The most obvious method is to simply look for bulged or leaking caps -- possibly even caps that simply look odd.
Then replace them.
It's really not any different than the methodology used to repair JVC DVD recorders.
And we've archived quite a bit of info on that topic here: http://www.digitalfaq.com/forum/home...g-jvc-dvd.html
So open it up, and see what you can see.