Water under unit

I'm sorry to hear this.

If you're really lucky, and it was just wet while you were first testing it, it will have dried off since then and might work now. However, the odds are better that the problem is not a wet board, but rather a corroded board.

The water must have caused corrosion on the traces and/or components in the audio portion of the circuit board.

First unplugg the unit and all the cables. Use a good light to help you look inside the center of the audio jacks. Can you see any corrosion inside the jack? If yes, roll up a piece of emery cloth small enough to put inside and use it to clean the jack.

If that doesn't work, the unit would have to be taken apart. All the connectors removed. You MAY have to remove the VCR assembly if it is sitting over top of the circuit board. That's not fun.

The object is to remove the entire circuit board so you can put it on a bench or table. You'll need a good light and a magnifying glass.
You have to examine the entire circuit board for patches of rust. Pay particular attention to the bottom of the board as it was closest to the water.

Check the components for corroded leads,
check the ports where they are mounted to the board,
check the wiring harness connectors,
check the general condition of the board and the traces. Any traces that have rusted through will have to be repaired using jumper wire and solder. Rusted components will have to be reattached using solder, or replaced if they are unrepairable. Contaminated harness connectors will have to be resoldered at least, and may need jumper wire to repair traces they connect to. They may also require their pins to be cleaned, and the corrosponding harness may also need its matching connector cleaned. Check the harnesses for broken or rusted through wires and repair accordingly.

That's a lot of work, but it's unlikely you'll need to do all of it.
Once you find the rust, you can concentrate on that area and do a general check of the board after the repair.

If this isn't your cup of tea, time to buy a new one.