After scratching my head over the broken Marantz I finally determined a cause of death.
Some friendly folks at diyaudio.com brought to my attention that the failure I experienced could have been caused if the speaker outputs were crossed, thus overloading the Darrington transistors.
Thinking back to the day it happened I had pulled out the receiver earlier in the day to hook up a Sega Saturn (which only produces stereo sound. eg: no center channel used) after playing that for a while the system was shut off. We returned hours later intending to play Xbox 360 (which is setup for surround sound. eg: center channel is used) and when the system was switched to the surround input by the harmony remote moments after being powered on is when it sparked an popped.
The crossed speaker wire theory fits because a few stray strands could have easily been grounded to the chassis or the other side of the speaker output when I pulled it out for use with the Saturn and then that channel wasn’t used until hours later when it popped.
Also there is no indication of any other component in the unit failing. Having 6 identical amplification circuits I was able to test the dead circuit agains the working ones and aside from the part that blew everything checked out ok.
After researching parts I found that the transistor that blew is discontinued… replacing it would cost me $10 worth of parts + $8 shipping. that and I was a bit worried that maybe I was missing something and the next time I powered it up it would pop.
I decided to simply reconfigure the amp internally. Since it’s a 6.1 Receiver and I never use the Rear Center channel I basically just re-pinned the amp connector to use the rear center channel amp for the Front Center channel. then I removed a few other key component from the original Front Center Channel to ensure that it wouldn’t receiver power.
After putting it back together and testing it works great… just as it always has.
Since I’ve got a new receiver now I’ll be selling off the old one… I’ve got all of the original accessories, manual, even the original box it came in. I figure considering it’s age and what happened I’d probably let it go for $120 or so.
I’m also going to get rid of the two Component Video/Optical switches I’ve got as well as the HDMI switch I’ve got and I’m thinking about selling off my PS1 and Gamecube as well since I don’t use either anymore.