If the battery is known to be fully charged, or at least near it, then it could well point to the main input fuse having blown for some reason, although its known that these fuses can sometimes go for no apparent reason. By the way the fuses are special soldered in miniature types only really obtainable from JVC, but there are other types on the market which can work OK if carefully soldered in over the top of the faulty one. Needless to say the side casing has to be removed to gain access to the aforementioned fuse.