My friend had a huge old Marantz receiver that he bought while he was in the Air Force, just before he got out. I don't remember the model number, but it was either the top of the line, or the one under it.
Almost from day one, it had problems. It would hum on the back channels intermittantly. He took it to the local warranty place here, and they found "no problem". It hummed as soon as he turned it on when he got it home. Another try, and this time, they fixed it.
Then, it started doing some weird "feedback" thing where it would suddenly start rumbling at a low level, then it would get louder and louder, to the point it would shut down. It was kind of like the movie "Earthquake" with Sensurround, or whatever they called it. The rumble was coming out of both the sub and front/surround pre outs. The power amps were fine, my receiver had no problems running them.
The volume had no effect, and once it started it didn't stop. Went to the local place again, and they did something, and it didn't affect it at all. Went back a couple more times, no good. At this point, Marantz was contacted, and it was sent someplace to get looked at. It came back about a month later, scratched up (It looked brand new when he sent it!) and it still did it. Obviously, they did open it up, since the screws were marred up on several PC boards inside and on the screws outside too. He complained to Marantz, and they said to send it back.
So he did, and it came back with a new faceplate, but it still had the rumble.
He called them again, and some guy came out to look at it, he just shook his head and laughed, and said, "I've never heard anything like that before". He sent it back again, and after two months, it came back, and still rumbled. He called them one last time, and just told them he wanted a replacement, he had been more than patient, so he was shocked when they refused, saying "Well, the unit is 18 months old now, and well out of warranty, perhaps you can get the dealer to help you!"
He tried to reason with them, but they just told him to check with the dealer.
Well, the dealer WAS in Hawaii, and they had gone out of business anyway. He sent letters to Marantz, and got nothing but a form letter saying "Have a nice day!'
He came over that afternoon, and plopped it on my porch, and said, "It's yours! If you can fix it, great, if not, it's parts!" He replaced it with an Onkyo that was recently just retired and moved to his kid's bedroom, replaced with a new Onkyo. I messed with it for a long time, with no luck. I did manage to isolate it to one PC board. I tried to find a replacement, but it cost an amazing amount, so I passed. I even tried replacing almost every component I could on that board, and accomplished nothing. Of course, I couldn't replace the likely culprit, a couple of big IC's with about a hundred leads each.
I've been very leery of buying anything made by Marantz since this happened.
I got a whole lot of good parts out of it though!
The heat sinks were sold to a friend of mine who used them on a 2-Meter ham linear amp. The amp boards were sold to another friend, who replaced the smoked power amp section of his home built integrated amp with them. Worked great. The rest of it, less chassis and faceplate is in my closet in boxes.
