Troubleshooting a Quatitray sealer

I need help on this machine;the heater rotates with the roller that seals the plastic tray when passed through it.

The problem is that it has voltage on the slip rings where it is fed from PCB where the heater receives its power. When the heater is connected, the voltage just disappeared.

Something to do with the circuit that drives the controllers but I just don't know where to start my trouble shooting

Any tip is highly appreciated,.

Thanks

TM