I have a Denon avr 391 and it worked fine for 4 years. Now I cannot get any sound out of it. Any idea what's going on. Help

are there more than one hdmi connectors on the amp? Have you tried another?

Do a code search method. If there is a code, you can set it. If you wish to get more details, check this site. Pull up older posts there. http://electronicshelponline.blogspot.com/ Setup code list and setup proceedings to many popular brand remote controls are given. Two digit, three digit, four digit and five digit setup code list to different models remote controls are given. If you search the site in Timeslide option, which can be selected from the drop down list at the top left of the display window, it will be easy to locate the related post. You can also do a search by type in the brand name and model number to your device into its search box at the top right of display window. Check this site too. http://electrohelponline.blogspot.com/

I'm afraid that sounds like an issue with the power supply that feeds the main power amps. Especially on all channels. Could be the capacitors associated with the power supply. Sometimes you can see them bulging or even stuff coming out of them!

It's hot. Manual, page 65

http://www.retrevo.com/support/Denon-AVR-1908-Receivers-manual/id/5885ci670/t/2/

Sure it does:

http://www.retrevo.com/support/Denon-AVR-391-Receivers-manual/id/23705bh449/t/2/

Analog RCA cables go to anything available: DVD; SAT/CBL; DOCK
and/or
Digital audio goes to whatever is available: COAXIAL (SAT/CBL) or OPTICAL(TV)

Seems you cannot fix this issue yourself. If the unit is still under warranty, Denon will replace a chip which has a flawed firmware. The unit cannot be updated remotely and a physical repair is necessary.

try plugging another device into the tv input and mank sure you have the input mode is set to auto if you still have no sound those inputs are gone
http://www.usa.denon.com/ArchivedAVReceivers.asp?archivedModelSearch=true&clearCurrent=true&archivedCategory=AV&archivedModel=AVR-587&imageField.x=106&imageField.y=8

Help with hooking PS3 to a Denon Receiver. It worked before, but I had to move everything to a different location and when I hooked it back up the PS3 has sound but no picture. I have it hooked directly to the receiver with and HDMI cable (the receiver is hooked up to our cable box which is directly hooked to the tv via HDMI cable).

REPLACE MUTING TRANSISTORS IN DSP PANEL

If DIGITAL sign on the display blink, it mean the DSP board is defective. probably the DSP itself