I'm pretty sure about the signal not getting through the big damn chip. The question is whether it is a software or hardware problem. If you go to sho pjimmys and look at a picture of the main board fro that model, alot of tho se traes from the HDMI jacks go straight to a big BGA flat thing with a hea tsink. The page is here :
Next to each HDMI jack is a little SMD transistor, no doubt a buffer for wh atever data an HDMI device wants to tell the micro. Now if plugging in a mo dern device (which he has) causes the set to switch to that input (which it did) and it does not produce a picture, the test is inconclusive. the IC t hat selects the HDMI input could simply be bad, but on the other hand it ma y not have neen initialized properly. this can be caused by a bad micro, or more likely corrupt data. the corrupt data can be caused by a defective EP ROM.
Now actually, EPROMS don't go bad as often as the used to, and I think that shitty power supplies cause alot of data corruption. they depend on specif ic capacitances in electrolytics for an orderly power down sometimes, which ois shitty engineering because the never gain ESR and/or lose capacity at the same rate over time. In a three year old unit, the screwup could have h appened once when turned on cold in a certain mode, or whatever. It depends on too much to be analysable effectively withoput a hell of alot of inform ation and equipment we do not have.
If I could reverse engineer a data port on the thing and had a properly wor king unit, I would indeed try to load the data from the EPROM in the workiu ng unit into the non-working unit. I would say that most likely it would fi x it.
I would then consider modifying the power supply to make a recurrance less likely. Most likely I would be forced to trust the engineers to have design ed it so that a sustained Vcc or Vdd to the micro and EPROM would not damag e the ports by having the other supplies slam down on the protection diodes in all the other ICs.
Of course all this is not going to happen. I've never dealt with load EPROM S manually using a PC. I know RCA's Chipper Check software has suck a funct ion. I also know tha tin other electronic fields it is done sometimes, but they are working on expensive equipment that justifies the cost of all this horseshit. If we could get EPROM images when these sets are new, that owul d not be so bad, but where the hell are you going to find the exact same mo del, and I mean exact. Just because it has the same model number does not m ean it is the same model. I have found this out enough times...
So we are down to replacing the board, because if it is a software problem you can change ALL the parts and not fix it. Got one someone broke in half ? go ahead and just change the EPROM. It is SMD but it's only eight pins. I t is doable, even for us old guys who can't see.
But get one.