Hi all..

I have a question about probabilities in troubleshooting a surface mount
mainboard in a Korg SP250 Digital Keyboard.

The mainboard uses a SAM9753 ('dream') DSP/controller, with digital
audio & clock signals going straight into a PCM1716E DAC, the stereo
output of which goes thru left/right low pass filters built on a
NJM4580M dual op-amp.

All power supply rails look good.

The mainboard passes its internal memory checks and MIDI loopback
checks, etc., which leads me to think the SAM9753 itself is ok.

I have seen reports of two other Kong instruments with similar
condition.. main DSP / power ok but no audio out.

I intend to report back here if I get to the bottom of it, but I was
wondering given the above what people would be inclined to suspect /
most likely failure of the following... solder, caps, the DAC chip, the
OpAmp, partial failure of the DSP chip? Unit is about 5-7 years old.