Roland HP505 distorted sounds

[Nyqusit5]

So I got this piano's power and analog output board running thanks to the kind help of "doctor". But I am now facing the original reason for this piano to come in here: all of the tones are distorted on all outputs. Speaker, Line ou and headphone outputs are distorted.

The symetrical supply rails and 5V supply are good but it seems that the left and right signals coming out of the DSP board aren't clean. My guess is that an opamp driving the output is toasted but unfortunately, the schematic isn't available and the board is all smd.

Has anybody encoutered such a behaviour on this piano?

[doctor]

If the sound is distorted both at speakers and line outs, most likely you have a problem either before DAC or in DAC itself. Find what DAC is used, see its datasheets and check by scope at DAC outputs whether the signal is distorted (consider that you can only see the signal if the DAC is “voltage output” type). If you see distorted signal, replace the DAC. If this does not help, you need to replace main board complete.
If you see undistorted signal, the problem is in after-DAC operational amplifiers and you are lucky.

[Nyqusit5]

If the sound is distorted both at speakers and line outs, most likely you have a problem either before DAC or in DAC itself. Find what DAC is used, see its datasheets and check by scope at DAC outputs whether the signal is distorted (consider that you can only see the signal if the DAC is “voltage output” type). If you see distorted signal, replace the DAC. If this does not help, you need to replace main board complete.
If you see undistorted signal, the problem is in after-DAC operational amplifiers and you are lucky.

Thanks. Which one is the first op amp right after the DAC (if you have the schematic)?

[doctor]

I have not the scheme of the main board - Roland does not provide it.

[Jazz P Bass]

To add to the Doctor's post, it may help narrow down the issue by, yes, downloading the DAC datasheet.

With a scope, observe the signal going into the IC first.