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Resistors get out of tolerance and affect the Ohms which makes it impossible to handshake, and will cause things to appear dead.
Heat can burn anything out, even a diode. Burned up means anything that got too hot affecting its tolerance, it doesn't refer to something that literally melted to the board (though that can definitely happen, some types of resistors can even explode, but it is more common with capacitors to bust).
When things heat up too much, it changes the properties of the metal part which affects the resistance (among other things). Sure they make them heat resistant, but sometimes not heat resistant enough. The point is the component is no longer doing its job. Even the board itself and the electrical paths can be warped with enough heat over time. As far as being a complete short circuit, that is also possible but not very common. It certainly does not take a full short circuit to affect the HDMI signal, not even close. The digital encoding relies on the wave variance of the signal, and if this gets too far out of spec at any point, it will fail to be decoded.
There are literally thousands of posts in the receiver forums about failed HDMI ports, the HDMI boards fail because the MFR crammed too many parts too close together. The second most common reason is a faulty cheapo component on the HDMI board. As far as HDMI failing simply because of hooking and unhooking up live signals, this has been tested many many times by reviewers, and you can read about it online. It takes quite the jolt to fry an HDMI port this way. This about as common of a problem as USB ports failing from hot plugging, sure it happens, but it's certainly not common.
I'm not questioning your ability to repair an HDMI board, my point is sometimes the board doesn't even need replaced.
OF course anyone can replace the entire board, that's obvious, but that's too expensive, it's not even worth it.
Last edited by coderguy; 10-14-2019 at 06:19 AM.