I have an RCA Home Theatre System RT2380BK that will not turn on anymore.
When I plug it in, the red standby light comes on. When I press the power
button, I hear the relay click on and the standby light goes out, but it
never says "Wecome" which is what it is supposed to do next. If I
disconnect the power supply from the rest of the circuit, it does the same
thing, but if I disconnect one of the display/control panel cables from a
main board, the relay doesn't click and the standby light doesn't go out.
(There are only 2 cables going from the display/control panel; the other one
goes to the on/off switch). I even removed the fuse from the power supply
and it did the same thing, but the fuse is good. Any ideas?

First thing i would do is locate the memory backup battery ( if it has
one ) usually found on the front board ( sometimes elsewhere ) It
usually looks much like a big watch battery . With the unit unplugged
from the power Take something and short across the battery for a few
seconds ... other than that ??? audio amp shorted ???

I have found several newer Pioneer receivers needing this treatment .