I have a 1620 bulk and I “updated” it to 1620 pro following Kenny Shin instructions, now my current firmware is B7T9.
Everything went ok and my drive worked fine for a few weeks, burning more than 30 dvds and cds.
But the drive stopped working 2 days ago: it doesn’t even burns cds at low speed 
.
I’m considering replacing it since it’s still in warranty, but i fear the warranty won’t cover the drive with this firmware.
Is it possible to flash to the original G firmware??
thanks.