As far as Hu cards not working, I've seen a few DUO-Rs where the solder joints for the Card slot go bad on the board. So it might just need to have all the pins for the card slot re-soldered. The 2nd possibility could be a Dirty card slot (fix by putting rubbing alcohol on a hu cards pins) or that one or more of the pins of the slot are actually bent/damaged. Usually these pins can be bent back into position again.
Most likely there isn't anything super major broken with the console since CD games load up just fine.
While you have the console open, you should also put new solder on the Power, AV, and Controllers ports. The solder for the pins on those all fail inside R and RX consoles as well.
R and RX consoles do not suffer from bad caps. Only the Black DUO systems have the bad cap problem.
If at any point you decide that you don't want to mess with the repair yourself just let me know and I can help out.
Most likely there isn't anything super major broken with the console since CD games load up just fine.
While you have the console open, you should also put new solder on the Power, AV, and Controllers ports. The solder for the pins on those all fail inside R and RX consoles as well.
R and RX consoles do not suffer from bad caps. Only the Black DUO systems have the bad cap problem.
If at any point you decide that you don't want to mess with the repair yourself just let me know and I can help out.