ctl-dcm laser Help.

Hi all, can some one point me in the right direction. I have picked up a second hand ctl-dcm 4 head lazer and the blue beam is no good (very dim) in fact you can't see it. I been all over the net and this seems to be common with the blue. I was wondering if I could just swop the blue laser with let's say a red or green or even more power full blue one. I have taken it apart and cleaned all the mirrors but no difference. I can see the laser I want to change and how it removes. But I don't know what I can safely fit with least amount of fuss. Every thing els is working fine.
Thanks