Sounds like you need to get your power from another source. It sounds like (to me, no electrical expert) that you are wired into the small voltage regulator for the dash lights.
Maybe you should try to wire it to the hot side of the ingition switch. This should give you enough power to run the radio with no problems with the lights.....just a thought....good luck.
Maybe you should try to wire it to the hot side of the ingition switch. This should give you enough power to run the radio with no problems with the lights.....just a thought....good luck.