Originally posted by mrdfred Are you saying that it is not a problem with with my camera, but a issue with the K-5? If so, getting another K-5 wouldn't solve the problem.
Indeed, another K5 will not solve it as far as I know. But I don't say that it's necessarily an issue in the K5. I don't know much about the technical side of PTTL (read: signal levels, currents, rise and fall times, timing, protocol). But there are two parties involved (flash and camera) and if one of them does not exactly adhere to the specification, it's calling for trouble somewhere along the line.
If Vivitar reverse engineered PTTL instead of designing a flash based on the (paper) specification then that is more than likely the cause of the problem. I don't know if they did but reverse engineering can cause this type of problems.
Any chance that you can update the firmware of the Vivitar and that there is a firmware update that solves the issue?
Recent thread on pentxuser.co.uk about problem with a Humax flash with similar symptoms:
Flashgun gone mad