I got a water damage 820-3115 that doesn't boot up. It has a green light on the charger (PPBUS_G3H 12.57v , PPDCIN_G3H 17.08v, PP3V42_G3H 3.46v) and 3.42v on SMC_ONOFF_L pads. After doing some visual inspection I noticed that that the FireWire port power switch circuitry is f*cked. Its missing Q4262 & F4260. Would this circuitry prevent the computer from booting up? From what I can see, 5v_s3 and 3v3_s3 are missing. Should the s3 state be present when the computer is off?
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Pp5v_s3
- Thread starter elcapitan
- Start date
Thanks duke!! I have re-checked 5V_S3 and its shorted to ground. I tried injecting some voltage (no more than 3v) into this line but it's hard to determine the faulty component since it only consumes 0.18A at 3.0v. I noticed that is getting a little bit warm u4800. Should I add more voltage? Any recommendations? Thanks!
I have managed to remove the short by removing u4800 but now when I connect the charger to the computer, the short on 5v_s3 appears again and then disappears. Please note that I haven't replaced this chip. Is this chip important? From what I can see it's usb peripheral controller chip . Thanks for all the help
U4800 is not needed. U4800 will only fry when the 5V bus has been high. There will be more components dead that are on this bus usually the ISL chips that get their 5V from this bus.
And no the short does not appear again, you are measuring when there is still some voltage left or measuring when powered on even!
And no the short does not appear again, you are measuring when there is still some voltage left or measuring when powered on even!
Thanks for the clarification duke!! At the moment my board is missing 5v_s3 and this line is not shorted to ground. My Meter on diode mode with red probe on gnd and red probe on 5v_s3 gives me 0.430 I tried to see to see if the computer would turn on by injecting 5v into this line. When I did this the fan spinned for a second and my PSU got stuck at 0.24A and 5v. Not sure what's going on here. Is my u7200 fried?
Should I measure it when I'm inject 5v into 5v_s3?
hello duke, you are correct I'm also missing ALL_SYS_PWRGD. I'm a little bit confused thou! Hopefully you can clear up some things. At the moment I don't have 5v_s3. I tried injecting 5v into this line to see if the computer starts up and it consumes 0.24amps. I noticed that u7200 is getting really warm when this occurs. I don't understand why there is a consumption on this line if I already removed the short on this line. Any idea? I have proceeded with troubleshooting this ic and I'm getting the following values ENTRIP1 0v, EN0 1.71v, ENTRIP2 0.62v, PGOOD 0.13v, VIN 12.57v . Do you think my u7200 is no good? I checked P5VS3EN_L on point 2 of Q7221 and I have 2.26v. Does this mean my mosfet is not good? According to the schematics it looks like q7221 uses the same mosfet to generate entrip1&2. Please correct me if this is wrongThanks!
JorgePayar
Member
I had the same problem with this board I had no 5V_S3 and it was because of u7200 that was shorted. And as I can see you have the same problem, I would replace u7200
but wait for what Duke says
but wait for what Duke says
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Sorry duke! I couldnt control myself. It seems that u7200 was shorted. When i removed this ic i was able to inject no more than 3 v into this line without any consumption. I think ill Be able to restore pp5v_s3 after replacing this chip. If this is the case ill be a happy guy. Can i salvage this chip from a 820-2879?
JorgePayar
Member
Yes, it is the same chip TPS51125
Do keep in mind that core 2 duo A1278 boards have different orientation on TPS51125 than core i5/i7 boards.
So don't rip it off the 2879 and directly transfer it to the 3115, it will go on fire. make sure you put it back in the proper orientation.
So don't rip it off the 2879 and directly transfer it to the 3115, it will go on fire. make sure you put it back in the proper orientation.
GOOD NEWS!!! After replacing TPS51121 with a donor ic and injecting the 5v into 5V_S3 we have a spinning fan. It's time to find out why I'm missing that voltage. Any idea? If I'm not mistaken this line gets created by u7200 so this should have addressed this issue. I think my q7221 is not opening since is getting 2.26v at the gate.
What's the voltage on pin 6 of U7200?
Hey Louis, here are my readings for u7200 VIN 12.57v, EN0 2.98v, ENTRIP1 0v, ENTRIP2 0.85v PGOOD 0v. Ilex me know if you need any other ones. I have recently changed q7221 but no luck. Thanks for giving me a hand
23 continuity to gnd
JorgePayar
Member
Could you show or tell where the water damage was?
larossmann dukefawks
Can we reppen this post? I just got another board with the same problem and readings. Thanks!
Can we reppen this post? I just got another board with the same problem and readings. Thanks!