miniDSP 2x4 HD USB DAC+DSP repair.

[djsb]

This topic is to log my attempt to repair my miniDSP 2x4 HD USB DAC+DSP which has suddenly stopped outputting any sound. It has been turned on for a while, so maybe something in the power supply has developed a fault.

https://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4-hd?gad_source=1

I will first attach a few PCB photo's in order to aid orientation. There are no official schematics or other service information that I am aware of, so I have to try to fix this by doing some research and investigation on my own. I have made some initial checks on the op amp and linear regulator voltages, and they seem OK. I don't know where the negative supply for the audio op amps comes from. My next on the list for checking is the tps65261-1 switch mode regulator and all the yellow tantalum caps (close to the large aluminium SMD cap). There is Hiss from the amplifiers (I use 2 x stereo amps in an active filter setup) after a small delay startup, so the output stages (of which there are 4) appear to be OK. I will list the chips on this side of the PCB later.

[djsb]

Here is a photo of the reverse side of the PCB. I will list the chips on this side of the PCB later.