Marantz AVR trouble: one channel not working right

[BrianZ]

My brother-in-law has a modern Marantz AVR (SR6008 I believe) and after some troubleshooting we discovered that one channel is super low volume (front-left). Not intermittent like a dodgy connection or anything -- it's consistently very low volume. Is there anything we can look at relatively easily and try to fix? I'm handy with a soldering iron and have a killer set of tools, but I've never opened up a piece of home audio equip. Or is it definitely a trip to unauthorized service shop?

In general, I have always been curious about how these modern AVR multi channel amps work. Are there 7 separate amp circuits in there, such that just one can go bad? Or is it something else?

Thanks.

 

[MakeMineVinyl]

I would not recommend tearing into your receiver, as unless you know what to look for and have a schematic diagram of the circuitry, and know how the circuit is supposed to operate, there is probably little you can do. Manufacturers discontinued giving out schematic diagrams long ago, probably to discourage customers digging around and potentially doing something which could get the manufacturer into a lawsuit.

Without that schematic, there is no real way to know what to look for and where to look for it. It helps to be an experienced technician, but even they would probably need a schematic for an unfamiliar piece of gear.

Also, its quite likely that all or most of the preamp processing is done in the digital domain, and there is really nothing you can do if there is a problem there beyond just replacing circuit boards outright. Even technicians these days don't usually replace the actual electronic components on circuit boards, and just replace the whole board.

Of course you could open it and get lucky, and if the receiver is a loss otherwise, you might try to take a look. I don't think its a great use of time though.