Geeetech

I have recently picked up a faulty a10m with the hope of fixing it up. symptom is no power (but there is a red led lit on motherboard)
Apparently it has had one replacement motherboard already.
I have the old and new board, both of which are gt2560 v3 models - one has large eloctrolytic cap replacement.
Both have a blown 10A fuse. I have ordered some new fuses, but clearly something is blowing the 10A fuses.
With the 10A fuse blown, should the device still power up? I see a red light on the motherboard when power applied, but nothing else to indicate any signs of life. What does the 10A fuse rail power? The 15A fuses are intact - what do they power?
My fuses are a long way off from delivery but when they arrive I intend to swap the 10A out for new and put in motherboard without any cables to motors, extruders, bed etc, then introduce one cable at a time to see if I can identify any one single part that may be blowing the fuses.
Anyone else experience this and/or has any further ideas?
I think what would be good to know, is does the board (and lcd) power up if the 10A is blown or removed - if so, then I may have another faulty motherboard that i would also need to replace.
I should also mention that I have hooked up the USB to my PC, but no new device (COM port) found.

Regards
Jason

So I have used a car mini blade fuse and hacked it to fit and now my board powers up.
I slowly added cables back in and tested.
Main power in added, and could see 2 red leds and an orange light flicker.
I then added the flex cable from the LCD and got the bootup screen - Marlin 1.1.8

I added the large power cable at the left which i assume is heating for flat bed. not sure if i should see temp go up, but seems static at 21deg atmo.
I added the X motor (left/right nozzle)and it moves smoothly on testing
I added the Y motor (forward/back flat bed) and it moves.
I added the Z motor (up/down height) and it moves, but sounds terrible at first but seems ok now?.
I wonder if this is what has been causing the fuse to blow??
I added e0/e1 and no diff. I think these are the filament empty sensors.
I added 3dt (3 pin and 2 pin) - what are these?
Lastly i have added E0 and E1 large cables for extruders and a fan on the inside of the nozzle spins up.
The outside fan on the nozzle is not running tho - is that normal

Lastly added the cover fan of motherboard area but as connector was only 2 ping but motherboard connector was 3 pin, had to double check what was ground and live before adding in - i wonder if this is in the wrong location, ie pos 2 and 3, does it cause a problem?


No fuse popped yet
I have done the autohome from the control panel and it seems to have worked, but the nozzle is lower than the flatbed - is that typical for the home position?