In Need Of Help!

[///M-TRD3]

I was in my '88 535is yesterday and I noticed that the radio suddenly wouldnt come on, and my on board computer light has gone very dim (noticeably) the anit-theft has stayed on the radio and you cant turn it on now. Any ideas what happened or how I can go about fixing it?
Thanks

[razor/m5]

I beleive you have to have the key on the "on" position for about 30 min , then enter the code for the radio, not 100% sure though