Cassette Player Lights staying on

I have a 93 GMC ( same as a Chevy, basically, right? ) that has had, I just found out, a working tape player all along. Seems the old owner unplugged the thing cause the lights stay on even when the truck is shut off. Anyone have any exerience with this? It has the separate player right in the dash right front of the middle passenger, complete with equalizer. Thanks in advance. ( I hate to take it to a Stereo store, because we don't have one way out here in the boonies )