"How can I fix my Panasonic SA-PT850? I can't open it. The display shows F61-7"
A quick Google search suggests this:
Error code ' F61 ' on most Panasonic models indicate that the built-in diagnostics has sensed a fault at the output stage. This would normally refer to a failed output amplifier IC. In some instances, the fault could also be triggered by:
* strands of Speaker wires inadvertently touching each other
* faulty speakers
* failed, clogged or blocked Cooling Fan of the output IC
Hope that helps
Anon, July 2016