If you are experiencing an issue where you can't get you transmitter switched on, no power coming through so not lighting up, then if you have a Heng long black 27mhz transmitter it could be that the spacer tabs in the battery channels in the rear of the handset are getting in the way and holding the batteries too far apart. All you need to do to fix this is get some sharp side cutters remove these tabs, the batteries will the connect better and the handset should work as it should.