450D won't fire flash on ttl cable

NeilG40

NeilG40

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Further to my post in the jessop 300afd thread it seems my limited knowledge of diodes caught me out and it was fine all along.

Anyway the flash will fire when it's mounted on the camera but not when it's on the end of the ttl cable. I've tried shorting out the pins on the cable and the flash fires so the cable seems fine.

Am I missing something?

Thanks
 
checked its properly secured down (done that before after spending ages fiddling to find the flash has slipped off the trigger)?
 
Yes everything is secure. I thinking about removing the diode tonight when I get home from work, I'm wondering if it's cutting the voltage too much for the flash to register. I'm not such what purpose it has anyway.
 
So as long as I don't use any other flash I'll be fine and by the time I get a flash that has manual control I'll probably buy some radio triggers too.
 
Well it's still not working . I'm completely baffled and a bit annoyed as I was hoping to use it next week whilst I'm on holiday.
 
I've had the multimeter out again, with the cable attached to the camera I get a reading which drops to 4ohms at the flash end of the cable when I press the shutter button. Surely that's not enough resistance to stop the flash firing?
 
can't be too much resistance, they're logic level voltages like 6V

are there any other canon users in barnsley so you can try another body/flash/cable to test?

makes no sense, your certain about the connections at each end and that theres nothing on the pad like a plastic cover (done that before with cables)
 
I imagine there will be other canon users but personally I don't know anyone with more than a compact.
 
sounds like a faulty cable since the flash and camera work together. you definetly got the right cable so the pins are in the right place?
 
Well it says oc-e3 on it which is the same number as the canon version, all the pins seem to line up and when I've got it connected I can get into the external flash menu on the camera.
 
try changing a flash custom function with the cable and see if its been changed by then putting the flash on camera and checking ;)

if ti has then the 4 comms pins have to be working, either there's something wrong with the quench pin or you have flash firing disabled in the menu

if you have a multimeter try checking conductivity on the big pin in the middle ;)

also maybe try the flash on manual though this is unlikely to help
 
I just changed the flash to second curtain and the exposure compensation with the flash on the cable, then I removed it put it straight on the camera looked at the menu again and the settings were the same.

If you mean checking the big pin from one end of the cable to the other the resistance is 1.2ohms.

Its just a cheap jessops flash so doesn't have manual only ttl.
 
animal168 said:
I dont know if it its of any interest to you but my jessops flash and jessops cable only worked together on my 450d when i set the camera to 200 synch speed. i bought a proper canon cable and it works perfectly now with the jessops flash.
Click to expand...

I tried it but it made no difference.
 
right so thats a perfectly rational impedance, there's nowt wrong with the quench pin which means it should fire regardless of the other four pins......

where the male end of the cable has spring loaded pins does the quench pin stick out as far as the others, they all stick out the same distance on my 430

also check both ends of the cable for dirt as this one has me stumped
 
david1701 said:
right so thats a perfectly rational impedance, there's nowt wrong with the quench pin which means it should fire regardless of the other four pins......

where the male end of the cable has spring loaded pins does the quench pin stick out as far as the others, they all stick out the same distance on my 430
Click to expand...

yeah there all the same height

david1701 said:
also check both ends of the cable for dirt as this one has me stumped
Click to expand...

It's completely baffled me too, I get paid on Monday so I'm thinking of giving it up as a bad job and ordering some skyports.
 
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