820-4924 Green/Amber light ? No Power

Bad Apple

New member
Green Amber light ok ? No Power, No corrosion, No spill, Clean board. Customer claims it simply refused to start.

Sorry if it seems I am all over the place....still at an early stage repairing boards and I've been trying whatever I could find searching the forum.

I tested the following Rails and test points but am at a standstill. Any advise where to test next ....TIA
  • PPBUS_G3H @F7140 = 12.5v
  • PP3v42_G3H @C4850 = 3.4v
  • PP5v_S5 @C8060 = 5v
  • PP5v_S4 @L4803 = 0v
  • PP5v_S3 @C4690 =0v
  • PP5v_S0 @L4010 = 0v
  • P5VS4_EN @C8192 = 0v
  • PP3v3_S5 @C8000 = 3.3v
  • PP3v3_S4 @C4830 = 0v
  • PP3v3_S3 @C2031 = 0.175v
  • PP3V3_S0 @C6600 = 0v
  • PPVCC_S0_CPU @C1097 = 0v
  • PPVCOMP_S0_CPU @R0530 = 0v
  • PM_SLP_S3_L @R8178 = 0v
  • PM_SLP_S4_L @R5170 = 3.4v
  • PM_SLP_S5_L @R8115 = 0v
  • PPVRTC @R1450 = 3.3v
  • PPVRTC_G3 @C1910 = 3.34v
  • Smc_onoff_L @R4810 = 3.3v
  • SMC_RESET_L @ R5100 = 3.4v
  • ALL_SYS_PWRGD @R8164 = 0v
 

2informaticos

Administrator
Staff member
Do NOT waste time checking S3, or S0 voltages when already found a missing S4 voltage.
I was waiting to read 3V3_SUS voltage, much more important.

"PM_SLP_S4_L @R5170 = 3.4v"
Misstyping, or looking wrong schematic?
PM_SLP_S5_L should be released first.

Did you try SMC bypass mode?
Post PM_BATLOW_L, PM_RSMRST_L, PM_PWRBTN_L.
Trigger SMC_ONOFF_L and check for reaction (drop pulse) at PM_PWRBTN_L.
If exists, all PM_SLP_Sx_L signals should pulse at same time.
 

Bad Apple

New member
Hi 2informaticos,

Thanks for the tips, and yes it was a mistype. Actual reading is .... PM_SLP_S4_L @R1461 = 0v

PP3V3_SUS @R1581 = 3.3v
PM_BATLOW_L @R1410 = 3.3v
PM_RSMRST_L @R8133 = 3.3v
PM_PWRBTN_L @R1802 = 3.4v


No reaction at PM_PWRBTN_L when short SMC_ONOFF_L @R5115

I did get a pulse when triggered SMC_RESET_L - 0v to 3.3v
 
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2informaticos

Administrator
Staff member
What is the reason to trigger SMC_RESET_L???

Check the 4 (four) RTC signals at page 12.
Also check PCH_DSWVRMEN and PM_DSW_PWRGD.
Do you get 3.3V at SMC_ONOFF_L?
 
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Bad Apple

New member
I am confused about how to do an SMC bypass. I found something about triggering the smc_reset_L and thought that might be the way.

Can you give me a hint how to do the SMC bypass? Not finding anything about how to do it, just chatter about doing it.

PCH_CLK32K_RTCX1 @ U1900 = 0.376v

PCH CLK32K RTCX2 (Not seeing way to test)

PCH_SRTCRST_L @R1300 = 3.3v

RTC_RESET_L @R1303 = 3.3v

PCH_DSWVRMEN @R1450 = 3.2v
PM_DSW_PWRGD @R1451 = 3.4v

Yes I get 3.3v at SMC_ONOFF_L
 

Bad Apple

New member
PCH_INTRUDER_L = @R1301 = 3.0v

PCH_INTVRMEN @R1302 = 3.2v

Thanks, I will reball SMC tomorrow

It would be a big help for future diagnostic if you could advise on How to do an SMC Bypass.
 
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Bad Apple

New member
I was finally able to get time to do the reball. Sorry for the delay in responding but I am alone dealing with clients and the repair work.

The SMC reball did not change anything. It was clean.

It sure would have been nice to have tried an SMC bypass first, but It seems that is a closely guarded secret.
 

Bad Apple

New member
No I was not joking. I searched for SMC Bypass for over three hours only finding chatter explaining suggesting doing a bypass, but nothing on how to actually do it. I found this by accident while searching another problem I'm having with a MBA that has a battery issue. https://www.tech-g.com/2015/04/15/ma...ttery-problem/

How to do an SMC Bypass

To bypass the SMS and make the computer run, you do the following

1- Disconnect the power cable.

2- Hold down the power button for 10 seconds (or more), then while still holding the power button down, connect the power cable and keep the power button pressed down for another 10 seconds (or more), then once the 20 seconds are over (10 without cable and 10 with cable), release the button and press it again like you normally would to start the computer.

Maybe this could save someone else a bit of time

P.S. it only worked for me with the battery disconnected
 

2informaticos

Administrator
Staff member
Yeah, why should you need to hold the button 10s, if power is already disconnected?
Just press the button, connect charger and keep pressing 5-10s.
Usually starts in 5s, keep pressed untill 10s, just in case.
Once started, release the button.
You can use the power pads from MLB, instead of power button, when the MLB is on the desk alone.

So the MLB works in SMC bypass now?
Do you get AVREF_SMC?
 
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