Yamaha DTXpress/DTXplorer/DTXtreme

Hi... 

Long time lurker here to the group. I have a DTXpress II kit and the
kick pad is giving me some trouble. I'm getting rapid fire triggers
from a single hit or sometimes I'm getting no trigger response at all. 

I'm sure it's the trigger in the pad unit. I've been beating the thing
without mercy with a Pearl Power-Shifter double bass pedal for 2-1/2
years now. The pad itself is worn thin and sunken in. 

Is this something I can replace myself or do I have to buy a whole new
kick pad tower assembly?? 

Can anybody recommend an online source for this stuff. I want to buy a
couple of cymbal pads also.

Thanx,
Dennis.....