Picked up one of these up yesterday ($12.95) It seemes to work fine on
both AM and FM. Through some internet research someone suggested
replacing the (rectifier?) selenium diode because they can explode and
catch fire. Someone also stated that later models do not have the
selenium diode. How do I identify this thing and what should I replace
it with?

Also, how's this set for sound and sensitivity. It seems to sound
great for a table top. Is that a pizo tweeter in there? Also can the
AM loop antenna be replaced with a ferrite coil for better DX?

Thanks