820-2936a missing pp5v_s3

[2informaticos]

Try other chip then...

 

[Kyle93]

Replaced chip with and have new voltages but still no fan spin. new chip getting hot.

pin 13 3.42
pin 16 12.60
VREG 3 3.46V
VREG 5 0.771 V

pp5v_s3 0.632V

what to try next?

 

[dukefawks]

VREG5 is probably shorted to GND causing the chip to heat up. Check resistance to GND.

 

[Kyle93]

Should I assume there is a short inside the board at this point?

VREG 3 resistance to ground is 0.030 even with a new u7200 attached. Once removed resistance to ground is 0.485 Have tried multiple chips

 

[Kyle93]

Replaced everything on VREG 5 line and resistance to ground is still 0.036. Is this unrepairable? If not what else to try or check?

 

[Kyle93]

please respond on what to check for next?

 

[Kyle93]

resistance to ground is now 0.412 so short to ground is gone but u7200 still getting very hot. pp5v_s5 only 3.321V

 

[2informaticos]

Start from zero...
Disconnect everything from the board; leave only magsafe connected, nor even RAM is needed.
If U7200 gets VIN and EN0, it should generate VREF, VREG3 and VREG5.

If ENTRIP2 has 0.75V, PP3V3_S5 should also appear.
Both EN0 and ENTRIP2 are controlled by SMC_PM_G2_EN; so should appear at the same moment.

If ENTRIP2 has 0.9V, PP5V_S3 should also appear.
This is controlled by PM_SLP_S4_L.

Low voltage at VREG5 can only be caused by U7200 itself, or external component sinking to much current.
Start removing chips connected there.
R5805 will isolate U5805 area.
Q7840 will separate PP5V_SUS; you can also check for short directly there.
C7273, near U7200, need to be removed for checking. Also U/C7801 need remove to check.