Macbook Pro A1286 Uni 2008 Not turning on! did 10 seconds Powbutt was working fine

Discussion in 'MacBook Pro' started by dssence, Nov 8, 2013.

  1. dssence macrumors newbie

    Nov 2, 2008
    I got an unibody 2008 Motherboard 820-2330-A. I do take al precautions knowing how thermal cycles affect the solder joints. So my computer was in such a position that the lid had perfect airflow for the fans. In fact I had all the fans both at 5900rpm. I was running Windows 7 natively.
    So I used my macbook plugged in on AC with the removable battery. And honestly i never swtiched it off . But at times when the electricity went off it was the only time the battery drained entirely and turned off.
    Now what started happening was that once that happened the lap would not turn on. I searched all over the net and someone at Ifixit said you had to press power button for 10 seconds.. plug magsafe keep pressing it for 10 seconds more.. depress and press again . To my astonishment that made it work.
    Now , I never really cared much about that..didn't pay much attention .. thought it would be something that might happen a couple of times.
    But now I dissasembled it to clean the heatpipe radiator fins I disconnected the fans vacuumed them and then IT DIDNT" START! I folllowed the exact sam eprocedure as before.
    SO what should I do , I managed to get the schematic for my motherboard. I thought about doing a manual SMC reset on the mainboard but the schematics don't tell me the exact location of the SMC reset pad which is 5001. Do you have by any chance the .brd file of this motherboard? Thanks for your help. Some thoughts

    - On some places said if the sensor on the heatpipe it's broken it wont turn on (I checked it and it's connected ok)

    -I did the 10 seconds procedure on the power on buton.. keep pressing then connected magsafe 10 seconds more .. Nothing ( This worked before) But it worked on the scenario when electricity went off, machine drrained compeltely with removable battery.
    then I took battery and did that procedure.

    - I managed to check the Power On pins on the logicboard , bridged them .. Nothing!

    -I checked the Power button to see might be stuck, disconnected the keyboard flex. found pin 5 bridged it to ground nothing.

    -This laptop never exceeded 60 degrees, I had it run windows7 with fans full blast with lubbos at 6000rpm. And was alway on , no thermal cycles. so it wasn';t exposed to vulnerable solder cracks because of thermal cycling.

    -I DID FIND ! A SMALL RECHARGABLE BATTERY ON THE LOGIC BOARD which was in bad condition like as mall button cell which was soldered and said F8430 on top. i'm thinking this might be the reason some times the other procecure worked but I don't know what voltage this button cell is
    Picture for the button cell is on this link

    I'm hoping you can help me out, I'm really sad
  2. dssence thread starter macrumors newbie

    Nov 2, 2008
    Well I've checked on the schematic and it's the RTC . Supposedly it's defined as Super capacitor C2800 but the format it's the same as a button cell. So it doesn't look like a cpacitor at all. I was worried about this supercap or battery whatever. Cause I've fixed lot's of notebooks before which seemed dead, and I just removed the cmos battery shorted to reset it and it came back to life. So I thought this might be going on here.. this cap/battery might have drained entirely rendering an SMC kind of reset line issue.
    Do know that I also did a manual SMC reset from the logic board pads, and same thing. Another thing there's an IC from intersil ISL6269 (U7750) which is running extremely hot to the touch, even without pressing the power button. I just had the logicboard out of the case just with the magsafe board plugged psu and it was burning hot to the touch.
    Some other insights. I measured G3hot voltages and Always voltage on power rails and I do have 3.4v on Power on PAD , something to notice is that when I press the power on button that voltage goes down to 0.880 from 3.4 if it's of any help. 12 volts rails are there. I did also reflowed the solder on the EFI chip just in case as I've found one guy on youtube saying solders were dry , but nothing.
    Something to do have into consideration is , I do repair notebooks as well and I'm used to GPU BGA's to be desoldered cause of cracked solder joints and thermal cycle stress. So my macbook in question , always had fans at a full speed 5900rpm.. the lid was in such an angle that airflow was precise. I can't believe any of the bga's might have desoldered from the board.
    Something I would really love is to understand all the power on sequence, where to measure voltages and trace this indepth. But I don't have the experience of dealing with the power on states and which signals should go where it's kind of confusing on apple schematic I would need some help here.

    Again thanks !



    a couple things here..

    1) I haven't tried this system with a completely new magsafe PSU ( though voltages are fine ) could it be screwed up not giviing enough juice current?

    2) I've already suspected that PWM chip from intersil might me bad ( though this chips are made to work at hgh temps it's not normal being freaking hot to the touch). So I've ordered a couple samples from intersil.
    Should I desolder the qfn and solder a new chip there?

    3) It might as well be the reason the FAN it's being shorted. I've been using this macbook always with Bootcamp Windows 7 Natively, running lubbos fan controller . Cause on Windows 7 the SMC fan control didn't work as it should. So Im suspecting this has to do with SMC controller. Now... the system I know it's not on .. cause I don't hear the HDD spinning neither the screen backlight is on .. so something could be shorting the fan.
    What do you want me to check ? Advices if it was you.. here.

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