They All Fail IMO
I called Onkyo customer service last year and explained that I had several failed receivers and complaints all over the Internet about this problem. I asked the very nice woman to please send email up the chain of command notifying Onkyo that their poor HDMI reliability was seriously damaging the brand.
I asked them to consider revising the HDMI thermal management. Perhaps they finally got the message, perhaps not.
My recommendation is that only an experienced DIYer should attempt this repair at home.
The repair procedure for the HDMI includes traditional static precautions as well as shorting two leads on the HDMI with a jumper to protect the board from static damage when it is removed. Apparently (my guess) there is a pin somewhere on a chip that has no static protection clamps in the pad ring (where the wirebonds connect the package pin to the die) and that pin will blow out if mishandled. Most likely the static protection was omitted to reduce input or output capacitance...
...at least that was what my employer did on one in-house custom IC design.
The Onkyo HDMI boards are difficult to remove. Several screws come out and then the cables must be removed appropriately or they will break. The release tabs must be pushed on the ribbon cable or the socket will cut the leads off the cable, and the flex strip has to be pulled out carefully with tweezers.
The connector sockets between the HDMI and its perpendicular interconnecting board along the side of the receiver are very tight. They have to be nudged apart with a screwdriver then carefully disconnected from each other by wiggling and pulling very hard at an angle to avoid shredding components that interfere with pulling straight.
The point is, replacing these HDMI boards is not for the novice technician. However, for an experienced repair person the procedure is relatively straightforward.
I bought a TX-SR606, TX-SR607, 2x TX-NR609, TX-SR705, TX-SR706, TX-NR929 all used.
Apparently the reason they were for sale is they were already failing.
All of them have failed HDMI except the TX-NR929 that was 'refurbished', probably less than 3 years old (my main receiver), and the TX-SR705 that had no sound output or video at all (I returned it).
All the HDMI failures were in evidence when I bought the receivers, but usually intermittent, especially once they warm up. None of the ones I tried out before buying showed any obvious failure but several began failing within hours of installation and one that had non-obvious symptoms started failing hard but intermittently within a couple of months, indicating the failures were all intermittent at first, developing slowly, and almost certainly known to the prior owner even though no one informed me the receiver they were selling had known issues (yes I did ask).
Perhaps one or two sellers had no idea but I doubt it. The main failure mode is lack of onscreen menu and video upscaling. These sorts of failures are hard to miss, especially when the onscreen menu suddenly stops displaying.
Repairing the HDMI board is another matter than replacing it. Good soldering skills are required as well as a knowledge of troubleshooting and not all the failure modes are the same, although cooked capacitors is the predominant failure mode especially in the newer models. The TX-SR705(?) and other similar models in that generation have both audio and HDMI failure modes that require adding a retrofit daughter board to repair it and are not worth the bother.
I have repaired the TX-SR606 and everything but the upscaler and menu are working now (maybe I blew the susceptible pin by not shorting it because the technical repair bulletin said nothing about it, or maybe the instructions I found on the Internet omitted some capacitors on the power supply for the upscaler that also seems to handle the menu that can be displayed in SD). Of the rest, only the TX-NR929 has no apparent HDMI failure yet and it is not 3 years old yet.
In the process of looking for solutions I found that there are some Youtube videos demonstrating a DIY repair and some Ebay vendors selling HDMI repairs for specific models at $75 and up plus shipping (different vendors come and go).
I also noticed numerous receivers listed on Ebay and Craigslist and Fixya etc. of many additional models disclosing HDMI failure including one that was only a processor with no amp or tuner. From this fact I speculate that all Onkyo models are susceptible and will fail eventually with enough hours under power unless some actual modification is added to protect them from heat.
The failure is due to excessive heat on the HDMI PCB. The DSP and HDMI etc. chips on the board have no heat sinks so they are actually using the entire PCB itself as the heat sink, meaning the heat is dumped into all the cooler running components on the PCB. Most likely IMO, the processor and HDMI chips that Onkyo used is an older (cheaper) larger dimension transistor IC technology with more transistor capacitance and higher aggregate switching dissipation than the board can safely handle.
The capacitors are only rated at 85C for 1000 hours (~40 days) so of course they eventually dry out and the power supply gets dirty. Then the digital communication starts getting bit errors and HDMI crypto key check starts failing, freezing all protected content intermittently. Eventually it will not sink up even in standard definition unprotected content and video screens of digital white noise start showing up while it tries to re-synch to the bitstream, then the video eventually fails entirely, especially the on-screen menu and upscaler that seem more sensitive.
Even when the amp is idling and the output stage is cool, even when there is no signal connection at all, the HDMI is pouring heat out through the vents in the lid.
Updating the design with newer, lower dissipation ICs and intelligent power management should eventually fix the issue for Onkyo in the newer models. I doubt they have any incentive to use heat sinks on the board or higher temp rated capacitors due to cost. When millions of units are in production over a decade, pennies count against the profit margin.
You get what you pay for and Onkyo has the best function/price ratio of any brand I know but probably the worst reliability as a result. Sony is relatively inexpensive too, but appears to have power amplifier failures and I do not like their feature set so I never bought one.
These descriptions of HDMI failure are all independent research and subjective observations on my part but I feel confident in my analysis.
I am still in the process of repairing the rest of the intermittently failing receivers. I expect my TX-NR929 will start failing within the next two years at which point I will have to repair that one too.
Only the Onkyo design team will know which of their products have been updated with lower dissipation chips and power management. If they keep putting more DSP into the board they might never fix the problem because they might just keep adding complexity and eating up the margin they gain back from other improvements. Only time will tell.
For now my recommendation is anyone who expects to keep their next receiver for more than 3 years should buy a Denon or Marantz or other model besides Onkyo that includes the best implementation of Audyssey room correction that one can afford. I am not impressed with the features and/or cost of other non-Onkyo brands (although I have little experience with them) but I do feel that Audyssey calibration is essential and unparalleled.
I also recommend that anyone with good electronics skills who has a need of many receivers at absolute bargain basement cost should buy used Onkyo (print this comment and use it to negotiate aggressively on price) and repair the HDMI as a DIY using the official Onkyo HDMI repair bulletin for the TX-SR606 as a rough guide (it has been leaked to the Internet) except ignore the directions to add a small ceramic bypass capacitor in parallel with the electrolytic because the problem is not effective series resistance but actual electrolytic capacitor failure.
I caught on to the HDMI failure after my second (no-test) used purchase of the TX-SR606 and chose to repair that one myself rather than return it because new prices and used competitor prices were just way too high for my plans. I used capacitors from my junk box that were probably 50 years old plus higher (12V) voltage rating and they have worked fine for over a year now but they are physically huge compared to the original surface mount. They needed to be laid sideways against the board and they needed longish wires to connect them but they still worked fine so I know the problem is not related to effective series resistance in any way, at least on on the five capacitors I replaced (the Onkyo bulletin only mentioned 4 but the Youtube video showed 5).
The solution is to replace (at least) all the power supply filter electrolytic capacitors possible (especially the surface mount 100uF 4V power supply filter capacitors) with leaded, high temp (105C for 1000 hours at least) capacitors. Use leaded capacitors and cut the leads long, bending the capacitor over if necessary for physical clearance, to keep the heat conductance to a minimum. Surface mount are in close contact with the PCB. Leaded capacitors can be positioned so that they are far enough away to avoid getting too much heat conducted into them. Convection and radiation will still warm them up but at least they will not be piping as much heat straight into the package through the leads.
If buying new, there is the possibility of mounting fans to the underside of the top lid so they can blow directly down onto the HDMI board whether the internal fans are present and running or not. That should work to prolong the life of the HDMI. Another solution is to glue heatsinks onto the hotter chips (be careful when feeling them because some get really hot and can burn you). Either modification will void the warranty so there is risk either way. Maybe wait until the warranty expires but then you risk protecting a board that is already on the verge of failure. Both these modifications are illustrated in posts here at AVS forum. Just search Onkyo HDMI.
I do not recommend buying the extended warranty on any electronic product as a general rule because on average the cost of the warranty on an expensive product just covers the cost of repairs but you pay in advance. Onkyo does repair many of these units, even some older models, but the repairs take a long time and requires moving the receiver. Instead of warranty I recommend putting the extra money into a reliable competitor's product and tossing it or dumping it on Craig's List when it eventually fails.
For the average person I definitely advocate doing your research first and then buying the best product you can manage rather than just going by maximum features for the lowest price, unless you are one who is constantly chasing the bleeding edge and will trade up in 3 years or less. No one wants to mess with failed equipment unless, as I mentioned, it can be had very cheaply and repaired very easily by a customer who already possesses the skills.
Please keep in mind that some Onkyo models such as the TX-SR606 usually had the HDMI failure within one year and the warranty replacement board also usually failed within one year. The failure rate of any model depends largely on whether the unit is installed in a cabinet with poor ventilation, whether other equipment or books and newspapers get stacked on top of it, whether it is placed on carpet and the bottom vents blocked/insulated by the pile of the carpet etc. so the more you do to keep the unit cool the longer it will last.
I do not have any direct knowledge of the reliability of the latest HDMI boards from Onkyo. We will have to wait and see. I do not trust any statements from the manufacturer.
That is the best I can do with this issue. Good luck.