I bought a used pair of DSP5200 (Speakerlink) a few weeks ago. When I tested them at the seller, everything worked. But when I had connected them at home, after a while there was a beeping sound from one of the speakers (Master). I also felt on the back that it was getting very hot. I turned it off and waited a while until it had cooled down, but when I turned it on, there was the same beeping sound. When I put music on, the sound disappeared, but when I stopped the music, the beeping sound came back.
The back was still very hot. So I haven't done anything more with them to avoid damaging the elements.

Where should I start troubleshooting?

TV room: 861v8, UHD722,Front 2xDSP7200SE, DSP7200HCSE, Side DSP5200, Rear DSP33, DSW, Velodyne DD 15 Sub,
Roon Rock NUC, QNAP NAS, Chromecast Ultra, Apple TV, Cambridge Audio 752BD, Pro-ject Pre box S2 digital, Philips Pronto remotes, Supra LoRad Power.
Office: 800v3, MS200, DSP3100
Basement: MS600, 502, 557, Dynaudio 52se, Dynaudio Sub 250