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600exrt and trigger constantly lose connection.


I think it is ashamed that Canon can not create a fix for the constantly dropping slaves (600exrt) They are virtually useless off camera. Four or  five shots then got to stop and reset. Had to buy Godox at 1/3 the price to get a working speed lite radio group! Come on Canon!


Product Expert
Product Expert

Greetings gviper,

Let's check a few things to see if we're able to resolve the wireless flash issue you're experiencing.

  1. Ensure that there is one unit configured as the sender, and the other units are configured to as receivers.
  2. Check that all the units are configured to use the same channel and confirm same wireless radio ID between the sender and the receiver units.
  3. Check that the sender unit on the hotshoe has a solid and consistent connection. Check that local, non-wireless flash use works properly with a unit on the camera’s hotshoe. Also, you can check to see if the sender and receiver can successfully test fire when the sender is not on the camera’s hotshoe but will later drop the connection.
  4. Attempt to use different channels. This is an attempt to eliminate RF interference in the local environment. Please note that different channels could be required in different shooting locations.
  5. If the above steps are correct and there are still issues and then check to see if you can use optical transmission instead of radio transmission to trigger the off-camera flash units.

If you're still experiencing issues once the above steps have been completed, then we ask for you to send your equipment to our facility for service.

  • Label the equipment like if you're using two flash units where one is the sender and the other is the receiver. This can be done with anything from post-it notes to pieces of painter’s tape but please use something that can be removed without marring the surface of the equipment. Each unit should be sent in as it was configured (do not change any settings or reset the equipment), and labeled with:
    • If the unit is configured as the sender or receiver.
    • The channel the unit is configured to.
    • If applicable, the group the unit is assigned to.
    • Please do not reset/alter the equipment’s settings.
  • Write up a description of the issue you are experiencing, including if you are using radio or optical triggering, the camera body being used (if not being included), distance between sender and receiver, and if possible, a description of the environment (are there radio or cell towers nearby, is the location residential or commercial, etc.).
  • Send the equipment to the Costa Mesa facility:
    Canon Factory Service Center
    123 Paularino Ave
    Costa Mesa, CA 92626-3311
  • Include all the flash equipment used.

Canon U.S.A., Inc. has created a new online repair portal that allows you to set up service in a few simple steps. The repair portal gives you the ability to set up service for multiple pieces of equipment at once, and to receive a repair estimate in the majority of cases, depending on your model and issue. The portal also allows you to upload images or videos that will assist us in repairing your product. You can also select how you wish to be notified of the progress of your repair. The portal's service history section allows you to view all services that have been performed on any of your camera or video products since January 7, 2020.

Please follow the link below to access our online repair portal to arrange for service:

Instructions for Accessing and Using the Online Repair Portal.

You will need to access or create your My Canon Account.

If you already have a My Canon Account and your product is already registered, simply click on the “Get Repair Services” link on the left menu and follow the onscreen instructions to arrange for service for your product.

If you have a My Canon Account and your product is not registered, you must register your product first. Click on the “Get Repair Services” link on the left menu, then click on the “Register Product” link on the right. After your product is registered, click on the “Get Repair Service” link on the left menu and follow the onscreen instructions to arrange for service for your product.

If you do not have a My Canon Account, you will need to create one. After you create your account, click on the “Add Product” link to register your first product. After your product is registered, click on the “Get Repair Service” link on the left menu and follow the onscreen instructions to arrange for service for your product.

Once you have completed the repair request, you will have an opportunity to print a copy of the request for your records. This request form will also contain shipping instructions and an address label that you will attach to the outside of your shipping box when mailing your equipment for repair.

I cured it. I went to GODEX. they work perfectly.


I appreciate the information. However the situations Canon is asking for is only one particular moment in time. Not real life working environment. We have been using the once reliable system without issue regarding Link Drop” now for over Ten years since first purchased in 2012 in all types of different scenarios, E-TTL, Manual, All, Group Mode etc. at home with a Cell tower less then a Km from my house. Take them on the job to any particular different location inside or outside, never a problem.
For me it started January 2023. “Link Drop” 
Sent all 4 600 EX-RT’s and two ST-E3 RT’s to Canon Virginia, to have firmware updated as described in an official Canon site regarding issues with 7 or more malfunctioning. 
My units were to have new firmware updated, only the Transmitters were updated. Both now have a Silver Sharpie Dot on inside of Battery Cover. Also both the Transmitter have Sender, not Master. 
Regarding the 600 EX-RT’s, no dot, still read Master or Slave AND most importantly not upgraded to new firmware. Why not as they said they would? Complete the job! 
Still the same issue, “Link Drop”, no matter if E-TTl, Manual, Group Mode. One flash, all flashes, one Transmitter or the other. A 600 as Master and Others as Slaves. 
Changing to all 15 Channels one by one and changing an ID… no not all 10,000.

Canon Virginia only connected the System in the controlled environment at the repair facility for only a few seconds, not allowing to have a chance to see if Link Drop occurs after 5 minutes. 
And let’s stop with “Optical”… not a real life option as we use these once reliable system in soft boxes with line of sight disrupted. Optical was nice with a 7D pop up flash and a 580 EX-II prior to 2012. 
Until Canon identifies the issue, and has a permanent “ Fix” identified, there is no reason I will send my units into Canon Costa Mesa. 
Unfortunately the EL-1 is having the same issues. Maybe its the Radio Communication hardware?



Hi, Nick55. 

Please get in touch with support for any questions regarding repairs that were performed previously. The Product Experts cannot pull up your personal information via the Canon Community Forums. Support is available Monday through Friday from 9am to 9pm (ET) and Saturday from 9am to 8pm (ET). 

For anyone else experiencing this, please know that this directive is brand new, and our Factory Service Technicians are trying to understand why the flashes are suddenly encountering this phenomenon. They cannot perform valuable research without triaging your units in-house.

Maybe Canon needs to set up Mobile Army Surgical Hospitals in the Battlefields to perform Triage, not in a controlled environment


Canon fails to even acknowledge the issues, why should they care, they have the money already from the purchased hardware. Then you will find out  you need third party Godox to make it workable. 


I don’t have time to be sending my flashes back to Canon/CPS. Canon, do your own testing. Stop recommending optical triggering, it is not reliable what so ever. Optical works great in a bathroom stall, not a large event space. I didn’t spend $1000 on the EL-1’s for that, wtf.


It seems like this started recently for everyone, including myself. I used to have zero issues with the ST-E3-RT firing off my 600EXs, but as of about a year ago, this is not the case. They lose link every 2 min or so, no matter the channel. And it always happens to me in a building with a cell tower installed on the rooftop.