Try hooking up a VGA monitor and seeing if you get any display, I don't have a GCT handy to tell you the header label but as I recall it's the 10 pin header near the CPU... it's a 2mm header like the IDE interface below is the pinouts (same as the i-Opener) the CN1 connecter is the labeled header on the i-opener, I don't recall what it is on the GCT.
If you get nothing from that, if the IDE header has been soldered on, check for short circuits esp if the solder job is messy. I have brought a couple dead gct's back from the grave by applying a hot soldering iron to confirm connections on the header.
CN1 VGA Signal
1 1 RED
3 2 GREEN
5 3 BLUE
X 4 reserved (Don't Connect)
8,10 5 GROUND
8,10 6 RED GROUND
8,10 7 GREEN GROUND
8,10 8 BLUE GROUND
6 9 +5 VDC
8,10 10 SIGNAL GROUND
X 11 montior ID Bit 0 (Don't Connect)
2 12 DDC Serial Data Line (UnTested ?/ Don't Connect)
7 13 Horizontal Sync
9 14 Vertical Sync
4 15 DDC Data Clock Line (UnTested ?/ Don't Connect)
