This is a really strange fault that caused me a lot of grief.
The timing was unfortunate as it added to the confusion, but it turned out to be an uncanny coincidence.
My solar system went live on December 4. At the same time my AV room developed a hum/buzz on all channels. I searched high and low for a ground loop and never found one.
The strange thing was that the hum was on all channels, was unaffected by volume setting and did not go away activating the mute on the 7705. So I thought it may have been something to do with the solar panels. An Internet search confirmed that as a possibility. So I ordered a power cable for my AVP with and RF blocker, and it made no difference.
So then I got curious to find out if you could hear it on headphones. I could not. This is where the story gets strange. When I removed the headphones the hum was gone.
Despite this I was suspicious there was trouble afoot and there was. So I phoned Scott of Hi-Fi sound and talked to him. Like me he was of the opinion that problems would return. He gave me a deal on a Marantz 7706 I could not refuse. It was significantly below any Internet price. I picked it up just before Christmas, but was too busy to install it, as we had a lot going on. Well at the end of last week, I got at an enormous speaker busting thumb from all channels and the hum returned but with a vengeance. A soft reset made the hume quieter, and the headphone trick worked again. However on checking the system the output to the left surround back had totally failed. Luckily no speakers were damaged. But is I did not select very robust drivers, there probably would have been.
So yesterday my eldest son came over to help me install the 7706 in the rack.
So, I spent last night and a good deal of today making the connections and doing the set up. I carefully kept note of all the settings, as I wanted it to sound the same as before.
I am glad to report that, at this time the 7706 is working perfectly.
The question becomes of what to do with the 7705. It has been in use for 5 years and 3 months. It has had intensive use.
The options are to send it for recycling or have it repaired by an authorized service center and sell it on. This is by far the most serious problem I have encountered with any of the six AVPs I have owned. The first, a Rotel was sold on, because it had no HDMI. The others are still working. My Marantz 8003 has been boxed in storage for quite a few years. It was working fine when I took it out of service. That unit had a failed voltage regulator in less then a month of service and was quickly repaired under warranty and there were no subsequent issues.
AVPs and AVRs are the very heart of AV systems and just about the whole system communicates with them. Installation and set up is a huge task.
