Yamaha CS80

hello Everyone.
I am Kenji from Japan, I am not really sure if
I can put my message on it since this is your
CS-80 place.  But I really want to know what I can
do on my GX-1. It seems to have some compativility
between GX-1 and CS-80, it is the reason
to encourage me to try to give
this message here  to ask some help.

I had chance to get this GX-1 last year after 4 years
effort.
The last owner said that he did not turn on last 20 yeas, so 
he was not sur which functions no longer worked.
When the first day I turned on, this guy worked quite well,
but everytime I played, something became bad and 
now there are so many things did not work. 
I wonder if any of you can advice me, or help me
to find the way to fix any of following;

1.solo key _sub ocilator speed
           _1st touch response
           _end touch response
           _volume rever(does not rink to main control)

      solo key has other problems
           _another phenomenan that U/L reverb rever linked to 
            control of solo volume

2.upper key_key assigner
           _touch response
           _portamento

I really love this instrument and 
want to keep as long as I can.
If key asigner can come back, I will be very happy
even if the others will not be fixed.

I would appreacite any of your advide.

if I bother you, I am very sorry.

Sincerely

Kenji from JAPAN.