Vintage Synth Repair

Hi-

Here's a problem I'm going to have to troubleshoot, and I would like 
some pointers if possible.  I own a Roland D-5, and the control panel 
lights (the performance-multitimbral-rhythm-mode light, the a/b 
selector light, and the first preset light in particular)fade out and 
are inconsistently lit.  I usually have to tap the top of the synth 
to get them working again, so it looks like a loose connection, since 
these three lights fade out at the same time.  

Now here's the question: How do I access the back of the control 
panel to get to those wires?  This is something I need to do 
carefully, of course, but the flakiness of the LED's might be a start 
of something else about to loosen, so I want to check it out.  I like 
the synth, even though it is an oldie, it's a great MIDI board, and I 
want to keep it maintained.  The patch/edit display screen is fine, 
and all the LED's work, so it just seems like a loose wire. Any 
suggestions would be great, thank you very much.

-Santos