF also has to come back to life.

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I'm not yet completely clear on how the positive connections in the battery holder make contact with the batteries.

So I'll check where voltage can be measured on the Weincell battery and how the contact is made in the battery holder. Then I can start troubleshooting.

A third cable (brown) is connected in the middle of the series connection of the batteries. I'll find out what it's doing there.

The Nat Cam Service Manual for the EF contains circuit diagrams and test procedures.

I'm optimistic that it's a problem in the power supply area, i.e. where I worked. That corresponds to the fault pattern on the second EF.

When I can measure the operating voltage on the battery holder I know that my pliers epoxy contact project works.

Andreas Thaler said:

Do you have any further information about this? I'm very interested.

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To do any soldering on those lugs, you'll have to separate them from the plastic battery housing to begin with. Even copper soldering would be too hot and would cause damage to the plastic holder. Soldering stainless would involve much higher temperatures, totally frying the plastic part.

koraks said:

To do any soldering on those lugs, you'll have to separate them from the plastic battery housing to begin with. Even copper soldering would be too hot and would cause damage to the plastic holder. Soldering stainless would involve much higher temperatures, totally frying the plastic part.

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I removed the contacts, but it didn't work even at 400 degrees Celsius (752 F) and lead-containing solder.

A higher temperature will just boil the solder.

That would be hard soldering, and I'm not equipped for that.

No lasting success with pliers and epoxy



Unfortunately, connecting the cable ends to metal contacts by pressing them together with pliers and fixing them with epoxy did not result in a permanently stable electrical connection.

When checking the connections on the battery holder again for continuity, loose contacts or no connection were found.

This method is therefore out of the question.

So I attribute the problems with the power supply to the defective battery holder.


Other options

Since soldering is not working, I could try using Electric Paint again. However, I have concerns about the mechanical strength challenged by cable pressure and the slight resistance of the material, which can affect the output voltage of the battery holder.

This also applies to Wire Glue mentioned by @4season, which I will definitely take a look at if I can find it. Thanks again for the tip!

I could also try to bridge the contacts in the battery holder with a self-adhesive copper conductor and cables, but that would be a lot of tinkering that I don't feel like doing.

The only option left is a battery holder from a Canon EF for spare parts, which I might come across one day.

Structure of the Canon EF battery holder

It took me some time to understand how the current flows in the battery holder. As is usually the case, it is not that simple




The blue arrow points to the negative connection (blue cable on the circuit board), the orange arrow to the positive connection (orange cable).

There should be a voltage of 2.70 volts here (2 x 1.35 V Weincell batteries).

The spiral-shaped contact on the right is for the negative pole of the right battery, the ring-shaped contact all around is for the positive connection.

The ring-shaped contact on the right is connected to the spiral-shaped one on the left (green arrow).

The latter forms the connection for the negative pole of the left battery and the ring-shaped one all around for the positive pole.

So the batteries are connected in series as usual. This means that the operating voltage is derived from the sum of the individual voltages of the batteries.


To better understand this system

you have to look at the Weincell battery (replacement for PX 625 mercury battery) and its electrical poles.




The negative pole is inside the green circle.




The rest of the housing (except for a narrow ring as an insulator) is positive.




Here you can see that the edge of the battery connects to the ring-shaped contact for plus.

The spring in the battery chamber cover obviously only has the task of pressing the battery against the contacts, but no electrical function.




This is where the cables for the negative connection (blue) and the positive connection (orange) are attached.

A third cable (brown) - is on the bottom where the two batteries connect.








The batteries are inserted with the positive pole facing upwards.

This metal frame fixes the battery holder with two screws and has threads for the two battery chamber covers.

The base plate, which is installed between the battery chamber and the battery chamber covers, is still missing here.


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

So if anyone has a Canon EF for spare parts with an intact battery compartment, please let me know!

Andreas Thaler said:

Do you have any further information about this? I'm very interested.

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I have never tried it, but it involves the use of an acidic flux:

https://www.wikihow.com/Solder-Stainless-Steel

Personally, I'd want to try Wire Glue first.

Andreas Thaler said:

Canon EF number two: A new day, a new game

Battery electrolyte also destroyed solder connections in the second EF without any visible contamination in the battery chamber.


[…]


View attachment 381867

The new cable is installed, the epoxy is now hardening.

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This connection with pliers/epoxy on the second EF holds.

If that changes, I bridge the contact with copper foil and a bit of soldering.

Excellent work! No such thing as failure only negative results!

mshchem said:

Excellent work! No such thing as failure only negative results!

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Thanks!

If I go through all my options until there are none left, I can finish work on a project.

Besides, no one else will take on repairs like this. „No parts“ is the usual response from repair shops. And in this case, it's even true

Andreas Thaler said:

So if anyone has a Canon EF for spare parts with an intact battery compartment, please let me know!

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Currently, the cheapest Canon EF for spare parts that I can find on eBay with reasonable shipping costs are EUR 80 (USD 86).

But it remains uncertain whether the battery holder is in good condition as a spare part.

The seller would have to remove it and check it, and I don't think anyone would do that.

I found an EF for spare parts.

At a reasonable price and I have already had very good experiences with the Finnish store:


It remains to be seen whether the battery holder is OK, so it remains exciting.

Just incidental to seeing your soldering work, do you have a range of solders available? Something with 4% silver (Sn96/Ag4) might be worth trying on anything you think is a type or steel ot otherwise non-solderable. Also, if you can get the "non-solderable" item off the camera, you can always strip off the plating, and replate it with something you know will work. A small plastic container, a battery (I use a constant-current power source simply because I have one), chemicals and a host elctrode followed by donor electrode (a bit of nickel, say) would get the job done.

Bushcat said:

Just incidental to seeing your soldering work, do you have a range of solders available? Something with 4% silver (Sn96/Ag4) might be worth trying on anything you think is a type or steel ot otherwise non-solderable.

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Thanks, I also have lead free solder that I will try.

Bushcat said:

Also, if you can get the "non-solderable" item off the camera, you can always strip off the plating, and replate it with something you know will work. A small plastic container, a battery (I use a constant-current power source simply because I have one), chemicals and a host elctrode followed by donor electrode (a bit of nickel, say) would get the job done.

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Can you explain this setup in more detail?

Quick comment about lead-free solder: that's not an alternative to the solder I mentioned.

Disclaimer: in principal, it's all simple stuff but sometimes you're doing simple stuff with some pretty iffy chemicals. So this is what I may or may not do below, but you must do your own research and decide whether these chemicals are the kind of thing you want to play with. In particular, if you are removing chrome chemically or electrically, please don't experiment with different chemicals! Also, you need to understand and be comfortable working with any acids and lye.

The deplating side is your choice of removal methods, either mechanical or chemical. I prefer just rubbing/abrading stuff down: I figure I'm not trying to remove everything, I'm just trying to create a patch that will take solder. Some of the chemicals can be a bit iffy depending on what you're removing. Chrome, for example, would need something like 30% hydrochloric acid, or maybe sodium hydroxide but you don't want that anywhere near aluminum. Soak, agitate occasionally, take your time. Wear gloves, goggles, clothing you don't like, etc. You could also reverse the electroplating process but the starting chemicals and waste byproducts are very, very iffy for things like chrome so I'll leave that to your own research. Disposal is probably heavily regulated in your location.

Electroplating is easy, in comparison: put the item you want to plate in a sturdy plastic container. You'll need a nickel electrode and an electrolyte: nickel acetate. You can buy this or make it. You'll be using a nickel electrode during the plating process anyway, so you may as well make your own as part of the learning process. To make, put standard 5% white/industrial/pharmaceutical vinegar (not chip buttie vinegar) in a jar, add a pinch of salt to ensure conductivity. Put two nickel electrodes in, wire them up to your power supply, set it to maybe 3V, and watch for bubbles on one electrode. You want low voltage, low current, and you're aiming for a clear, lightish green solution after an hour or two. This is your electrolyte. If it happens too quickly, the current is too high. If it's cloudy or any color other than lightish green, the nickel is contaminated with other metals and isn't suitable for either making the electrolyte or, indeed, electroplating so in that sense it's a good test.

So, to plate: wire the object to the negative side. One nickel electrode to the positive side. Turn it on, and watch for little bubbles. You want everything to take time, nothing to get more than barely warm, say. With a little container you can use surprisingly low voltage and current: if you don't have a power supply, one or two alkaline cells might be OK, relying on their internal resistance to limit current if the electrolyte is too conductive (i.e. too much salt).

(Some metals won't take the nickel. These, you can copper-plate first: Google is your friend. Beware, copper acetate is a bit of a bugger.)

Finally, if you've got the nickel coating thick and nice enough, it will only need a little chemical cleaning or a rub when you come to solder it. But, if you find you enjoy plating stuff, and you won't be soldering for a month or two, you can finish off with a very thin gold plating: it doesn't have to look gold. When you do decide to solder, the gold will dissolve and you'll be soldering onto the nickel.

FINALLY, there are plating pens which come prefilled with everything you need to start plating, but they're not cheap. You simply plug them in and rub them on the item. But you'll be rubbing a long time to get a solderable surface.

@Bushcat Thank you!

Andreas Thaler said:

Thanks, I also have lead free solder that I will try.

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FWIW: I have a strong dislike for lead-free solder. Poor wetting properties. Dull appearance. Higher melting point, with potential damage to insulators when hand soldering. Obviously OK for wave soldering, but that is not what we are discussing here. An opinion shared by the professional electronicians at my previous university lab: they only stock and use "real" solder.

Just to follow up on bernard_L and my own post, in general I'd think lead-free solder is never the solution to any of life's problems but it seems I'm behind the times because, having said that, SAC solders do contain silver, and something like SAC405 is 4% silver, right in the ballpark for stainless steel. Also, SAC is eutectic: it melts nicely at under 220C. So, that might make a wire-to-stainless joint but I've never used it for that. But the silver bumps the cost up, so a generic unlabelled lead-free solder is likely to use nickel instead of silver, which won't work on steel (though great on our recently nickel-plated item). Anyway, now I've nicely clouded the issue, I'll move on. But when I was paid to use solder, lead-free wasn't allowed near military or medical equipment because it made brittle joints. Or rather, the mechanism of its brittleness was not fully understood.

Also this Canon EF could be repaired finally

Today the Canon EF for spare parts arrived from Finland.






The outside of the housing shows some wear, otherwise I have not tested the camera.

Since my repair candidate is in mint condition, this EF will have to give up its battery compartment.




An exciting moment.

Are the connections on the battery compartment OK and not corroded by battery electrolyte?

Everything is in good condition, excellent!




In order to keep all three cables soldered and avoid any problems when re-soldering, I separated the brown cable with the side cutter.

I cannot reach its second connection in the camera with the tip of the soldering iron.




The connections of the orange and blue cables can be easily desoldered from the circuit board.




I use the wire stripper to remove a piece of the insulation so that I can tin the cable.

This is tricky because the cable is short, thin and I can't put any strain on its fragile soldering point.




The cable end is now tinned and ready to be soldered to its counterpart in the camera.




The connection cable, which I was able to solder to the circuit board with a sleeve deep in the camera, gets an extension.




Both cable ends are soldered and covered with insulation tape. I didn't want to use shrink tubing here to keep heat away from this sensitive area.




The battery holder is connected to the circuit board.

Since the solder connections for the blue and orange cables had come loose, I used the Dremel Stylo to open up spots on the circuit board in order to create new solder connections.




As the battery control LED did not light up during the first test and the measuring needle in the viewfinder did not react plausibly, I removed the battery compartment.

I checked all connections for continuity and checked the visible part of the circuit board and component connections for damage or short circuits. I found nothing unusual.


Success

After reassembly, another test was carried out and now the LED and light meter were working.

A relief!

There was probably a contact problem, but I don't know where.

I didn't have any other sensible options for checking the circuit. The circuit board is glued to the housing here and to see more, I would have had to take the camera apart.

But because of the repair of the other EF, I was convinced that the problem was only around the battery compartment.




Now in a good mood, I used some Ballistol universal oil to make it easier to screw in the two battery chamber covers.




One last check before I put the base plate on.




This EF is also back among the living




The project has been successfully completed.

Both mint Canon EF could be saved.

The third EF remains for spare parts.


+++

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

Andreas Thaler said:

The third EF remains for spare parts.

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It becomes a project camera.

bernard_L said:

It becomes a project camera.

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No no no!!

I had a hard time soldering wires to battery contacts until I got some proper flux. I'm not a soldering expert but sometimes you need a more active flux in order to remove the surface oxidation and get the two metals to bond. Or something like that.

vandergus said:

I had a hard time soldering wires to battery contacts until I got some proper flux. I'm not a soldering expert but sometimes you need a more active flux in order to remove the surface oxidation and get the two metals to bond. Or something like that.

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Maybe electric welding will work?

Andreas Thaler said:

Maybe electric welding will work?

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No, good flux was enough to enable soldering.

Andreas Thaler said:

This connection with pliers/epoxy on the second EF holds.

If that changes, I bridge the contact with copper foil and a bit of soldering.

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The electrical connection, fixed with epoxy, obviously didn't hold, so I'll continue. Thankfully it's only one connection on the battery holder that I need to fix.

More on that soon.