Canon Quint
Last Christmas my Dad's wife Joann gave me a couple of old flash units as she knows I am into old cameras and what not. One of them is the Canon Quint.
The Quint takes 5 AG1 flash bulbs and fires each in sequence saving the need to reload after each photo. On the back is a small window that shows which flash will fire next indicated with a number 1 to 5. Unfortunately this was stuck at the number 3. With all AG1 bulbs loaded the flash fired on number 3 but the number did not advance. The subsequent shutter closure did not cause the flash to fire again. I had also read of another person who had a Quint described with the same problem.
Disappointed and not wanting to just reload on each flash I disassembled the unit to see if it could be repaired. (See comments section for help in disassembling that some helpful reader has contributed.) In the photo below is the view from the back with the case removed. The silver square on the right shows the window (with a 1 showing now). The black cylinder to the left of it is a solenoid. Below that is a white cylinder which is the 15v battery. On the upper left are 2 capacitors 100uF and 250uF.
The solenoid is actuated when the flash contacts are shorted by the camera's shutter mechanism. This fires the flash and the solenoid advances a switch to engage the next flash bulb and advances the mechanical counter. Because the solenoid takes a lot of current the 250uF capacitor is charged from the battery through a resistor and supplies the instant high current required by the solenoid. (The other capacitor supplies the high current for the flash.) The trouble was the capacitor no longer works and is probably dried out. This was verified by substituting the 100uF capacitor and actuating the shutter.
I bought a 220 uF capacitor as the closest match. Modern capacitors are smaller and despite being 35v rather than 15v it was much smaller than the original and so had to be soldered in place.
Comments
Some items to mention:
To disassemble the unit, you need to open the front lid. You will see two slotted screws, one on each side, under reflector. You need to remove the bulb cartridge to see them. Don't bother loosening the two smaller screws near the left hand corner, as they hold down the solenoid. The two screws that you remove are long, about 1 inch in length.
Remove the battery cover, and then push the battery compartment inwards. This will move the entire flash contact / reflector panel to the front of the unit. As you push inwards, the PC synch cable needs to be fed in to give it slack. Also, the red test button is likely to fall out, so be sure to catch it and not lose it.
Eventually you push the inner panel out, and the outer cover can be slid along the synch cord until it is fully out of the way. Now you have the item exposed as in your photographs.
I also found that it's not too critical to match the capacitor values.
I had a 470uF 25V can capacitor with radial leads at hand. I used some heat shrink tubing to insulate the exposed leads, then soldered the leads similar to what you show. Make sure the polarity is correct: positive goes near the outer wall, and negative is to the lead near the solenoid.
To prevent this higher value capacitor from affecting the RC time constant (original Canon values of 250uF with a 1K current limiting resistor make for t = 0.25 seconds), I soldered another 1K ohm resistor in parallel with the original load resistor. This is a small resistor marked "1K ohm", and the leads go from the positive battery terminal to the positive lead of the capacitor stack. I would have loved to put a diode in there to prevent damage to the capacitors if you put the battery in backwards, but the space is limited, and I didn't want to unsolder the original connections.
In my case, the large 250uF capacitor had leaked, and the terminal needed to be cleaned. The 150uF capacitor which is what actually fires the flash is in fine condition. I tested it to have 212 uF capacitance.
It is so gratifying to hear the solenoid clack when you finally get it all soldered up.
Again, thanks for your wonderful research work.