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Linked Canon 600's Won't Fire


Hoping to get some insight on something that is driving me crazy. I'm attempting to troubleshoot an issue I'm having with my three Canon 600 EX-RTs and my Canon ST-E3-RT transmitter.


Specifically, I'm trying to figure out what could cause linked flashes to (sometimes) not fire. For example, I usually set up my three Canon 600's to fire as radio slaves in Group Mode since I like to be able to adjust the settings of each flash individually. Sometimes my set up works, and other times, it won't. I ensure that all are on the same channel, same ID, the correct settings, that all are charged and ready to fire...I will use the test/pilot on my transmitter and everything will fire, but then when I go to click the shutter - no flash.


Before a wedding I'll test my 600's using my wireless transmitter and they'll work perfectly. I get to the wedding reception and they will not fire - using literally, exactly the same settings. I've had to resort to using one of my flashes on-camera as the master to fire the other two, and that always works, without fail.


I cannot figure out the cause or even potential cause of the issue...any thoughts? Many thanks for any help.



The only two things I can think of is (besides the obvious doubt about something wrong with your ST-E3-RT controller):


1. The slaves turned themselves off to save power and might have trouble waking up.  You might want to set the option to disable auto power off on the flashes.


2. There might be some electromagnetic power interferences that may prevent proper operation.  There might be a possibility some guests at the wedding are using the same Channel and ID as you.  I'd suggest you change your channel to something different from default as well as the ID.  The channel change will also change the transmission frequency and that may help. In my case I use channel 3 with ID 1234 instead of the default 1 & 0000.

Diverhank's photos on Flickr

Thank you so much for your ideas! I did ensure that all units were still powered up (I disabled the auto power off) and linked/ready to fire. I use a different ID and toggled through different channels to see if there was interference on my current channel, which was Ch 6.


I would have thought #2 was a strong contender for the root of the issue, but again last night I was testing out new equipment and my flashes initially did not fire. After attempting to change settings and giving up and going back to my original settings, the flashes began to fire.


Because everything works flawlessly when I use one of the flashes as the master, I'm wondering if it is an issue with my transmitter.


Thanks again, diverhank!

I've thought of a few more things...


1. the ST-E3-RT does have a sleep mode also.

2. You can do a channel scan on the ST-E3-RT to determine the best channel to use prior to a shoot.

3. How far were the slaves?  There's a limit to the range.  Also, I didn't remember this until I reread the manual...even though it's radio, it helps to point the front of the slaves bodies towards the transmitter.

Diverhank's photos on Flickr

Oh thank you - I appreciate your thoughts so much.


1. Pretty sure it wasn't #1, as I was actively using the transmitter at the time

2. I've not tried this! I will do that for sure.

3. Last night, slaves were fewer than 4ft away - all three of them. And all slaves were facing away from me, pointed towards my subject. However at the reception I mentioned initially, the fronts of all slaves were pointed in my direction.


I'll try a combination of all of these things the next time my flashes won't fire. Thank you again - I truly appreciate your correspondence!