820-4924 not charging

[PPVCC_S0_CPU]

Originally it gave 3 beeps on start up, so reflowed ram chips and it started working, but now when i connect genuine magsafe it doesn't charge or there's no green light, but if i connect aftermarket magsafe, there is green/amber light but battery doesn't charge.
Can anyone tell what could be wrong with it? And what's the ideal resistance between pin 17/18 and pin 28/27?

 

[2informaticos]

Seems that you have some leakage on input circuit.
Original charger detects that and doesn't power up the board.
It has a processor for this job.
Fake chinese charger doesn't have such processor and will always have full voltage output.
Original MagSafe2 charger has only 3V output first, at low current.

This issue is usually caused by Q7180.
Check R7180/81 and R7185/86 values onboard.
Also check if D7010 is OK.

 

[PPVCC_S0_CPU]

It was bad dc in board, now green light comes and computer runs on battery but it doesn't charge(it charges but doesn't show charging sign, but i can see percentage going up).
one thing i noticed is that it charges with charging sign in recovery mode, but doesn't show charging sign in normal mode.
resistance between pin 17/18 is around 3 ohms and between pin 27/28 is 20ish ohms.
checked smbus resistors and they are fine and gets 3.3 volts on them.
acok is present, charger reset is present.
upon further inspection i found that pin 19 and 20 was getting 2.3 volts instead of 5, it was short on pin 20, so i replaced it and it went back to 5 volts but battery still doesn't charge.

is it possible that this short may have destroyed battery?

 

[2informaticos]

I recommend you to test other battery first.
You can waste time digging in the MLB having bad battery.
Post voltage for pins 9 & 15 of U7100.
What tells OSX about battery in System Report?
Does the machine start on battery only, without charger connected?

 

[PPVCC_S0_CPU]

I recommend you to test other battery first.
You can waste time digging in the MLB having bad battery.
Post voltage for pins 9 & 15 of U7100.
What tells OSX about battery in System Report?
Does the machine start on battery only, without charger connected?

there are no voltages on amon and bmon, and is there suppose to be any voltage on pin 1 and 26? i don't get anything there.
it starts from battery only

 

[2informaticos]

Pins 1 & 26 should be 0V, is correct.
Pins 9 & 15 should have some voltage, less than 1V; post the exact values!

Please, do NOT quote an entire post from 5cm above...

 

[PPVCC_S0_CPU]

It was ssd, used different ssd and it started charging.
thanks for the help.

 

[PPVCC_S0_CPU]

Okay, so back to square one, it started giving 3 beeps on start up again.
i have already reflowed ram chips, so is there anything else that i can do?

 

[2informaticos]

I recommend a good ultrasonic clean...
I hope used quality flux for RAM reflow.

 

[PPVCC_S0_CPU]

I hope used quality flux for RAM reflow.

Yes i used good flux, it works for 2-3 days and then it starts beeping again. I am planning to replace ram chips.
can i use ram chips from any donor board or do i need exact same board for ram transplant? And where can i buy stencils for reballing? I don't know what type of stencils are used for reballing these chips

 

[2informaticos]

Reballing RAM chips should be good enough.
Your problem should be generated by crap/corrosion under chips, not internal issues...

You can use any compatible chips, in case still want to change them.