820-3588 not turning on.

donnos

Member
Got an iMAC where the first LED Blinks on button press but not turning on.
Its not Q8450 and i have steady 12V
I'm not getting pm_slp_s4_l and not pulsing either.
is the criteria for s4 en same as macbook?
 

2informaticos

Administrator
Staff member
If S5 LED blinks when you press power button, means that 3V3_S5 is not steady.
So, do you have at least 12V_S5 steady all the time?
If not, check around Q/U6970.
Be sure 12V_G3H is stable.
 

donnos

Member
i meant that i have 3.3V for 3v3_s5 and 12v for 12v_s5 up till when i click the the power button and it blinks.
means voltage drops to 0 for both lines and go back to 3.3v and 12v shortly after
 

2informaticos

Administrator
Staff member
"Be sure 12V_G3H is stable."
If not, change power supply.

Check for short on all big coils.
Try to start in SMC bypass mode.
 

2informaticos

Administrator
Staff member
Press and hold power button.
Insert power cord (previously removed) and release power button after 5-10s.
Then press power button again (shortly).
 

donnos

Member
didn't know smc bypass works for IMAC as well.
well this time the LED didn't blink but stayed lit all the time. still no boot
 

2informaticos

Administrator
Staff member
Check for pulse at PM_SLP_S4_L, triggering SMC_ONOFF_L in SMC bypass mode.

See if all PCH's signals are present.
 

donnos

Member
1. PPVRTC_G3Hx (VCCRTC) PP3V3_G3_RTC
2. RTC_RESET_L (RTCRST#) RTC_RST_L
3. PCH_SRTCRST_L (SRTCRST#)
4. PCH_INTVRMEN_L (INTVRMEN)
5. PCH_DSWVRMEN_L (DSWVRMEN)
6. SYSCLK_CLK32K_RTCX1 (RTCX1)
7. PP3V3_S5 (VCCDSW3-3)
8. PM_DSW_PWRGD (DPWROK)
9. PP3V3_SUS (VCCSUS3)
10. PM_BATLOW_L (BATLOW#)
11. PM_RSMRST_L (RSMRST#)
+1. PM_PWRBTN_L (PWRBTN#)

checked all this and i have 3.3v for all this. no pulsing on pm_slp_s5_L or pm_slp_s4_L. i'm thinking dead PCH
 

2informaticos

Administrator
Staff member
"6. SYSCLK_CLK32K_RTCX1 (RTCX1)"
I suppose you've meant PCH_CLK32K_RTCX1.
3V there for sure?
In such case, other reason for bad PCH.
Should have 32KHz sine wave there.
 
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