Paul C. Buff, Inc. Technical Forum

I have been using Einstein and CyberSync system for studio and location lighting for more than 2 years. On my camera bracket I use modified Nikon SC28 TTL cord with a hot shoe extension custom connected on flash end of this cord for CST, radio transmitters or 2nd fill flash. Paramount Cords make these custom cords. Following is link for this modified cord:
http://www.paramountcords.com/proddetail.asp?prod=HSFM-SC28S
To assemble gear for a shoot I connect camera on bracket, slide camera end of SC28 cord on camera's hot shoe, slide flash on flash end of SC28 cord and slide CST transmitter on custom hot shoe extension. With this setup I have used Nikon cameras D200, D300 and now D700, Nikon SB800 and SB900 flashes and PocketWizard Multimax, now replaced by cost effective CyberSync CST without any problems.
This year in February I upgraded flashes from Nikon SB800/SB900 to Nikon's latest flash SB910 and my above system quit working. I connected all pieces including new Nikon SB910 flash and CST as mentioned above, SB910 flash fired first time but stopped working and switched back to default settings on 2nd and onward clicks without effecting CST trigger and sync with camera. To locate problem I bought 2nd SB910 and found same result. Assembled equipment on my old bracket with Nikon SC29 modified TTL cord, same problem. Removed CST from hot shoe extension and connected with PC sync socket on SB910 flash using cord came with CST, same problem. Mounted Flash on camera and connected CST with PC sync socket on SB910 flash, same problem. Found an old flash and connected with SB910 PC sync socket using a matching cord, same problem. Connected a borrowed PocketWizard instead of CST, PROBLEM RESOLVED, worked as intended. Connected CST with Nikon D700 Body using CST cord, NO PROBLEM, worked as expected.
Conclusion is Nikon must have made some change in trigger circuit in SB910 flash which works with PocketWizard but does not work with CST and older flashes when connected in parallel to SB910 or using it's PC sync socket. Nikon completely ignored my emails. PCB tech support was of no help, Nikon was blamed for making an incompatible product. Right now I am using CST connected with Nikon D700 camera body's built in PC sync socket but it is an hassle, would like to go back to sliding CST on hot shoe extension. I would like to know and discuss if there are other Nikon/CyberSync users facing similar situation? I do have 3 CSTs and results are similar with all of them.

Did the probelem result in the SB910 locking up with no response after the first flash, while the CST operated normally (sorry, there is a lot of information in the above post, just trying to clarify)?

If so, this is a symptom I have seen with the SB800, and I believe the 900 series flashes as well. Usually, this revolves around the battery voltage of the CST. Even if the battery is sufficient to operate the CST without the low battery indicator (three blinks from the LED when fired), it can still cause a lock up condition in the flash unit if the voltage drops below a certain threshold (2.85VDC sounds familiar, but I am not sure at this point).

Usually, swapping to a fresh(er) battery resolved the issue. Unfortunately, the we have only been able to test on a single SB800, so I cannot for certain say if you are experiencing the same problem, or if the suggested solution will work.

There was also a change in how the communications work with the 900 or 910. This may or may not play a part in your issue as well.

Did the problem result in the SB910 locking up with no response after the first flash, while the CST operated normally (sorry, there is a lot of information in the above post, just trying to clarify)?
Yes, SB910 locks up after first fire while CST operates normally. Sorry for long details but I put all test results to speed up responses instead of receiving questions whether I tried this or that.
I have 3 CST's to test and NEVER had any problem with SB800 or SB900. Battery voltage was the answer given to me by PCB tech support. I do not wait for CST to wink at me, I use a battery tester and replace CST batteries at half way of their life, can not afford equipment failing in middle of an event. I have tested with fresh batteries in CST with same result.
I assume that only improvement between SB900 and SB910 is thermal cutoff, recycle and LCD, everything else same. For some unknown reason I never had any problem with SB900 or SB800 and CST as I am facing with SB910.
I will request PCB Tech support to repeat the test with a temporarily borrowed SB910 to locate or understand the problem.
There has to be some modification in SB910 sync circuit which is compatible with PocketWizard but not with CST. As mentioned in my previous post, right now I am using CST by connecting it with PC Sync socket on D700 but I would like to get back to my original rigged bracket by sliding it in hot shoe extension, makes it faster to assemble equipment on location.

Unfortunately, the likelyhood of us being able to perform this test is low, due to the lack of resources (both time available from our engineers as well as accessibility to an SB910). Even if we were, it does not sound like we would find much more than a compatible/not compatible result, if we found a definitive result at all.