Check that you have good comms with a scope, make sure you have valid rs232 levels coming in and out of the board.

Check you are using a crystal that will give you the baud rate ! The best choice is an 11.059 Mhz one, which works from 110 to 19200 baud.

Check your ram and its addressing - a '52 BASIC needs a minimum of 1k to wake up - if it can't find it, it will sit resolutely silent, whilst it clocks its address space.

Check your reset lines are valid.

Doubt everything !

Also note that Jan Waclewek has very thoughtfully re-engineered 8052 basic into our modern 89C51 FLASH versions. Other have modded it into the Dallas 80C320 too.

Steve