I did not have to solder to get it to work either but the brightness is not ideal. In daylight the backlight is not able to "overpower" ambient lighting without the wire soldered. I haven't yet been able to solder the power wire but I hope it'll improve daylight playability (note: it's still way better than a non-lit GBA or a front lit GBA SP in regular daytime ambient lighting, but far from what the display looked in the AGS101 or clone consoles like the revo k101.