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  1. #1
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    820 - 3332 ram issue

    hey guys,

    i have a retina "15 2012 here with a little bit of liquid spill. Signs are there that the board shorted and got really hot ( some squeezed out balls on 2 or 3 very small chips)

    It came in dry. fan spin, 3 beeps again and again forever. ram voltages seem fine.

    after ultrasonic it once chimed. I put away happily to install it later. So, 3 hours later, when I wanted to reassemble it, beeping again but maximum twice 3beeps, sometimes powering off before full 3beeps.

    I did reflow the ram but no change. I will post later if it is still shutting off after a few seconds still or if it is back to continious 3 beeps.

    Any ideas how to proceed ? What coukd I check for ? Have no experience with this.

  2. #2
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    Re: 820 - 3332 ram issue

    Run ASD and report if any errors are found.

    Otherwise, it might be crap underneath the CPU or intermittent / bad RAM chip.
    If any of the liquid was near the RAM, change the chips in the vicinity.

    Also what chips did you noticed that got hot?

    Boards like that are a nightmare, you could also go and replace all of the RAM, only to discover the error comes back.
    Voltages are good?

    Good luck with that

  3. #3
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    Re: 820 - 3332 ram issue

    How can I run ASD with no chime and ram beeps ?

    No liquid around the ram chips.

    Nothing got hot in my hands. I saw some squeezed out solder and the person who gave the computer to me told me that when she took it out of the bag, in which it had contact with liquid, the machine was pretty hot.

    Ram Voltage seems fine. Which voltages do you suggest to check ?

    thanks :-)
    Last edited by kiezbengel; 05-20-2019 at 02:38 PM.

  4. #4
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    Re: 820 - 3332 ram issue

    Sorry, read it too fast.

    I had a situation on a 2011 13 inch board, that on cold boot the board would do 3 beeps, but only if the board had a MagSafe connected. If I started it on battery, the board chimed and worked perfectly. I replaced a SMC there before that and perhaps it wasn't compatible or it was somehow damaged. Told the costumer that if it does that, he must disconnect the MagSafe and turn it on on battery only.

  5. #5
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    Re: 820 - 3332 ram issue

    I will try a battery start later but if I remember right it was the same.

    As I wrote in my first post the ultrasonic changed the situation. On a cold boot fan is spinning for 10 to 12 seconds and the machine makes twice 3 ram beeps before the fan stops. If I fire it up again and again the fan spin time goes down more and more. After like 5 attempts it spins 5 seconds. When the fan stops I loose PM_SLP_S5_L.

    PPDCIN_G3H is about 20.3V in the beginning, dropping to 16.66 when the fan stops.
    Last edited by kiezbengel; 05-20-2019 at 02:41 PM.

  6. #6
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    Re: 820 - 3332 ram issue

    I found a short to gnd on MEM_A_A<13>

    I can not find any information if it is possible to disable or remove a bank, or better said the only information I find is that it is not possible. I saw widerstandsproject writing about it.

  7. #7
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    Re: 820 - 3332 ram issue

    When the machine is running, touch each of the memory chips, and see if anyone is getting warmer than the others.
    Otherwise, inject some voltage into MEM_A_A<13> and see what is getting warm.

    About the bank disabling, I haven't seen anyone do that. Best thing is to replace the memory chip, if you find one that is bad.
    Last edited by mitchW; 05-21-2019 at 07:57 AM.

  8. #8
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    Re: 820 - 3332 ram issue

    yes, injection was my plan indeed. Chances are that the cpu gets hot.....lets see

    What would be the expected behavior on a running board if one removes one ram bank ? Will it just go beepbeepbeep?

    If I can remove the short and the board still shuts down after a few seconds I might have another problem in addition, right ? I really hope my crappy ultrasonic cleaner didn't fck up pch connections or so

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    Re: 820 - 3332 ram issue

    hey Mitch, hey guys,

    today I injected 0.7 V and was consuming about 0.6A but nothing, really nothing warm to find. Neither any RAM chip nor the CPU.

    Is my only way to proceed to remove one chip after another ?

  10. #10
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    Re: 820 - 3332 ram issue

    This is going to be a hard one. Perhaps try to increase a voltage a bit, but don't exceed the usual voltage on that rail (I forgot what is it supposed to be at the moment).

    I would leave it without heatsinks on for good dozen minutes and check what is happening.
    This is about 0.4W with that voltage and something should be at least slightly warm. Check all the RAM chips, and even CPU.
    If really nothing is getting hot, then you could have a short inside the board itself, or it is a component that is very good in sinking the heat. Sometimes I also cooled the board down in a fridge and then immediately injected the voltage after taking it out.


    Otherwise, your only way is to remove all the components that share this data line, starting with the most possible candidates first, so first remove the chips that got hit by the water, then proceed to others.

 

 

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