I had a similar problem with a Goodmans GDB2. The box 
appeared dead, with no TV display. The standby light was 
a dim red, the function light was a brighter red which 
flashed with the remote control was pressed. I referred 
to 
http://gdb.helpbytes.co.uk/
to attempt to update the firmware via RS232 port, but 
didn't get any messages from Hyper Terminal on reset.
After unplugging the unit from the mains I opened the box 
(four screws on the bottom, two on the back, carefully 
slide the top back and don't catch any wires inside). I 
carefully examined the two circuit boards and saw that 
one electrolytic capacitor C713 on the power supply board 
had a slightly bowed top where the inscribed X was. The 
lid was slightly brown above this spot and the capacitor 
was navy blue rather than dark royal blue. This indicated 
to me that the capacitor had failed by overheating, 
changing the outer colour and boiling inside which 
buckled the can. (There are also a couple of naturally 
black capacitors so don't be fooled.)
This is a power supply board, half of which is working at 
230V AC, so if you don't know what you are doing or can't 
solder or use a multimeter then stop here and get someone 
who is competent to fix it.
I unplugged the mains cable and the two signal connectors 
(each has two clips which you can carefully lever out of 
the way with a screwdriver before unplugging the 
connector.) from the circuit board. I then unscrewed the 
circuit board (eight screws) and slid it to the front to 
disengage the SCART connector and reset button from the 
back panel.
I then unsoldered the failed capacitor, tested it with a 
multimeter, and replaced it with a new capacitor of the 
same rating. The failed capacitor was a 1000uF, 16V made 
by G-LUXON; GR 85degreesC 209B(M). I replaced it with a 
1000uF 16V capacitor from Maplin's, part number VH50E, 
price 50 pence.
http://www.maplin.co.uk/
I then replaced the circuit board, replaced the screws, 
replaced the connectors, replaced the lid and screws. I 
then turned it on without it being plugged into the TV, 
then pressed the on/off red button on the remote control 
and the standby light went green. I then saw that things 
looked good and plugged it into the TV and the box was 
working.
I then upgraded to the main_7day_epg_gdb2_20041125.bin 
firmware following the instructions on Helpbytes and 
everything now works.
                
 Andrew
                
 March 2007