Why is my Canon 155A Speedlite not firing from the hotshoe of my Canon AE-1?

Question

The AE-1's hotshoe won't fire the flash from some reason. I have the shutter speed set to 1/60s and my aperture is set to A (auto). The test button on the 155A fires the flash as does shorting two of the hot shoe connectors, but the shutter button won't for whatever reason. I can see that the camera senses the the flash because the light meter is locked on the appropriate f-stop. But I have no luck getting it to fire the flash. Using the sync port on a different, non-hotshoe flash unit works but I have no way of testing a sync port on the 155A. I've also tried cleaning the hot shoe connections.

Any help would be appreciated.

Answer 1

I had this exact same problem with a Canon AE-1 + Speedlite 155A—it would power up and flash via the test button but was never triggered by the camera—and solved it yesterday:

By removing the four tiny screws around the hot shoe connector, you can split the case on the Speedlite flash unit. Very quickly, I noticed that, of the several tiny wires that snake into the hot shoe connector, the yellow wire was split/broken. I was able to strip about 1/16" of wire on either end of the break, solder it, and then wrap it with a tiny piece of electrical tape. Once I managed to get the sides of the case back together and everything buttoned up, the flash unit began working correctly again and was automatically triggered by the AE-1.

NOTE: it is quite difficult to get the flash unit back together, once the various components have been bumped around. Can be done, obviously, but takes quite a bit of time and lots of patience to reassemble, especially without damaging any wires or connections in the process.