Vintage Synth Repair

Hi-

I own a Roland D-50 which has a problem which seems to be typical of 
these keyboards.  The velocity sensitivity is not working properly.  
In fact, there seems to be no velocity at all on any of the keys.  
I've heard about there being problems with a few keys having velocity 
problems, but not all the keys being out.  This is what I did so far:

I found out that my aftertouch is fine; I did an initialization test, 
and it was okay.  It looks like the only problem I have is with the 
velocity.  When I do the initialization test, it reads "127" on all 
keys--nothing in between, just on-off, 0-127.  

I've called Roland up and found out that the whole keyswitch assembly 
parts (the contact assembly under the keys)are still available, but 
when I asked them, "..but my aftertouch sensitivity is fine on all 
keys; would replacing the keyswitch parts fix the velocity problem," 
all I got for an answer was "well, that would be a good place to 
start, it's possible that could fix the problem."  in other words, 
VERY VAGUE ANSWERS.  The Customer Support desk did nothing but tell
me 
that I shouldn't be trying to fix the keyboard for fear of electric 
shock or damage to the keyboard.  

I have to say right now that I'm a PC tech; I pull out PC boards and 
all sorts of delicate, potentially dangerous stuff day in and day 
out--I've already had the D-50 apart to check out all the contacts.  
So Roland gave me the run-around on this issue, the keyboard is
pretty 
straightforward enough that I don't think I need a service center to 
do the work (which of course Roland suggests...ARRRGHH).  However, 
here's the question: the contact points work great for aftertouch,
why 
would they not work for velocity?  And all the keys work FINE for 
aftertouch, unless the contact boards under the keys have separate 
contacts for velocity AND aftertouch.

Next important question:  I was wondering what the PC board under the 
keyboard assembly is for.  It's about 4 or 5 inches square, and has 
cables going from it into the keyboard assembly.  Do any of you know 
what this PC board is for?  Does it control velocity and aftertouch, 
and function as some sort of "brain" for the keyboard controls?  I'm 
just wondering if someone spilled too much beer on the keyboard, 
shorted out some part of the board, and fried the velocity.  If the 
single PC board is the problem, then it will save me the excessive 
cost and aggravation of fixing the contacts (of course, that is if I 
can get the PC board from Roland).  Please let me know any details
you 
can about what I posted, and even some experiences any of you may
have 
had regarding this problem.  Thanks very much for any help on this 
matter.

-Santos Menendez