help on FD 2GS

[TRUC PHAN <TTPHAN@postoffice.worldnet.att.net>]

My Boy's Apple 2GS FD internal Controller broken down! First, it is not 
read 3.5 FD Disk! I think maybe the External FD bad so I bought another 
for him, The new one won't work neither. I can reject the Disk but the 
computer can't see this FD.( I did go to Control Panel and turn on Smart 
Drive Port AND the Disk Port)but system still can't see this 3.5 FD.
I also have dual 5-1/4 FD with external Card (from my old Apple2E) plug in 
slot 6 and HardDrive card plug in slot 7, It works good.
Anyone know how to check the internal FD controller og Apple 2GS ? If it 
is bad, could I buy another card to plug in? How much it cost? Or I buy 
the whole mother board? ( I think it cost $120 for mother board).
Please help! I am lost in this Old apple 2 world???