Flashgun gone mad

I have a Humax TTL flash, which worked fine on my K7, but when I put it on the K5, in TTL mode, it goes mad and keeps flashing, often before I have fired the shutter. It then keeps flashing like a crazy set of disco lights until I turn it off. Sometimes it seems to work normally (ie as a PTTL flash on its normal setting) when set to first curtain synch. It does not work in manual at all. It could be the flash, or perhaps operator error (I don't use the flash much; perhaps I am setting the cmaera up wrongly?), or is there perhaps something different about the K5? Any advice appreciated, we are having a party tonight and I would like to use the flash without inducing any epileptic fits!

I've read about this issue before so it seems to be a known issue with the K5 (and maybe K-r) and some third party flashes.

If you search the web, you will find a couple of threads about this issue.

Thanks, I have done a bit of research, and it seems unfixable, as Pentax have changed the resistance on the centre pin. It seems a lot of different makes of flashes have this problem on the K5.

Hey ho, yet another K5 glitch to add to the ever-expanding list!

I understand your annoyance and frustration. However without proof that the K5 no longer adheres to the PTTL specification, you can not say that it's a K5 glitch.

Humax might have reverse engineered PTTL instead of designing a flash based on the (paper) specification; I don't know. But reverse engineering can cause this type of problems (timing, signal levels, ...).

Although not every hardware issue can be solved with software, there might be a firmware update for the Humax that solves the issue (I don't know if Humax has (the option of) firmware updates).

PS I'm interested in a link to the info about the resistance. So if possible ...