Wondermega victor RG-M1, not playing cd rom games, only Audio cd , Help

Hi guys , sorry for bad englishI live in brazil.
I am a technician in electronics and i need some help. I have wordemega many years .. I disassembled the console that is now on my table, the optical drive is new, I have adjustments the all pots .. operation with the audio disc is perfect, changing tracks without fail .. when I put the cdrom game not recognizing the disc,, spinning without stopping (in normal speed) . Something interesting happened, I put the disc audio for awhile and then put the console recognized the cdrom .appears on the menu (cdrom), I pressed play, the sega logo appeared and froze ...
To recognize the cd rom game I need to put first a cd audio. This is random, it is not every time have success .. when appear in the menu (cdrom) , freezes after the sega logo .. honestly do not know what else to do .. normal power, clean flat cable, I have conditions to swap chips if necessary .. thanks !

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