I have personally had experience with this issue. Double check that you can write to the DemoN NAND fine and not just the retail side. Beeping but no power is almost always soldering. I checked mine and it looked good but I had the same problem as you. At the same time though the tip I had been using was started to get a bit dirty and not hold solder so well right in the middle I was installing a DemoN in my own personal Xbox. So I went out and got some tip cleaner, cleaned the my irons tip to a shine and then redid all of the QSB points so that they were nice and shiny balls and BAM it works beautifully now. Also while doing my first DemoN a while ago around when it came out I was using a larger tip size (now I bought some nice and tiny ones just for DemoN installs ) and while double I found that two of the QSB points looked like they had connected but when I looked very close they were just connected to the QSB point on the DemoN and not the actual point on the board.I tried flashing a new NAND yesterday through J-Runner. I forgot to unplug the power cord for 30 seconds and now it just beeps but won't turn on. The retail side works fine, and I can still read the NAND through j-runner. How can I fix this?