R4A Open Flash Circuit?

[Leigh Youdale]

Has anyone had this problem? I rarely use flash but yesterday at Christmas lunch I plugged my flash into the R4A and found that a couple of seconds after charging up each time it self-triggered. It doesn't happen on the R3A so I suspect the flash circuit must be permanently open or there's a faulty contact inside the camera that allows the contacts to close and trigger the flash once the charge reaches a certain level.

 

[payasam]

Circuit problem, clearly.

 

[Dwig]

...I suspect the flash circuit must be permanently open ...

That would be "permanently closed" not "open". With a permanently open circuit, the flash would never fire.

Presuming you checked it out both with a cocked and uncocked shutter and, assuming by "plugged in" you are inferring the use of a sync cord rather than hot shoe, with no accessory (e.g. finder) in the shoe then it would seem that there is some issue with the shutter system. I'm not intimate with the internal workings of the Bessa electronic shutters, but many such beasts don't use mechanical contacts to trigger the flash. They use an electronic "switch" controlled by the timing circuits that control the shutter triggering the flash at a fixed time after it releases the first shutter curtain.

 

[Leigh Youdale]

That would be "permanently closed" not "open". With a permanently open circuit, the flash would never fire.

Presuming you checked it out both with a cocked and uncocked shutter and, assuming by "plugged in" you are inferring the use of a sync cord rather than hot shoe, with no accessory (e.g. finder) in the shoe then it would seem that there is some issue with the shutter system. I'm not intimate with the internal workings of the Bessa electronic shutters, but many such beasts don't use mechanical contacts to trigger the flash. They use an electronic "switch" controlled by the timing circuits that control the shutter triggering the flash at a fixed time after it releases the first shutter curtain.

Well, semantics perhaps. Technically correct but it's not the way we use the term for aircraft magnetos! If you've got an open circuit on a magneto, the prop is considered "live". i.e. Don't touch it!

Cocked or uncocked makes no difference. Hot shoe or sync cord makes no difference. I'm pretty sure it's either a faulty contact or maybe a PCB issue. I don't know what's inside the Bessa but it does have an electronic shutter. What I find a little curious is that the discharge of the flash unit does not take place immediately the "fully charged" indicator light comes on (when in normal operation you could release the shutter and the flash operates) but there is a delay of a few seconds before the flash discharges. It's almost as if it has to go on building the charge in the capacitor to a higher level and then there is a flashover or some other circumstance that allows the discharge to take place - and it keeps on doing this without touching the camera until you remove or turn off the flash unit.

 

[monopix]

Would be worth trying another flash. It might just be an incompatibility rather than an actual fault - especially if the flash is quite old. It may be the voltage is too high for the camera and it's causing a breakdown in the circuit once the voltage reaches the critical point. Modern flashes have quite low voltages on the camera connection and many new cameras can't cope with the high voltages of the older flashes.