Arcam FMJ D33 motorboating

I have an Arcam DAC with various inputs
Any input (USB, coax, optical)once selected will switch over and motor boat with no output.
Checked power supplies, onboard fuse, etc.
It uses dual PCM1792 dacs so its not isolated to one channel.
Thinking this is a digital issue somewhere between the CMOS ASCI chip, Gate chip and DAC since the XMOS is working as well.
It uses a CMOS ASIC (UART) capable of receiving and transmitting up to 16 channels of audio data in accordance with the IEEE 1394standard. Thinking the chip is toast