Well, I'm sitting here listening to music playing from this "dead" RioCar now!

The unit arrived in the mail earlier today, and I have spent a few hours cutting and resoldering traces to isolate the fault.

The problem was a stuck "D5" line (data bit 5) on the peripheral (ISA) bus.

I traced this signal down to the IDE header, the USB chip, the CS4231A, and the Ethernet port. As well as to a 3V/5V line transceiver connecting to the processor/memory bus.

The line transceiver was first up, and checked out okay on both sides.

Next, the USB chip. Again okay. Damn.

Next, the CS4231A -- I lifted the D5 pin, and connected it directly to the line transceiver in an isolated fashion -- the chip passed self test first try. Good resoldering job there, whoever did the chip replacement!

Next, as everything so far was innocent, I lifted D5 from the ethernet chip. Bingo.. system boots with audio etc.. Reconnect the pin again, and all dies. So, I'm going to leave it at that.

Cheers