DS Lite issue after replacing top screen

The top screen on my son's DS cracked. I replaced the screen and all went ok. When I try to power it on with no cartridge or a DS cartridge the green light turns on, the bottom screen flashes white and then the unit powers off. I tried putting a Gameboy game in and that works no problem. Even the sound it working from both speakers so it's clear that the soldering is ok and that the ribbon cable is connected ok. I also tried powering up with the screen completely disconnected. Again white flash and power-off and the Gameboy game works minus the sound. It's no longer under warranty (besides I probably voided it by trying to fix it myself.) Does anyone have an idea of what I can try next?