I have a Hitachi P50H401 and had bad buffer boards. I replaced them with a good set (tested per the instructions I found here) from a P50S601. The boards look identical to the old ones and plug in all connections properly. The Y main was shot (per a reputable tech I've used in the past and is very knowledgeable), so I bought a refurbished unit off an Ebay dealer I've used before. When I power the TV on now, I get normal red standby led, but when I turn it "on", I get the blue light flashing 4 times repeatedly. The unit will not power down back into standby unless I unplug it. I've seen a lot of people here who've had the 3 blinks problem but not 4. Does anyone know if the P50S601 SDR chips will work in the P50H401 or could that be the root of my problem? I've tried unplugging the upper with lower attached and vise versa to no avail. Unit still wont fire up and blinks 4times. Any help or insight is greatly and sincerely appreciated.