Logic board part number: 820-3437
| Problem | Solution |
|---|---|
| Random shutdown | Visual inspection: can be caused by corrosion at U7090 (makes PP3V42_G3H), corrosion at BIOS chip, several bad probe points and capacitors Example: https://www.youtube.com/watch?v=z_N23fNAgpw (U7090 replaced, several capacitors replaced and probe points revived) |
| Boot Loop | from 10 mA to 550 mA several times then settling at ≈350 mA Thermal camera showed U4500 was bad due to liquid damage |
| No green/orange light on charger |
REMEMBER: SMC is not on if PPBUS_G3H is 8.15 V instead of 8.55 V (SMC needs to communicate with U7100 to tell it over SMBUS line to raise PPBUS_G3H from 8.15 V to 8.55 V). |
| No power, PM_SLP_S4_L is missing, draws 23–24 mA of current |
Example: https://www.youtube.com/watch?v=rAHLji04zOo (fixed by running jumper wires to bypass corroded probe points)
Example: https://www.youtube.com/watch?v=1CqYQWdo6XE Power Rails PPBUS_G3H (8.6 V), PP3V42_G3H (3.42 V), PMDSW_POWERGOOD (3.3 V), PP5_VS5 (5 V) were checked. Corrosion at U1900 (Real Time Clock — RTC). RTC chip was replaced and this fixed the computer.
If PM_SLP_S4_L missing, we need to check these
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| No power, 0 mA draw or 250 mA draw, PPBUS_G3H missing | Short to ground on PPBUS_G3H. Blown fuse F7140 for PPBUS_G3H (if it draws 0 mA), or good fuse (250 mA), bad tantalum capacitor on PPBUS_G3H. |
| No power, power cycling 200 mA / 20 mA | Check U8005 and C8005 Check corrosion around Y1915. PP1V05_S0_PCH_VCCACLKPLL continuity to other side can be missing. |
| No backlight |
Can also be caused by cracked L7701 pin, check with ohmmeter. |
| No power, PPBUS_G3H 4 V instead of 8.55 V |
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| Any board-level issue at all. | Look at J6100, and feel guilt-free in killing it. |
| Keyboard and trackpad not working |
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| SMC_RESET_L low, but board works outside of case | Bad trackpad. Trackpad controls SMC_LID and SMC_RESET_L, so trackpad can mess with backlight. Louis explains here |
| Battery not recognized with X | Firstly, try a known good battery before assuming it is the board! If PPBUS_G3H is 8.15 V, SMC is not communicating properly with anything because its data line is blown. Check pull-up resistors on data line, see what may be pulling it down, most likely bad SMC (U5000). |
| Not powering on but is charging |
Take note that on this board if you remove the battery, when turning on the board you should expect the fan to turn on/off/on/off/on. If you have a problem with the clock the fan turns on continuously. Example: https://www.youtube.com/watch?v=lHJe8g52rSo |
| Braindead |
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| Smoke coming from SSD connector |
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| USB issues |
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| Not powering on | Corrosion around JTAG connector and 5 V regulator circuit. Example: https://www.youtube.com/watch?v=OwiKfiG7Aas
PRAM needs to be reset. Example:https://www.youtube.com/watch?v=IVgKJF_dIy0
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| You think PPBUS_G3H is 8.55 V | You measured the right side of the fuse, not the left side of the fuse, because you are right handed and keep the red probe of your multimeter in your right hand. Had you measured the left side of the fuse, you'd realize the fuse is blown, likely due to a short circuit. You are probably off in the wilderness, hunting why your PP3V3_S5 and PP5V_S5 are missing, before you even have PPBUS_G3H... we've all been there. |
Laptop does not power on or Laptop does not power on, quick power spike before settling around 25 mA | Look for corrosion on the U7400 chip on the logic board and replace it Example: https://www.youtube.com/watch?v=-rok8h1ZRH4 (820-3437 logic board repair with new video format) No liquid damage, the U7400 chip has a 5 V input on pin 12 and a 1.5 V output on pin 2. If the board does still not power on you might want to check for a short between pin 3 and 5 to 8 of Q7430 as it can fail due to oxydation on it's brain (U7400) |
| No Camera (Please do not fix unless required) | Different issues
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| Not booting, all >S4 rails cycling | At the end of the power sequence, there should be activity on pin 1 of U6100 (SPI_MLB_CS_L). This rail also wasn't being pulled up to 3.3 V either. This machine was liquid damaged so after replacing U1900, U6100 and termination resistors, this pin was still low with no activity. Problem was an open circuit track between R6110/R6120/R6125. Used a jumper between the SPI_CS0_L test pad and R6110. No visible damage noted so open circuit was an inner layer problem. |
| Fan spins on then off then on then increases speed, no boot with board out of case or keeps turning on off on off repeatedly with board in case and battery connected | CPU_VCCST_PWRGD measured as 0.33 V, bad U1930 |
| No WiFi |
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