Alto Black 12 speaker ADAU1701, AK5388AEQ, AKM4396

Hi!

I am trying to repair an Alto Black 12 active speaker. This speaker is equipped with ADAU1701 DSP, AK5388AEQ ADC and an AKM4396 DAC. The problem is that a sizzling, beeping sound is heard on the input panel. The problem can be measured and heard after the DAC. There is no noise at the ADC input yet. The signal is clear. At first glance, I found a missing part on the panel. To be honest I don't know what role a UHS Inverter (NC7SZ04) has, but a capacitor is missing from the + and GND pins. Can the lack of this part cause hissing and humming?

Can you help me with what is causing this problem?
Images and a video of the problem: Google Drive link

Sorry for the bad english.

Thank you very much,
Gabor



C28 capacitor is missing.
[edited by: DarioRossi98 at 8:21 PM (GMT -4) on 23 Apr 2021]