I have the N model for Nikon
I've found nothing on the camera that could do it, except maybe the connection in the shoe.
Oh, BebuLamar I finally remembered to physically short out the fire terminal (center one) to the frame and it fired normally, just one flash.
I have used the Godox TT685n for 3 1/2 years with no problems. I generally use the i-TTL mode. Prior to that I used the Nikon SB600 until I physically broke it.
a) When the flash on the camera's speed is set to 250 (Auto) the HSS indicator on the flash comes on, I've set it for 250 with no (Auto) and the indicator is gone . b) no pre-flash setting on the menus that I've found but I did try an outside shot and had the same 2 pre-flashes. c) have searched online and the manual for pre-flash with none found, and the D850 is a big guy with no scene modes. While my memory was never dependable in some areas, I believe the flash test button worked when the camera was on. And thanks for exploring options with me.
Thanks for the encouragement.
It looks like I've repeated information that was not in a new post, sorry folks, but the problem remains unsolved.
I've added more information and accidentally started a new post. I'm adding the new information to the old post.
The unfortunate has occurred the problem is back. Removing the flash and replacing it has recreated the original problem. I've now taken it off and, on several times, and use my trusty pencil eraser to clean the contacts.
When off the camera the flash fires normally with the test button and when on the camera the test button does not fire the flash and when the camera fires it there are the two pre flashes.
More information: When the flash is on the camera and the camera is turned OFF the test button fires it normally when I turn the camera on the test button no longer fires the flash and firing the camera creates the two pre flashes.
Again: AGGGGH
More information: When the flash is on the camera and the camera is turned OFF the test button fires it normally when I turn the camera on the test button no longer fires the flash and firing the camera creates the two pre flashes.
Again: AGGGGH
When off the camera the flash fires normally with the test button and when on the camera the test button does not fire the flash and when the camera fires it there are the two pre flashes.
The unfortunate has occurred the problem is back. Removing the flash and replacing it has recreated the original problem. I've now taken it off and on several times and use my trusty pencil eraser to clean the contacts.
The OP is tickled to bits.
Yes and no problems before. I had the Nikon SB600 and it was physically broken and I didn't want to spend the money for an new Nikon flash. I'd been using Godox in my studio (nearly defunct now) and had liked them so I replaced the 600 with the TT685 which has very similar specs to the Nikon and have loved it. I do think it is more me than my equipment.
I press the button and it DID NOT flash. Took the flash off and the button worked. Put the flash back on and everything was back to normal. Now I cannot remember if in all this, at least 2 week process if I had removed the flash before but all is well and it works as it should. Thank you all for following and suggesting. Maybe age is beginning it's effects I'm 78 and maybe suddenly stupid.
Yes, HSS is enabled, I just disabled it and the I still get the two pre-flashes. AGGGGH.