12v DC power supply output rather high? Try this:

If your dc to dc psu gives higher than expected voltage output...say more than 360v dc. Then it could be that your power transistors really are turning too hard on. Increase the 470 ohm base resistors to 680 ohm. This should result in less power being drawn from the 12v supply and deliver 350v on receive and 305v on key down. These figures will allow the paraset to perform well and are provided for guidance. You might get something slightly different.