Been wanting to do this mod to my DX7 for a while now but just havent gotten around to it yet.
http://dimensionengineering.com/appn...ektrum_mod.htm
If your Google skills are up to it...do some more research on the subject. While the above link will describe how to change out the voltage regulator, it doesnt cover how to reprogram the low voltage warning.
When you go to a 3cell lipo...the voltage is about .6 volts higher when fully charged compared to the stock NiMh battery. I have read it before but dont remember where...that you can reprogram the DX7 to warn at the correct time of low voltage so you wont end up killing your lipo by relying on the current programming telling you that your battery needs charged.
If you dont reprogram this feature set...and rely on the factory configured setting...you will drain the lipo too low and risk possible damage to the battery or your DX7. If you do not reprogram this...you should keep a check on volts per cell and recharge when you get around 3.7 volts per cell or so.
goodluck
PS...after this mod, or when using a lipo even without the mod...keep in mind you wont be able to use the charge jack on the TX any longer. Remove the lipo and charge on appropriate lipo charger.