Schematic for Sony STR-D311 needed
 

I just fixed a friend's Sony receiver. Nothing special. Put in new Sankens on one channel. Sounds good, and has been running on the test bench speakers for about 5 hours.

Thing is, when I push the B speaker switch to on (nothing connected) sound stops on the A speakers. Seems strange. Just wanted to check the schematic to see if it is supposed to do this for some reason if there is nothing hooked up to B. The B switch is a different type than the A switch for some reason. Just seems strange and wanted to be sure all is well before giving it back.

Nothing bad seems to be happening when B is on (outputs don;t heat up or anything) and music comes back as soon as it is switched back off.

Hmmm...

This is a low end receiver, and as such, the two speaker sets are wired in series (not parallel) when you activate both. So when you push the B button without any speakers connected to A, the circuit is open and voila, no sound. I've attached a clipping from the schematic of another low end Sony receiver (STR-DE405). You can see how the speakers are connected by examing it.

Thans I thought it might be something like that, then I thought, naw, it couldn't be THAT cheap. ;)

Yup, it is. Just fixed a Pioneer that does the same thing.

-Chris

At least it's not mine :)

Oh yeah! Ditto.