have you tried the simple things maybe you could re seat some of the
connectors and check solder connections. im not familiar with that model
so i dont know how old it is, if there are any pots make sure you clean
them, you can use wd40 but its slightly risky as few pots are made of
chemicals that break down in the presence of oil. depending on age , you
may have some bad caps, i usually look for any of the electrolytic type
that are bulging, or have already busted. above all - clean it well inside
an out, sometimes even dust can be conductive and will cause a lot of
problems