Don't bother poking around the power supply, the problem is definitely on the A main board. Take a close look into all the HDMI connectors and see if there isn't a displaced pin on even one of the inputs. One displaced pin shoved up against another can wreak havoc with the whole group of inputs.
I can't get a schematic up because Panasonic's service website has been down for some time, but older A boards used a separate HDMI select chip, which as you would imagine, would do the selection of the wanted HDMI input and funnel it out to the main IC. These are pretty tightly packed surface mount chips, but are replaceable. We see them fail most often in the summer, when lightning activity whacks these chips. It's possible yours was damaged through one port, and the chip has been limping along and finally failed.
Later Panasonics incorporated the HDMI select into the main chip directly. Since these are ball grid ICs, you're better off replacing the A board.
Before doing anything, you could try reflashing the firmware, although I've never seen this solve the problem on a Panasonic as it has for other brands.
On Sunday, February 23, 2014 1:52:33 PM UTC-5, Samuel M. Goldwasser wrote:
Hi:
I have this set, about 3-1/3 years old, used lightly.
About a year ago, HDMI 2 stopped working. Yesterday, HDMI 1 and 3 died.
A Panasonic Blu-ray player connected to any of these returns U72 or U73 - "The
HDMI connection acts unusually. The connected equipment is not HDMI
compatible.".
This had been working fine. The only thing that works through HDMI now is
that the player turns on the TV and switches to the connected HDMI input,
which is blank. After a few seconds the player displays U72 or U73 but it
continues playing.
Composite, Component, and the Tuner still work.
Google returns a variety of problems with A/V inputs on Panasonic TVs
but besides replacing the "A" board ($$$ and who knows if any given version
will be compatible) or resetting to factory defaults, I haven't seen a
solution. I have umplugged the TV for a few minutes with no change.
I'm reluctant to do the Factory Reset but will try that if necessary and
there's a chance it will work.
Thanks!
--
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