Why does a stock 93 am/fm cassette make electronic beep noises?

I was planning to replace the stock unit in my 93 Caprice wagon but on a lark today I put a cassette in it and got it to play. The radio part doesn't play but makes static with a 3 beep 1 beep pattern before repeating. Not positive there isn't another 3 or 1 beep in the pattern but you get the idea. Sounds like when a computer tries to boot up and beeps at you. I thought the unit was dead but the cassette playing makes me wonder. Power antenna wires were disconnected under the hood and I reconnected to find the beeping still going and an antenna that never quit running without going up or down so I know the antenna needs to be replaced. I have never run into a radio making those kind of noises before, or having the cassette work but the am/fm not work. The display also doesn't ever light up. Anybody got any ideas on the cause of the beeps?!

aliens,...

My relatives deny any responsibility!!
I first thought it might be theft lock but reading up found that only the cd players had theft lock.

There were a lot of issues with those radios, but they are also pretty common in the salvage yards and on Craigslist/Ebay. If you want to keep it stock it should be quick and easy.

You might want to upgrade to a later 94-96-style Chevy CD player.   Nicer readout and more modern, and you can purchase them, and an adaptor if needed, on Ebay.

Already have an aftermarket radio I was going to put in but very curious about the beeping and first time seeing the receiver not work but the tape working, always been the other way around.