Kenwood TM733a - Display stays dim
 

I acquired a TM733a which seems to work fine however the display
remains dim no matter what setting is used to chjange it - is it most
likely something as simple as a burned out display bulb, or possibly
something related to the CPU? The control for brightness is able to
turn the display OFF but cycling though the different values D1, D2,
etc make no noticeable change in the brightness. Thanks.