Hi Adam, thanks for your comprehensive reply. I should mention that I've troubleshot this pretty extensively already, and I'm hopeful that someone else has had this problem and can clue me in on the failure mode. The mute was checked and double checked, as was the input source. In fact, I've attempted to generate output using a variety of input/output combinations (including testing with/without headphones), hoping that there might be a port/connector failure somewhere or that the issue might be limited in scope. It doesn't appear that any input or output works, with the exception of HDMI pass through (but that doesn't really count). I've tried them all pre- and post- reset. Re: the tuner - while I didn't use it in the past, I was able to lock onto a signal using the FM antenna, and still got no output. Not even a hiss or static.
If HDMI pass through works, then the HDMI board is active. It has to work for pass through. If no inputs work and the radio does not work, it is a total waste of time and money to replace the HDMI board. I can be certain if that is the case it is not the HDMI board.
Do you use the headphone output a lot? If so, the problem might be the headphone muting circuit. Since there is no sound and yet the receiver does not go into shut down, it might be that the regulator controlling power to amp board in the power supply has failed, so that there is no power to the power amp board. Both of these issues would be pretty easy cheap fixes. I just have a hunch there is not much wrong with this unit.
The problem is it is a low cost unit, and it will take two to three hours to identify and fix the problem most likely. With the cost of running a repair shop, they really do need to get $100 an hour for labor plus parts. Repair techs have a really hard time making a living. That is why there are so few of them now.
For people in this hobby, it is well worth considering doing some night or community college classes to learn the art of electronic service. Good test equipment can be had on eBay for not much money.
You have to understand that Marantz do not make the components. However there are grades of components, from low tolerance all the way to aircraft and medical grade. As you go up the food chain the risk of failure goes down, but is never zero.
In addition to this being a low priced unit, it is a refurb. A lot of refurbs are basically open box. However, if a unit has had a failure, especially one involving shutdowns from the protection, then that unit has been stressed and will be more prone to failure form multiple causes. I do not recommend refurbs, for something as complex and trouble prone as receivers.
That brings me to the final point to avoid the lower price offerings from all manufacturers. If you don't want a repeat, start looking at the $600 and above, and look at Yamaha in that price range, as they are sparse on features. Preferably look at the $1000 to $1200 price bracket. The cheap receivers are prone to blow any time after two years and often sooner.
The bottom line is that the more expensive units are likely to be the better bargain.
