Well after my baseband chips failed on my iPhone 3GS 32GB, I purchased another water damaged iPhone 3GS 32GB.
It was stated as no backlight and booting to apple logo and SOMETIMES going to slide to unlock screen,

Anyway I receive the phone and its totally dead, no power no nothing.

I opened the phone, removed the EMI shields and carefully cleaned everything with acetone. There was very little corrosion on the board itself. But both water indicators are pink.

I checked the main green fuse/resistor for continuity and passed.
Then i checked the little charging link by the doc connector for continuity with success.

I put the water damaged logic board into my other iPhone with working screen and all connectors.
It has no power!

What pins to I check from the doc connector for no power? What IC do I test/check?

Failing that, how do I externally charge the iphone battery as maybe just the charging circuit is dead but the phone may power on with a charged battery (my battery is fully dead after 6 months of no use)