820-2530, strange voltages on U7200

[Mrit]

I have a board with all of the G3H powerails present, but on of the S5 rails present.

I have the following measures from U7200:

Vin (pin 16) =12.61V;
Vref(pin 3)= 0V;
Vfb2(pin 5) = 285mV;
Vreg3 ( pin 8)= 260 mV;
Vreg5 (pin 17)= 17mV;
Veno(pin 13)= 14mV.

Is this indication of a bad U7200?

How do I go further testing and diagnosting?

Thank you for your time.

 

[2informaticos]

What about pin 13/U7200?

Just in case, check diode mode to ground on VREG3/5 outputs and L7220/60.

 

[Mrit]

Thank you for ypur reply.

Please find below the info requested.


V en0 (pin 13) is14mV;

In diode mode,
VReg3 = 0
VReg5 = 0
L7220 (pin 1 and 2) = 0.60V.

What do you mean by L7220/60, exactly?

 

[2informaticos]

"VReg3 = 0
VReg5 = 0"
Do you really have both shorted to ground?
You may want to say OL, but I'm not sure.
However, in diode mode (red probe connected to ground), you cannot get 0 (zero) reading there, nor OL.

"L7220/60"
L7220 AND L7260...

 

[Mrit]

Yes, sorry, my bad.

I meant,
In diode mode,
VReg3 = 0L
VReg5 = 0L.

Also, in diode mode L7220 is 0.601 and L7260 is 0.449, both measured to ground.

Also, I have to mension that cap C7280 is missing, but the pads/ traces around it position look ok.

 

[2informaticos]

Should be good to replace C7280.

You must get some indication on VReg3/5, if you measure diode mode with red probe connected to ground.

So you have missing SMC_PM_G2_EN.
This could be SMC issue.
Do you get green light on magsafe?
Be sure to use 60/85W original charger.

 

[Mrit]

Yes, I have the green led on the charger jack.

I think SMC_PM_G2_EN is fine. I measured voltage between pin 1 of R7273 and ground and I get 3.401V. But on pin 2 of R7273 the voltage to ground is 14 mV. I also checked resistance 7273 and I get 43.1kohm, as opposed to 95kohm from a board where U7200 is functioning properly.

 

[2informaticos]

Change U7200...