Had one of these come in for repair-- looked like it was already in another shop. The common problem: loss of function control, remote and on-set buttons. Stuck forever on one source, ect. I see the failure is commonly remedied by replacing the mainboard, but why are so many of these sets failing? Is it chip related, as in processor or memory, firmware corruption, SMPS related? I know the qualtiy of iLO/ Funai isn't stellar, but this failure is a bit too common for too many customers. I'm just wondering if anyone has a clue, closer to component level, of what fails in these sets.
A common fault is the main processor, or in the I/O circuits that work with the main communications buss. That is why the board is replaced. It would not be feasible to service at the component level.
I found this explanation from someone who appears to think they know why it fails:
"it is the brain/micro/audio/video processor board it is what makes things work in the set. I have replace the board 100x for this exact problem and every time it has fixed the issue. I doubt many people have explained why you have had the problem but it was no fault of yours or even of the LCD itself, it was a design flaw of the remote which was not a fine tuned frequency and confuses the microprocessor and makes it think it has been told to do something it shouldn't have protects itself. The remote was built with the frequencies not set properly at the factory and when it got bad data from the remote the micro blows on the sets main board. I have spent weeks trying to bypass the data line no go they connected both the buttons on the set (less the power button) and the remote buttons on the same data line. There is only one fix brain surgery replace the brain with a new brain and replace the remote so it does not dameg your new brain. The new board comes with new software and new coding on the remote,"
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A common fault is the main processor, or in the I/O circuits that work
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While that explanation is appealing, it fails the logic test. Consider how a remote works: You press a key, it sends a set of pulses to the TV. These pulses get passed on to a processer which translates them into the equivalent of button presses. There are no 'self destruct' commands possible.
The real reson is far more mundane. Take a look at the main board of a TV. I recently worked on the 'Small Signal Board' (AKA Main Board) for a plasma TV. This 8" x 12" board had three distinct processors on it, as well as several periperal chips which were as complex as many programmable processors. One of those processers, the 'standby' processor is responsible for interpreting the signal from the remote, and if the 'Power' button is pressed, turning on the main power supply and monitoring the start up processes of the rest of the TV. This requires a section of the board equivalent to an early PC to be functioning perfectly. Above all, if the flash memory is corrupted, if the standby power supply is not operating up to specs (The 5.2V standby supply is actually used to provide the 3.3, 2.5, and 1.25 volts required by the standby processor), nothing happens.
As far as repairing the board, first you have to be able to diagnose the problem. This board DID have JTAG connections, and presumably with appropriate software it would be possible to diagnose the problem. However, look at it from the service shop point of view. Are you going to tie up thousands of dollars in a JTAG system so an unusually skilled tech can identify the problem? Then tie up thousands more into a rework system so a skilled reworker can replace a 120 pin IC?
As far as the reason for the component's failure, a lot of blame has been placed on the emphasis on reducing the use of lead. At the macro level, lead-free solder just doesn't work as well as the old 63/37 eutectic we all relied on. The situation is even worse when you get inside the IC. The tin/lead mixture that was used for bonding in the past has ben replaced with pure tin. Unfortunately, pure tin has the tendency to produce whiskers over time. And with the extremely fine wires being used, and the very narrow spaces between pads, those whiskers tend to short to adjacent pads.
While I am all in favor of making the home safe for children, I can't help but think very few toddlers have ingested a measurable amount of lead by chewing open an IC and eating the internal connections.
I don't think doing away with the lead in modern electronics was based on toddlers eating ICs. I think it had more to do with the massive amounts of throw away electronics that make it into land fills and the like. And probably an equal amount of liberal bullshit. I imagine that soon you will have to call lead abatement to do a full house cleanup if vintage equipment is found on the premises.
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