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820-2850 no image, pendrive doesn't flash, no brain despite vcore present

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  • 820-2850 no image, pendrive doesn't flash, no brain despite vcore present

    No history except that I see some caps for PPVCORE_S0_CPU were touched with solder. Maybe even replaced. Owner said it doesn't produce any image on screen.

    Laptop starts, fans spin, I "think" (went quickly through voltage rail check), that voltages are present. Tried with external monitor, no luck.

    Any point what to check next? Thanks

  • #2
    Try a new BIOS. Keep old one in case that is the issue. If no change, probably going to be a sucky one possibly no fix

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    • #3
      Just tried one. No change.

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      • #4
        Yeah could be anything. Sounds like a bad CPU to me

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        • #5
          Do you get L7630 voltage?
          Also check L7720/60 and Power FETs on page 72.
          ALL_SYS_PWRGD steady high?

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          • #6
            L7630 --------------------- 1.08v
            L7720 --------------------- 1.8v
            L7760 --------------------- 1.2v
            ALL_SYS_PWRGD --- 3.3v

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            • #7
              Did you try one RAM module at a time, different DDR3 speed?
              If someone changed caps on CPU area using hot air, overheating CPU, this board could be trash now.

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              • #8
                Without RAM, there are no beeps (speaker is connected)

                With faster RAM and one slot at a time, no luck.

                *These caps were worked on (see pic)

                **Tiny cap bottom left is fine, but I have aligned it after.
                Last edited by djdblaster; 12-22-2018, 09:02 AM.

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                • #9
                  PP1V8R1V55_S0GPU_ISNS_R should be 1.8V according to schematics. I have 1.33V. Could that be a problem?

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                  • #10
                    Check on the schematic what FBVDD_ALTVO means...

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                    • #11
                      Got it. It's in 0 state.

                      Alright, so any more ideas what could be wrong with the board? Are there any data lines that could be stopping Macbook from booting, just like with an iPhone?

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                      • #12
                        As you've found signs of previous hot air attempts on CPU area, it could be dead now...

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                        • #13
                          PPVCORE_S0_CPU measures around 40 Ohms. Nothing gets too hot. I know there's tons of balls under CPU and PCH, but is there a way to check something that could point in some way/tell something about CPU?

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                          • #14
                            40 ohms is correct value.
                            Doesn't mean CPU should be good...

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