I have an older 21-speed Miyata MTB and had a problem with the paddle shifter for the front derailleur not functioning. I took apart the dual shifter mechanism to fix the problem. I found and fixed the problem, but unfortunately the assembly came apart. Now I cannot figure out how to get if back together. Does anyone knopw where to get older schematics for shifter assemblies? The shifter that I have is a Shimano Exage 500LX for the three front gears.