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

[jadao]

Hi vaswaniraj,
Are you sure your voltmeter mode is not set to a lower range? Something like 0-5V?
Autorange? Check with a 9v battery and see if you still have OL.

 

[vaswaniraj]

Hi Jadao, Yes you were correct. My sincere apologies, I was not setting my range correctly. Instead of setting it to 00.00, I was setting it to 0.000 due to which any component that I was measuring I was getting .OL.

Ok so now PPBUS_G3H is present and PP3V42_G3H is also present.

Further troubleshooting steps please. I will be very honest, in my life I have never used a multimeter, I am sorry for the errors that I have doing so far. But after this I know that I will not make this kind of error.

 

[dukefawks]

So what is the voltage on PPBUS?

 

[vaswaniraj]

voltage on PPBUS 8.60V.

 

[dukefawks]

Was this liquid damage?

 

[vaswaniraj]

Yes it was liquid damaged and the customer changed the keyboard and trackpad himself, after which it worked for almost 9 months and then it shut down on him.

 

[dukefawks]

Voltage on L7560 and L7520? Did you check for corrosion around U6100 and U1950?

 

[vaswaniraj]

Hi Duke, The voltage on L7560 = 3.33V

The voltage on L7520 = 0 V

I don't see any corrosion around U6100 and neither on U1950.

Is L7520 supposed to be 0V ?

Because from the schematics I see it, should have 5V.

Please advice.

 

[dukefawks]

Check board for corrosion, it must be somewhere.

 

[vaswaniraj]

Hi Duke, I looked over the complete board, but I don't see any corrosion. The only green corrosion is see is by the SD Card reader. Some of the probe points I see are dark red, few are green and most are yellowish. Would a ultrasonic clean help ?

 

[dukefawks]

Give it a clean, won't make it any worse.

 

[vaswaniraj]

Ok let me try giving a ultrasonic clean. Will get back to you.

Around how much time should i put it into the cleaner and at what temperature.

Please advice.

Raj.

 

[dukefawks]

I have no idea depends on which machine you have and what liquid you're using.

 

[vaswaniraj]

I have Crest CP500D and I use Branson EC with Distilled water.

 

[dukefawks]

5-7 minutes or something.

 

[vaswaniraj]

Ok, Thanks Duke. But troubleshooting wise you don't see anything wrong ? I was watching one of the videos of Louis where he has mentioned that PP5V_S0 is not present and then the computer will not come on. I checked the voltage on U8180 and it shows 0 ( Zero Volts ) Do you think I am going in the right direction ? Please advice.

 

[vaswaniraj]

Hi Duke / Louis, I Ultrasonic the motherboard, the components are all clean and shiny, but still the fan does not spin. When I connect the logic power to the magsafe adapter, the light stays orange, but the fan does not come on. I checked the following rails and here are my findings.

PPBUS_G3H = 8.59 V
PP3V42_G3H = 3.33 V
PP5V_S5 = 5.02 V
PP5V_S0 = 0.00 V
PP5V_S4RS3 = 0.00 V
PPVRTC_G3H = 3.33 V
PPDCIN_G3H = 16.51 V
PPDCIN_G3H_ISOL = 16.51 V
PPDCIN_G3H = 16.51 V

From the above I see that I am missing the voltages on PP5V_S0 and PP5V_S4RS3.

How can I get the 5V on these power rails.

Is it because of the 5V rails as mentioned above having 0 V the computer is not coming on and the fan is not spinning.

Can you please help me with the further in troubleshooting.

Regards, Raj.

 

[dukefawks]

Could be anything. The usual suspects are U6100 and the resistors in the data lines, U1950 especially pin 8 and U1900.

 

[vaswaniraj]

Hi Duke, As per your advice I checked all the resistors in the data lines and none of them are short to ground. Where else should I look for troubleshooting. I even tried to watch some of the videos of Louis in relation to 82-3437, but still am unable to solve the motherboard and make it turn on. Please help me troubleshoot further. Louis, your interference is required, if you don't mind. Thanks Raj.