A77 with yongnuo rf-602. Is 1/250 sync possible?

Hello guys. It's my first time posting here but have been a longtime lurker. I figure someone here can help me with this.

I have searched and searched with no definitive answer. I have the sony A77 (ver 1.06) and just received a set of the yongnuo rf-602 triggers. I cannot get sync above 1/160 without black band. 1/200 is very slight and 1/250 it almost fills half the frame.
I'm at a loss. I have also turned off SSS and electronic front curtain and nothing changes. Also put in fresh batteries. 
I did a couple of shots hardwired with a PC sync cable and it synced just fine. no black banding so it is definitely the triggers 
I have a generic hot shoe adapter? maybe this is the week link? I ordered another which will get here on friday.

In the case that it's not possible to get 1/250 sync with the rf-602 can someone recommend triggers that are reasonable priced that can. Maybe the cactus v5?

Anyone have a definitive answer.
Oh the flash is Yongnuo YN560 ii

Many thanks in advance

Cheers

TVH