5920G ATI HD3470 VGA MXM

Hi again to here, i tried to see here if one has something like i have now, i have this 5920G laptop ( my son ) when it come to home have a working ATI HD3470 VGA MXM card plugged and all is working, now after my other Acer lappy get failled we tried to see if can be 5920G upgraded with an ATI HD 3650, fit as right no problems, push down power button and seems all is fine but now have a blank screen, this 3650 seem not to work, we gotten back the 3470 to fit and get back to work the lappy but not success, same blank screen, light power up, HDD, ODD, and if plug USB-FDD same but still not to work, how we can get it done back to work with the ATI HD3470 ?
Thanks in advance.
Kanchata