PSOne controllers not working on PS2 ><;Follow

Hey all,

My only PS2 controller just decided to die on me. I thought I was okay since I still have my PSOne (the slimmer re-release of the PS1) with 2 perfectly fine controllers. Unfortunately the PS2 simply refuses to acknowledge them when I plug them in. I have tried re-booting the PS2 a few times, blowing their socket pins (lol) and trying a few games but the PS2 just won't accept them.

I have heard many times that the compatibility from PSOne > PS2 is fine for controllers. The controllers are both dual shock analogue identical the the PS2 controllers except they are white.

Can anyone suggest a fix or am I screwed?