Why does my iPhone 4 only power on when connected to power
I recently bought an iPhone 4 as spares/repairs with a error 21 upon restore, I have read this is due to a battery fault and after trying everything else suggested, it would to be seem correct. I have tried restore mode, DFU mode and editing the HOST file.
The iPhone only powers on when connected to power which to me is the reason for it not restoring. I have tried different batteries that I know work and I have even put the battery it came with in another iPhone, so I know the battery is not at fault!
The battery connector looks to be completely attached and not messed with so this is not to blame either, the water indicator stickers are white so it has not been water damaged either.
I am at a loss at what is wrong with it :( I would guess that it is either the logic board or the Dock connector but I would like other opinions on this.
Later today I am going to replace the Dock connector board with a fully functioning one to see if this makes any difference, I did notice it was full off junk but I removed all of this with a tiny pin so that the USB cable could plug in properly.
I will comment my results once they're known, any help would be appreciated :)