Yamaha DTXpress/DTXplorer/DTXtreme

Hi all

My Kick pad has just developed an intermittant fault.  It's now 
missing many beats (or they come out really quiet) and it's getting 
worse - it was all working fine.

I have a DTXpress 1 kit - I wonder if I have damaged it by playing 
it too hard.

I have tried some obvious things like chaging the jack lead.

The problem is still there even if I only play the Kick Pad so I 
know it's not a cross talk or similar problem - anyway it was 
working fine.

I was wondering if I should take it a part and have a look but I do 
not want to kill it completely.

Can anyone please help or point me in the right direction if this 
has been raised before.

Are there any diagrams available if I do decide to take it apart?

If it is broken can it be fixed or replaced?

Many thanks