I realize this is an old post, but if you are looking for a solution you might try this.
It has yet to fail for the 3 yellow blinks.
If you are seeing the 3 yellow blinks repeated over and over the
boot data is corrupted. Download the firmware update(link below)from
Toshiba and
unzip the files and folders,copy the unzipped files & folders to a
SD card (like a
camera uses,I used a 2 gig). Make sure it is a SD card because an SDHC will not work. Unplug the tv and insert the card into the slot hidden behind the cover above the HDMI inputs.
Plug in the tv and watch the yellow blinking stop and a solid blue will light when done. Unplug the tv, remove the card,plug in the tv and all will be good. You could now install the update per it's instructions if you wish. Enjoy !!!
www.tacp.toshiba.com/customersupport/model_firmware.asp?model=65hm167