Problem with 420EX

[hecya]

After several months of moderate use my flash is having a strange behaviour. It fires but the image is well underexposed. With the built in flash the results are fine so my guess ia that the metering on the camera is fine.

I tested with the flash on and off on M mode with the same aperture and speed and the results are identical even when the flash fires so I guess that the firing is too early or too late. The green lamp on the flash never turns on after the exposure. In auto mode the results with the 420EX are very dark. It looks as if the exposure is about 2 stops underexposed.

I have changed batteries on the flash and recharged the battery on the 20D. I also reverted to factory parameters.

Have any of you suffered the same problem?

[scottbergerphoto]

A 420EX is getting a little long in the tooth. It may need a new capacitor or to have the one inside reconditioned. There are notes on this in the Flash Bible in the FAQ.

[hecya]

After eading the flash info I set to second curtain sync and tried the flash in manual mode. The same problem. So I decided to use a long exposure, 3 secs, and then I noticed that only fires the preflash burst of light and not the main one. Only when I tested at 10 secs, the flash fired twice.
So I guess that the problem is that the flash takes too long to recharge even when the preflash is a low power output. Also when firing it manually with the pilot button, the indicator never goes green so I guess also that the power output is lower. The flash is still dead but at least I know a bit more of the cause.

[cdifoto]

Lame suggestion perhaps...but have you tried new batteries? Sounds like it just doesn't have enough juice...

[TheSteveMadden]

Have you tried cleaning the hot shoe and flash shoe contacts? They might be dirty and intermittantly not sending ETTL/flash commands.