Rolleicord III flash PC contact weirdness

[Vonder]

My new-to-me Rolleicord III has an odd-to-me behavior. I have three (Sunpak 233, Minolta 360PX, Promaster 1700) battery-powered flashes which came with PC cords so you could use them on cameras which have a PC contact but not a hot shoe. However, only the Promaster will work with my Rolleicord III. Any flash gurus out there who know why this is? My *guess* is that there's been a small varitation in PC contact standards over the years, and my Rolleicord III uses a different standard.

 

[Uncle Goose]

mhhh, a flash contact is nothing more than a closing circuit, so it should have to work on all three. Is there by any change something on the Pc Cords that prevents correct attachment?? like too loose, or not inserted deep enough. Must be with the cord or PC socket.

 

[glbeas]

Try bending the center pin of the pc plug off center a bit on the ones that dont work, it may fix the problem.

 

[Vonder]

Same cord

Try bending the center pin of the pc plug off center a bit on the ones that dont work, it may fix the problem.

Same cord is used on all three flashes. Same cord works fine, fires all three flashes, when connected to the PC contact on a Canon EOS 3 body.

 

[glbeas]

Yes thats odd. Would there happen to be a hot shoe on those flashes as well? It may be the contacts are being shorted somehow if they are mounted on a plain slide in mount without contacts. A slip of tape in the right spot will determine that.

 

[John Koehrer]

I'm a little surprised that the same PC cord works on all three flash units.
You're problem may be poor contact at the flash, not the camera. It could be length or slight difference in diameter.

 

[Steve Smith]

Or it could be carbonised contacts in the camera itself providing an increased resistance path.

One flash is o.k. but the contacts cannot pass enough current to fire the other two.

If all three flashes fire when you short out the contacts on the lead, then the camera is the likely cause.

Steve.

 

[Ole]

If the promaster has a higher trigger voltage than the others, that could explain why only that one fires - if the contact in the camera is sligyly oxidised. Check the warnings about high trigger voltage and d*g*tal cameras - I bet the Promaster is on the list of "do not use"!

 

[Vonder]

I never listen to those warnings

If the promaster has a higher trigger voltage than the others, that could explain why only that one fires - if the contact in the camera is sligyly oxidised. Check the warnings about high trigger voltage and d*g*tal cameras - I bet the Promaster is on the list of "do not use"!

I've never had a problem with any flash. Maybe I will, down the road, but haven't paid it much mind. I base that on my basic electronics knowledge gained from being an electronics tech in the US Navy. We were taught that current and voltage are the two sides of the same coin, with power being the ultimate, end equation. So a 5 volt circuit at 1 amp of current is a 5 watt system, just as a 10 volt system at .5 amps is. True, certain electronic parts require either current or voltage to reach a certain level, but the damage (all electical systems damage their conductor, slightly) is the same for equivalent wattage systems. So the "safe" flashes might be safe voltage-wise, but are of higher current than the "unsafe" ones.

Now, admitedly, I'm not an electronics expert and my logic may be way off here. Engineer-types feel free to rebutt me, but do it gently with lots of lube.

 

[Mike Kovacs]

See what happens when you put 300 volts onto the wrong contact of a hot shoe, e.g. one designed for 5 volt ICs.

I think you are wrong about the flashes - yes in terms of the stored power that gets sent through the flash tube whether the flash is modern or not. But on a flash that power separated from the trigger with a relay. All you need is enough power to close the relay.

 

[Vonder]

I don't agree. Can you tell me why?

See what happens when you put 300 volts onto the wrong contact of a hot shoe, e.g. one designed for 5 volt ICs.

I think you are wrong about the flashes - yes in terms of the stored power that gets sent through the flash tube whether the flash is modern or not. But on a flash that power separated from the trigger with a relay. All you need is enough power to close the relay.

I would counter-argue that you can put 300 volts at 0.1 amps into any circuit designed for 6 volts at 5 amp and although I may not get the desired reaction, I won't harm the circuit. If you put 300 volts through at 5 amps, yes, you'll blow it to kingdom come.

 

[glbeas]

I would counter-argue that you can put 300 volts at 0.1 amps into any circuit designed for 6 volts at 5 amp and although I may not get the desired reaction, I won't harm the circuit. If you put 300 volts through at 5 amps, yes, you'll blow it to kingdom come.

That may be for mechanical contacts but the some of the newer cameras, especially the digital use transistors or integrated circuits to fire the flash and semiconductors definitely see voltage and amperage differently.