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

[Andreas Thaler]

I have had two two beautiful Canon EFs for many years.

They have been working, but the battery control LED on one of them wouldn't come on. I didn't think anything of it, and when I started repairing, I wanted to take a look at the problem.

Today I fitted both with 1.35 volt Weincell batteries and tested them.

The control LEDs on both remained dead, but the needles on the light meters didn't move either, only a little in bulb mode.

Considerations

• Two cameras of the same type that have the same problems after a long time.
• In both cases, the battery control LEDs, which are positioned in the circuit near the batteries, do not light up. Here is the circuit diagram for this area1:

One or more of the electronic components listed here could be defective, but I can rule out the possibility that they would break down on their own over time, especially in two cases.

• The only thing left is oxidation/corrosion, which is probably the most common problem when SLRs fail.

So I cleaned the battery contacts with electronics cleaner, polished them with the hard rubber attachment on the Dremel Stylo, and when that didn't help …

… I took off the base plates.

Here everything still looks inconspicuous except for corrosion on the contact of the battery indicator LED.

I have already removed one screw from the battery compartment and loosened the second one.

When I carefully lifted out the battery compartment, it was immediately clear why this EF was not functioning:

Leaked battery electrolyte had destroyed the soldering points of cables to the battery compartment, which were now without a connection.

The electrolyte remains liquid on the circuit board, and where it can react with metal it causes corrosion.

The two-part battery compartment.

The second EF looks similar.


Repair

To repair the damage to both cameras, I will proceed as follows:

• Check how far the electrolyte has penetrated into the cameras.
• Clean the affected area of electrolyte.
• Remove and renew the corroded solder joints and replace the contaminated cables that serve as bridges for the electrolyte.

So some cleaning and soldering work, which will hopefully be successful.

We'll continue soon.

---

Canon EF camera - Wikipedia

en.m.wikipedia.org

1

Canon EF Service Guide

National Camera Repair Guide

learncamerarepair.com

 

[loccdor]

Thank you for sharing your repair. It's a bit confusing that the Canon EF camera and the Canon EF lens mount are two very different things. At first I thought you were talking about their autofocus SLRs.

 

[bernard_L]

How inappropriate that your post re-activates my GAS for a Black Beauty.

 

[koraks]

Keep an eye on these guys. They look like tantalum electrolytic capacitors. Given their age, they're virtually guaranteed to leak pretty badly.

 

[Andreas Thaler]

Repair

The contact for the battery control LED is corroded, but I can't remove it for cleaning because I can't get the screw out of the flexible circuit board.

The trim potentiometers are protected with transparent covers. I am not allowed to adjust anything here, these are the factory settings.

The bottom of the contact.

Below the two trim potentiometers is the counter contact for the battery control LED, which also needs to be cleaned.

I use the hard rubber tip on the Dremel Stylo to remove the corrosion.

Almost turned to gold.

The counter contact under the potentiometers turned to silver after polishing

Where I can't reach with the Dremel, I remove the deposits with Durgol descaler and Aqua purificata. Unfortunately, I can't get under the plastic washers around the screw with this.

The battery holder with the three corroded soldering points is bathed in Durgol.

The circuit board is free of liquid electrolyte according to Durgol and Aqua Purificata.

The contaminated cables have been desoldered and the cable ends of the new ones are currently being tinned.

The new cables are on board. I can't replace the brown one because its connection on the circuit board is too deep in the housing. But the soldering point looks good.

The battery holder with solder joints corroded by battery electrolyte after the bath in Durgol and subsequent rinsing with water.

Using the Dremel Stylo and a small ball-end cutter, I remove almost any corroded solder.

This loosens this contact, which I then glue back on with Pliobond.

Unfortunately, I can't replace the previously removed soldering points because the metal doesn't accept solder.

So all I can do is experiment with Electric Paint, which I use to connect the wire ends to the contacts.

This now has to harden overnight and if it holds, I'll use it to attach the orange cable.

According to the manufacturer, electric paint can be loaded with up to 12 volts or 50 mA.

The operating voltage is 2 * 1.35 volts, which is fine. I don't think that more than 50 mA flows through the circuit, but I don't have any information on that.

The tube with Electric Paint is long past its expiration date, I'll see what happens.

 

[Andreas Thaler]

View attachment 381718
Keep an eye on these guys. They look like tantalum electrolytic capacitors. Given their age, they're virtually guaranteed to leak pretty badly.

Thanks!

I'll see if I can get the power supply working and then think about what else I can do.

 

[Andreas Thaler]

How inappropriate that your post re-activates my GAS for a Black Beauty.

Yes, but you see what care the beauty needs when she has been treated badly

 

[Andreas Thaler]

Thank you for sharing your repair. It's a bit confusing that the Canon EF camera and the Canon EF lens mount are two very different things. At first I thought you were talking about their autofocus SLRs.

If I should manage to finish this successfully, I'm thinking about trying an EOS. But I won't report on the expected disaster here

 

[Kodachromeguy]

Thanks for the interesting summary and photographs. Many of the LeicaMeter MR-4 meters suffer from the same propagating corrosion. The battery compartment may look clean, but the wiring behind is a mess.

EF question: are they generally usable now, or is battery leakage widespread?

 

[ic-racer]

This reminded me of what happend to my Yamaha M-45 Power Amplifier. There is a common fault with the glue used to hold the capacitors in place. The deteriorating glue damages the components. In this case a resistor went open circuit.

Before:

After:

 

[Andreas Thaler]

I thought this would be an easy tour...

More on that tomorrow, I'm going to sleep.

 

[Andreas Thaler]

Second attempt with epoxy

Finally I wasn't convinced by the idea of using electric paint to connect the cables to the battery holder.

I was particularly concerned about the mechanical stress on the adhesive points with the stiff jumper wire that I had available.

The wire can be bent when fitting the battery holder into the camera, but it still presses against the adhesive points. I haven't yet discovered the fine, flexible wires used by camera manufacturers as new goods.

So I wanted to try using epoxy, which is much more resistant but doesn't conduct electricity.

In order to connect the cables to the terminal lugs in an electrically conductive manner, I bent the wire ends into eyelets, which I then squeezed onto the terminal lugs with pliers.

To fix it, I put a drop of epoxy on it.

In order to do this, I had to disassemble the battery holder.

Connecting the cables to the battery holder terminals with pliers and epoxy.

Heating the epoxy compounds for faster curing with the Dremel Versatip butane gas burner.

Checking the connections for continuity.

My patient wife took the photo

The reassembled battery holder with cables, ready for installation.


Cable soldering deep in the housing

The third cable to the battery holder has come off. It is connected to the circuit board inside the housing.

It is too deep to reach the soldering point in a controlled manner with the soldering tips I have available. To get there, I would have had to disassemble the camera.

This brown cable was also contaminated by battery electrolyte, which had obviously damaged the soldering point in the camera.

So I thought about how I could solder in a new cable.

If I build some kind of sleeve that fixes the new cable to the soldering point, it should work.

I drilled a hole the size of the soldering point on the circuit board into a piece of self-adhesive copper conductor. I then soldered the new cable onto it using plenty of solder.

There is now a larger solder joint on the underside of the copper conductor, which I had to connect to the solder joint in the camera.

To do this, I placed the self-adhesive strip on the camera's circuit board so that both soldering points covered each other.

With the soldering tip I heated the solder on the top of the copper strip and connected the new cable this way.

Since I had applied plenty of solder to the top of the strip, the soldering worked without sight.


A lot of work but no success

After hours of work, the battery holder was reinstalled with new cables.

Unfortunately, I was unable to restore the power supply.

So I removed the battery holder again to check everything.

In the process, a solder joint corroded by battery electrolyte on the circuit board came off completely. No way to solder it back on.

That's when I gave up.

 

[koraks]

In the process, a solder joint corroded by battery electrolyte on the circuit board came off completely. No way to solder it back on.

You could track down the connecting trace to the next point with a solder joint and then see if you can run a wire parallel to it to that point.

 

[Andreas Thaler]

Conclusion

• A lot of work that didn't bring any success, but instead developed new repair techniques.
• With pliers and epoxy, stable conductive connections can be made when soldering is not possible.
• I don't know how Canon managed to put soldering points on the contacts in the battery holder.
• Once again, it shows the damage that leaked battery electrolyte can cause. From the outside, there was no contamination visible in the battery holders of either camera. Over the years, the electrolyte destroyed soldering points, spreading across the plastic-insulated cables. Such soldering connections have to be replaced, which is often difficult or even impossible.
• Let's see how it goes with the second Canon EF - the problems are the same.

+++

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

 

[Andreas Thaler]

You could track down the connecting trace to the next point with a solder joint and then see if you can run a wire parallel to it to that point.

Good idea, it's the blue cable in the picture above.

I'll expose the corresponding conductor track on the flexible board under the old soldering point and place a new soldering point.

But that's just for practice.

 

[koraks]

I'll expose the corresponding conductor track on the flexible board under the old soldering point and place a new soldering point.

This may work, too. Try to keep heat as low and brief as possible to prevent the copper layer from peeling away from the flex board.

 

[Andreas Thaler]

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.

The camera had worked for years until connections were broken.

Without anyone knowing about the silent chemical destruction in the camera

Here, two of the three soldering points on the battery holder are damaged by corrosion. The blue cable has come off.

The soldering point of the blue cable on the circuit board is also damaged.

The electrolyte residue around the screw at the bottom has not caused any damage.

The flexible circuit board is resistant to electrolyte.

Based on my previous experience with the soldering points on the battery holder contacts on the EF, I try to preserve them. I use the probe to scratch off the surface.

I use the Dremel to remove solder in the hope that the rest is still solderable, which unfortunately isn't the case.

So I remove all the solder on the contact below and then reattach the new cable with pliers and epoxy.

The contact in the middle can still be soldered, the third one is fine.

I cleaned up here.

I should actually redo this soldering point as well, as the old solder is contaminated with electrolyte. But I don't want to get involved in that now.

The soldering point still looks good after having removed some of the old solder.

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

 

[Andreas Thaler]

All three cables are connected to the battery compartment and the circuit board.

Two Weincell batteries for the first test with the base plate still removed.

First, test the battery control LED, which is located on the top of the EF, the red test button is located on the bottom.

The LED flashes, voltage is there!

Looking through the viewfinder without a lens. The light meter is working.

Even with the lens attached, everything seems plausible, shutter priority works.

Back Among the Living

 

[Andreas Thaler]

Conclusion

• This repair was relatively easy, and the experience I had with the first Canon EF helped.
• The method of connecting two electrical contacts with pliers and epoxy has proven itself.
• In future, I will try to preserve solder joints in similar cases. The method that Canon used to attach the solder joints to the battery holder contacts will probably remain their secret.

---

The first Canon EF will be back on the table for a second repair attempt.

But now it's time for a break and the desk needs to be tidied up

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+++

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

 

[Andreas Thaler]

This reminded me of what happend to my Yamaha M-45 Power Amplifier. There is a common fault with the glue used to hold the capacitors in place. The deteriorating glue damages the components. In this case a resistor went open circuit.

Before:

View attachment 381816

After:
View attachment 381817

A clear warranty case!

 

[Andreas Thaler]

EF question: are they generally usable now, or is battery leakage widespread?

I think the batteries were forgotten in these two EFs.

The previous owners were probably able to remove the leaked battery electrolyte before it attacked the contacts in the battery holder. First, the electrolyte is liquid and can be removed with water. But the rest of the stuff got into the camera without anyone noticing.

This can happen to any SLR.

A chemical time bomb

 

[koraks]

Nice job! Glad to see making a new pad for the blue wire worked.

 

[Andreas Thaler]

Thank you!

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

 

[4season]

I think Canon may have used stainless steel for some of their battery terminals, and there are special procedures and materials for soldering that. Alternatively, a product like Wire Glue may be worth a try:

https://surehold.com/adhesives/wire-glue/

 

[Andreas Thaler]

I think Canon may have used stainless steel for some of their battery terminals, and there are special procedures and materials for soldering that.

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

Alternatively, a product like Wire Glue may be worth a try:

https://surehold.com/adhesives/wire-glue/

Thanks!

I'll look into how I can get it.