Lesson 1 Canon AE-1: Cleaning the Magnets
Lesson 1 Canon AE-1: Cleaning the Magnets
Often, when you use a Canon AE-1 after a long time and insert a new battery, you’ll notice that the shutter is stuck. This can obviously be caused by various factors, but one of the most common is undoubtedly dirt on the MG2 and MG3 magnets located on the bottom of the camera.
From *The Camera Craftsman* Manual:
- MG2 – Release Electromagnet
- Holds the armature locked during shutter cocking.
- When you press the shutter release button, the circuit discharges a capacitor through the MG2 coil.
- This pulse temporarily cancels the permanent magnetism.
- The armature is released, allowing the mirror and shutter to begin moving.
➡️ MG2 initiates the shutter release.
If MG2 malfunctions--> You press the button but nothing happens or the shutter remains stuck.
- MG3 – Second Curtain Electromagnet
After MG2 has initiated the shutter release:
- MG3 holds the second shutter curtain in place.
- The electronic circuit keeps it energized for the set duration (1 s, 1/60, 1/1000, etc.).
- When the electronic timer cuts off the power, MG3 releases the second shutter curtain, ending the exposure.
In practice:
➡️ MG3 determines the exposure duration.
If MG3 isn’t working:
* the second curtain fires immediately → incorrect exposure times;
* or it remains held → shutter stuck open.
FROM THE CAMERA CRAFTSMAN MANUAL:
First, check the mechanical release mechanism: simply use a screwdriver to push the MG2 armature toward the front of the camera. The shutter should fire.
If the shutter fires, you know there is no mechanical problem.
So the problem could be:
- a broken MG2 coil (open coil);
- or a faulty capacitor—that is, the capacitor that discharges current through the coil to neutralize the permanent magnet.
You can check both the coil and the capacitor at the same time.
Wind the shutter. Then use tweezers to short the negative terminal of the MG2 coil to ground (the edge of the camera body or the ground screw on the flexible circuit board).
The armature should detach from the MG2 core and release the mirror.
This test bypasses the electronic switch that normally sends the current pulse to the MG2 coil.
Remember that capacitor C47 (47 μF) is connected in series with the MG2 coil.
When the electronic switch closes, it allows capacitor C47 to discharge through the MG2 coil.
If shorting the switch does not release the shutter, check that power is reaching the flexible circuit board. Locate the red wire running from the flexible circuit to the MG3 solenoid. This red wire connects the flexible circuit to the positive terminal of the battery. When measuring the voltage between the red wire and ground, you should read the full battery voltage (approximately 6.35 V with no current draw). Similarly, you can check the voltage at each terminal of the MG2 solenoid. You should measure the full battery voltage at each terminal. If you find it, it means the coil is not open.
Now let’s assume that the short-circuit test does not trigger the shutter.
However, you have measured the correct voltage on the flexible circuit board.
At this point, the question remains as to whether the faulty component is:
- the coil;
- or the capacitor.
You can replace:
- the entire electromagnet;
- or capacitor C47, located at the bottom of the camera.
To check whether the magnets are functioning properly, test them with a multimeter.
MG2 has a resistance of around 95 ohms;
MG3 has a resistance of around 224 ohms.
If they don’t have the correct voltage or show zero voltage, there’s definitely a problem with the coil—the solution is to replace them.
If they’re working but the camera doesn't fire, try cleaning the contacts on the armature and magnets, because the armature might not be returning to its original position due to being stuck to the magnet by dirt that has accumulated over the years.
First, use a powerful air blower; then, make sure to wear LATEX GLOVES and proceed with PATIENCE AND CAREFULNESS—OTHERWISE, YOU’LL MAKE A MESS.
To disassemble the MG2, remove the two screws and the ground screw to lift it just enough to remove the plastic cover (be careful not to break it). Then use the air blower again, this time with isopropyl alcohol or lighter fluid to remove the dirt and grease that has solidified after years and years of sitting in our closet. (Or Dad’s closet.) After that, clean the plastic cover as well, and gently reassemble everything.
Then move on to the MG3… here too, just two simple screws… clean the contacts the same way and reassemble.
Insert a battery and test the camera. It doesn’t work? Well, I’m sorry for you, but not everything in life is that simple… there could be dozens of other problems.
You can test MG2 again by shorting it with tweezers between the positive terminal and ground. If the camera triggers this way, the problem isn’t with the magnets but with something else in the part above the camera…
A damaged flexible printed circuit board or who knows what…
If it doesn’t work when tested with tweezers, then the magnet’s resistor or capacitor C47 isn’t working. Buy a replacement part or another car :(
Remember that you can, of course, also measure the battery voltage across the wires connected to the MG3 magnet. One of the red wires comes directly from the battery compartment, so it’s useful to test it against ground (as well as the other red and black wires, also on MG3), and you should read the battery voltage. If you get a reading, the electrical connections are okay and the coil isn’t open. If you don’t get the correct voltage, maybe the red wire between the battery compartment and the magnet is connected incorrectly or the coil isn’t working.
Solution: replace the MG3.
That’s all for today—see you in the next episode. For advice and more, write in the comments or message me privately :)
Brian from BRIANCAMERAWORKS