K5synth

Hello all, 
I was playing my K5 earlier today (through the headphones) when it
made a "crack/pop" sound.  The volume level then dropped, and now when
I play a loud Multi (such as loud horns or loud strings) the output
distorts.  Sigles now seem quiter.  In fact, it seems that all the
outputs (headphones, mix, 1-4) are all now a lot quiter.  Everything
else seems to work perfectly.

I think an op-amp or part of the amp circuit went out.  Any ideas out
there on what my problem is and how to fix it?  Does anyone know which
op-amp controls the headphones (IC1, 4, 8 and 9 or something else)? 
If one of these ICs went bad I guess I have to replace it - but I need
to isolate the problem and change only the bad parts. (It doesn't look
like it will be a lot of fun changing out one of these ICs.)


Also, I plan on doing the 147k resistor hack very soon.  Any chance
this will fix the problem?  

By any chance, does anyone have schematics for the k5 they could turn
in to a .pdf and post?  That would help me a lot in seeing what the
problem might be.

Thanks in advance for any advice.