Problem with my Sega CDX

[darkshadow1804]

hi there!
i recently got a Sega CDX from a guy, that told me the console runs just perfect, but not playing the sega cd games sometimes...so i remembered that that is caused by insufficient amps (he used a 1200mA 9v transformer instead of 1500mA or higher)...so i plugged my 2000mA 9v one into it, and tried with a genesis game first (SONIC 2, yay!)...the genesis part works flawlessly, while the LCD screen says GAME on it...but when i power it on without a cartridge, it's supposedly to run in sega CD mode, the CD inside spins a bit, but nothing happens, just a plain black screen (and hissing noises on the headphone jack), and the LCD displays GAME only, not ACCESS...so i thought that the cd drive could be faulty, but it isn't, because i put in a couple of AA batteries and tried the CD player mode, and works very well without having ANY difficulty to read an audio CD, so...
what the problem could be?

i post a video to show you the problem:



could be the 12Mhz CPU, the BIOS or a DRAM chip dead? or just as simple as a faulty resistor or capacitor?
help! i don't want to get it back to the guy that sold it to me without having a clue of what is wrong with it and being able to fix it

thanks in advance!!!