Hello, i have a 820-3115-B that initially didnt turn on,
First there was corrosion on C7528, i replaced it but pin 1 was gone from the corrosion so i ran a wire from pin 1 to pin 1 of C7523
PPBUS_G3H was 1V and i located a short on C7121. After replacing C7121 there was fan spin.
After assembling the mac and turning it on it chimed and LCD turned on. Then it suddenly shut off.
After that it no longer turned on and it only has quarter fan spin.
R7402/3 are both good and U7400 looks great .
First there was corrosion on C7528, i replaced it but pin 1 was gone from the corrosion so i ran a wire from pin 1 to pin 1 of C7523
PPBUS_G3H was 1V and i located a short on C7121. After replacing C7121 there was fan spin.
After assembling the mac and turning it on it chimed and LCD turned on. Then it suddenly shut off.
After that it no longer turned on and it only has quarter fan spin.
R7402/3 are both good and U7400 looks great .