Panasonic SC-Pt660

I think your problem could be that this Panasonic does not support "up-conversion". I believe that the HDMI is only for the DVD player output. Please put a DVD in and see if it plays on your TV. If it does, but the cable box does not play thru the HDMI, it is most likely that it is not supported. I alsop beleive that you do not have any HDMI inputs on the Panasonic, just an HDMI output. That would also indicate that the DVD player only is used for HDMI output.

You would need to connect the main unit's component output to the TV as well as the HDMI and use the component input of your TV for the cable box. I do not have a users manual fo rthis model, but I checked the service manual and it only ahows that the DVD player has output to the HDMI. Don't ask me why they would do it this way, it makes no sense to me.But that is what I seen in the schematics.

You could also try using this reset method, it could clear any errors you have, but would return the unit to the factory settings. You would then need to input all of your custom settings.

RESET PROCEDURE:

In STOP (no disc)
mode, press [STOP]
button on the main unit,
and [ 10] button on the
remote control unit.

Cancelled automatically
5 seconds later.

Let me know if this helps, or what you come up with.
Thanks,

Dave