Yamaha rv1105 turns on for 3 seconds and then shuts off ??any ideas

You will find it has a power amplifier issue. Take it to an authorised Yamaha repair centre.

MY guess would be one of 2 things.

1) Power adapter faulty
2) Socket where adapter plugs in has a bad solder joint.

Turn on the keyboard and push the plug on the back of the keyboard up ( hold in upright position ) if it doesn't shut down / or alternatively doesn't work investigate solder connections to pcb for the socket. They often fail and break the track on the pcb. Repair as needed

I had the XM antenna plug come loose. In the process of trying to re solder it I had to remove the small shield over the plug. With the shield removed the reciever would shut off after 3 seconds. Once I soldered the shield back on it stayed powered up. I hope this helps.

Sounds to me like you have either your speaker wires crossed, the pos and neg are touching, or a pos is touching the case of the receiver.

try removing all the speaker cables and power back on, a loopback causes this same effect.

ur speaker system is short,check it with multimeter and remove the fault

Hi...
All the speakers are connected at both ends?
If so, you have a power amp electrical break.
Not an easy fix.

Get another receiver! I had the same problem and had the power supply replaced $250 and after 3 months it started doing the same thing.  I just purchased a Pinoeer Elite VSX 90TXV.

yamaha receivers protect themselfs when the power transistors at the output section are shorted, I just posted what you can look for this failure.