Low voltage on voltage inverter board. I have 12 volts going to the voltage inverter board coming

Question

I have 12 volts going to the voltage inverter board coming from the main board until I plug the connector into the inverter board. Then, it drops to about 5 volts. If I connect an external 12 volt 1 amp DC adapter to the 12 volt lead, the voltage comes up to almost 10 volts and I can see the picture good. There is no sign of any burned components and all other voltages look fine. Any help would be appreciated. Thank you very much Frank