MCX8000 Input 4 without signal on phono and disturbed on line

Hi @here I have a problem with my MCX8000. The 4th input (Line 4/Phono) has an issue. When I just plug in a Turntable (and of course switch the little knob) I have zero signal. When I plug in another Signal (Line, CDJ or similar) I have only a smashed sound. Only one channel (red or white chinch) single plugged in works without disturbing the sound. Anybody any idea if I have to replace the entire soundboard or is there any other way to fix this? I know it is hard to say without the possibility to take a deeper look at the device itself, but maybe somebody already had a similar problem and fixed it…???

Plug in of standard RCA from Technics SL 1210 MK2 and knob to Phono is without any signal: When I plug in another line signal (CDJ or similar and knob to “line”) I only have a clean signal when only one RCA channel is connected. As soon as both are plugged in, it is distorted…

Ground is properly connected and cable is without any damage… It is working fine and clear when connected to Input 3/Phono

Cheerz and thanks ind advanced

As you mention, it’s difficult to diagnose this remotely.

I’ve known something similar to happen before where a line level cd deck was plugged into a mixer when it was playing , but the input was set to phono instead of line. Boom!

Also I know of a time someone tried to plug an electric guitar into line level rca connectors with similar results.

Both needed factory attention and board swaps.