The issue is either the SC board, one of the S buffer boards, or possibly the P, SS, or D board. Connectors P2, SC2, SC20, or D20 might be loose. Unplug the set. Check and reseat the connectors first. Replug and power... still blinking?
Unplug the set.
Disconnect the SC board (two connections, SC2 and SC20)
Plug the set in and try it.
- Does the set turn on and stay on (No blinks and of course no screen)? If so, reconnect the SC board and alternately try disconnecting the SU and SD boards. The board that makes the set blink is bad. If the set blinks with both the SU and SD disconnected, the SC board is bad. If the SC board replacement doesn't fix the issue the D board is bad. (Way to go with vague troubleshooting, Panasonic!)
- If the set still shuts down with a 7 blink error with the SC disconnected, attach a voltmeter to connector P25 pin 1. try turning the set on. Does 15VDC appear here, even if briefly? If not, the P board is bad. If so, test connector P2 pin 1 in the same way. If Vsus (about 180VDC on Panasonics) appears after turning the set on and before the set shuts down, the SS board is bad. If no Vsus, the P board is bad.
So says Panasonic.
If you don't measure
any Vsus in the last step, you might want to disconnect the SS board to see if that changes your readings. Disconnecting power to the SS board may generate a fault by itself and shut the set down, I'm not sure - different models behave differently.