pioneer sc-05 - all sound coming through center channell

We've got a fairly new system, with a Pioneer SC-05 receiver. We had the local store that sold it to us (Magnolia) hook it up for us. Everything was working when the technician left, but at some point over the last several months things changed so that now all the sound is coming from the front center channel. This is for all audio: movies, other audio sources, etc. I've tried cycling through all the settings in "standard surround" and "advanced surround", to no avail. (There are 5 speakers in the ceiling, and a separate subwoofer.)

I can't seem to find anyplace on the receiver to manually change things like front rear (or even right/left) balance, so I don't have any way to confirm that things still fundamentally work. I've confirmed that everything is still plugged in in the back, and of course no one's touched the wires running through the ceiling.

Any ideas on how to troubleshoot this?

thanks!!

I can't seem to find anyplace on the receiver to manually change things like front rear (or even right/left) balance, so I don't have any way to confirm that things still fundamentally work.

This generation of AVRs does not have manual controls for those functions. You need to go into the setup menu and change the levels there. One quick test is to run the "test tone" test. The AVR generates a white noise used to calibrate each channel. With the help of a spl meter (sound pressure level meter), the volume of each channel/speaker can be set individually in the menu. This test will let you know which channels/speakers are working and which are not.

hope this helps
dave