[SOLVED]820-3437 - PPBUS_G3H is showing .OL on multimeter

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vaswaniraj

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Hi Guys,
Today I received a Macbook Air 13" which is not coming on. I checked the power rails and found out that the PPBUS_G3H is showing .OL on the multimeter. Now here is what I did. I measured every component where PPBUS_G3H should be present, and it measured as .OL. I understand that .OL means short to ground. Am I correct in saying that ? How do I troubleshoot it further and make the computer work. Please advice. Raj.
 

vaswaniraj

New member
Louis, Ok here is what I am doing. I plugged in the charger and I go on the schematic page to see all the power rails. The first power rail I see is PPBUS_G3H. I go to the board view by Landrex and under "Net" put in PPBUS_G3H, where the board view software point out all the components that has PPBUS_G3H. I put my black probe on the ground and the RED probe on the component that shows PPBUS_G3H. For eg. the board view software pointed on on C3080 and R3080 as one of the few components and C3080 it says there is PPBUS_G3H where i put the RED probe on the Pin 1 and the multimeter reads .OL. I need further help. Please advice. Raj.
 

vaswaniraj

New member
aprendiz. The voltage on PPBUS_G3H is showing .OL. I have my charger plugged in and it is giving me an orange light. The battery is not connected to the Logic Board.
 

aprendiz

Moderator
Well, im not Louis but anyway.........

​​​​​​​i'm asking voltage measurements, i guess you are measuring in resistance mode....
 

vaswaniraj

New member
I replied your question as aprendiz. Louis is online and he asked me some questions, which I responded as mentioning Hi Louis. Anyways. Now answer to your question. I am measuring the above by putting in VDC mode. Is that resistance mode ? Raj.
 

smiba

New member
OL means Over Load, make sure your multimeter is set to a high enough value and is on Voltage.

PPBUS_G3H should be about 12.6V
 

vaswaniraj

New member
Hi Smiba, My multimeter is an Auto Ranging Multimeter which ranges up to 600V 400mA MAX. I am not getting PPBUS_G3H as 12.6V, when I put the multimeter in VDC mode and measure the component where PPBUS_G3H is present, I get OL and not 12.6V. I would highly appreciate if anyone can point out what is wrong I am going so that I can correct myself and learn. Duke, Louis or anyone please help. Regards, Raj.
 

vaswaniraj

New member
Hi Duke, Yes PP3V42 is present. But when i measure the resistor and capacitors on the PP5V_S0 I am not getting 5V on PP5V_S0. Am I going in the right direction, Also on PP5V_S5 when I measure the resistor and capacitors (C7400) and Pin 12 on U7400 the multimeter shows up .OL. I believe that the 5V rails are missing and hence the board is not coming on. Please guide me if I am going in the right direction of troubleshooting. Louis has mentioned to me a couple of times that even if my diagnosis are wrong, I should speak up. I have mentioned in this window what my findings are. Duke / Louis - Correct me if I am wrong
 

vaswaniraj

New member
Hi Duke, when I put my black probe to ground and the red probe to one of the capacitor where PPBUS_G3H should be present the multimeter shows OL. Actually that was my question initially. What is that I am missing to check. Also your question regarding charger light, yes the light is showing Orange because battery is not connected, but if battery is connected, as battery is 100% charged, the light is Green. Please advice. Raj.
 
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vaswaniraj

New member
Hi Duke, could you please explain me how to measure resistance to GND for PPBUS. Sorry, this may be the most basic question that I may be asking, but I am being honest that I don't know how to measure resistance to GND. Regards. RAJ.
 

vaswaniraj

New member
Hi Duke, As advised by not connecting the power and measuring the resistance to ground on PPBUS the multimeter does not show any change. When multimeter is turned on into Ohms, it stays at OL and on measuring the components, R7006, R5501, Pin 4 of Q5500, Pin 2 of R5450 and R5430 there is no change in the multimeter reading and it continues to stay at OL. Please advice further. Basically what does OL mean ? Smiba mentioned on the forum that it mean Overload, I was told by someone it means Open Line. Please advice what is the correct way to interpret OL, and also further troubleshooting this problem. Regards Raj.
 

vaswaniraj

New member
Hi Duke, Forget the multimeter, Basically what am I supposed to check when the meter in Ohms. Let me get this straightened and then I can probably get you a better answer. I see that the multimeter shows 3.42 volts on PP3V42_G3H. If I have to check PPBUS, under Volt DC mode, what voltage should I get. Please advice.
 

vaswaniraj

New member
Hi Duke and Rossmanngroup team,

Let me start this again. Please be patient with me. Here is what I am doing and now you please advice me what is that I am doing wrong. I am trying to put everything in step form.
1. Connect logic board to power.

2. Measure voltage on PP3V42_G3H - All are present. I get 3.44 V on every component where PP3V42_G3H should be present.

3. Measure voltage on PPBUS_G3H - Keeping the power connected. Touch the black probe on Ground ( a screw hole ) and Red probe on the component where PPBUS_G3H should be present. NOW Here I read the voltage on the Multimeter and the screen reads .OL. Every component wherever PPBUS_G3H should be present I get .OL.

Now what does this indicate.

Secondly here is what i did as well.

Disconnected the power adapter from the logic board.

I put the multimeter in Diode mode ( arrow pointing to the right with a small straight line ) and then keeping the RED probe to the ground ( a screw hole ) and the black probe to the component where PPBUS_G3H should be present and the multimeter reads 0.115V.

Does my working above make sense to you. If not please advice me what is wrong I am doing so that I can correct myself.

Thanks and Regards, Raj.
 
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