Flash malfunction: flash or body?

[DanK]

I use an old Canon 430 EX II flash. It has worked fine for years. However, in recent months, it will sometimes malfunction when first turned on with freshly charged batteries. It will rapidly discharge several times, perhaps 5, in quick succession. after that, it generally works fine.

This got me worrying yesterday when it happened on my 5DIII, and all of the buttons on the back of the camera stopped working. I took the flash off, turned the camera off for a short time, and it was fine when I restarted it. It seems as though there was a surge from the flash.

To try to diagnose this, I have been swapping batteries and camera bodies. So far, it has not happened on my old body (50D), but it happens infrequently enough that I can't tell if that is coincidence. It takes a while to fully charge the batteries and try again, so it would be days to test it often. I know this is happening with Ansmann 2850 mA rechargeables, which I have been using for years. It has not happened today with Powerex 2700 mA rechargeables, but again, that could be coincidence.

I called Canon, but they said there is no easy way of knowing what is what. The fault is sufficiently infequent that they might not see it if I sent the body and flash in. The rep suggested that most likely, the only way to know would be to have a second flash malfunction on the 5DIII or keep trying to see whether the old one fails on the 50D.

I'm close to the point of buying another used flash just to figure this out, but I thought I would ask for opinions first. The only thing that seems clear to me is that the capacitor is discharging when it shouldn't. It seems to me that the fault could be with the flash, with the batteries (if they are over charging), or with the body. If it is the body, it is mystifying that this only happens when I first put the flash on. Once this happens once (or perhaps twice, I can't recall), the flash functions perfectly on that body.

Any suggestions?

Thanks

Dan

[inkista]

Just checking, but you wait until you've got the flash fully seated on the hotshoe before turning it on, yes?

[DanK]

Just checking, but you wait until you've got the flash fully seated on the hotshoe before turning it on, yes?

yup.

I just got a note from someone else suggesting an intermittent short, perhaps in the hinge (which gets a lot of flexing the way I use the flash). He included this:

While it is unlikely that the short is causing full cap voltage to discharge into the camera's circuitry (else you'd have a brick now instead of a 5D3), the normal circuitry voltage most likely fed back into the camera (bypassing the diode protection at some point) , causing the fault you experienced. You, my friend, are one lucky guy IMO.

That was the way I was leaning. i thought I might be penny wise and pound foolish repeatedly trying this on two bodies, when the flash is a 6-year-old $300 unit.

[Manfred M]

The other issue with aging electronics is "tin whiskers"; the amount of lead in solder has been reduced (health and safety reasons) and the amount of tin has increased (solder is mostly a mixture of lead and tin). Over time these wiskers grow and can (and do) cause shorts and other intermittancy problems, and as the Canon rep has told you; devilishly hard to diagnose on a repair bench.

I would try to borrow a flash and try it on the camera, and it the problem does not occur, I'd suggest the old flash should be trashed.

[DanK]

Thanks. A replacement flash is the next step. Hopefully, that will be the end of it. If it happens with a new flash, the body goes back to Canon. Fortunately, it is under warranty until November.

On the assumption that it is the flash, I'm counting myself lucky that I didn't turn my 5D3 into a brick.

Now I just have to decide what to buy. The 430 ex II is inferior to the larger ones in many respects, but it is superior in that it is smaller and lighter, which is nice for macro work in the field.