Storage [Q] USB keyboard autosuspend(?) troubles

Is anyone using a USB keyboard with their Tab 3? I have wierd problems with mine on a 4.2.2 t315. If there is a pause of more than about 2s between key presses the next key press causes the screen to turn off, the next one turns it back on (locked), the third one unlockes it and the fourth one gets correctly registered. I suspect there is either a problem with my keyboard (don't currently have another to check) or with the USB autosuspend that is set to 2s. Unfortunately I have not yet rooted my Tab (a bit scared to lose the warranty) otherwise I woul check if I can owrride the default USB autosuspend.
Any experience with this kind of problem?