820-00034-A 2 led on, fan on, no chime/screen

[2informaticos]

You've said to had steady 3V3_S5; why did you change Q7610 then?
Is not possible to get correct L7610 voltage, if Q7610 was bad.
Good 3V3_S5 implies P12V_S5 was also good.
Now you lost 12V_S5; not sure what you did...

 

[yair37]

i know, i was just check voltage at U7600 area and then the light was off and there was a short on Q7610 i was replace it and now this is the situation..no light and 12v_s5 is 3v

 

[yair37]

i was replaced U7600 all the surrounded components look o.k...where to start?

 

[2informaticos]

Check diode mode to ground at PPBUS_G3H and L7610/50.

 

[yair37]

did you mean PP12V_G3H? PP12V_G3H is present 12v
L7610 - 116
L7650 - 150

 

[2informaticos]

I forgot is an iMac; 12V_S5 in this case.

 

[yair37]

12V_S5 - 100 diode mode

 

[yair37]

the bypassed Q6970 D-S was bad, now 12V_S5- 16V too high? and still no LED

 

[yair37]

o.k we back to 1# LED on.
U7600
17-REG_VIN_U7600 16.6V
18- PP5V_S5 6.7V
4-REG_VCC2_U7600 6.8v
5-REG_VCC1_U7600 6.7v
24-PM_EN_REG_P5V_S4_R 0.01V diode mode 450
12-PM_EN_REG_P3V3_S5_R 11.7V

 

[yair37]

yes it was bad battery
U7600
17-REG_VIN_U7600 12V
18- PP5V_S5 5V
4-REG_VCC2_U7600 5v
5-REG_VCC1_U7600 5v
24-PM_EN_REG_P5V_S4_R 0.01V diode mode 450
12-PM_EN_REG_P3V3_S5_R 8.4V

 

[2informaticos]

You should get correct 3V3_S5 now.

 

[yair37]

yes i have 3V3_S5, how i get the second led?

 

[2informaticos]

Trigger SMC_ONOFF_L and check for pulse at PM_SLP_S4L, at same time?
I hope first LED is stable.

 

[yair37]

#1 led is stable.
PM_SLP_S4_L 0V diode mode 410

 

[2informaticos]

I said to check totally different thing...

Be sure first LED stays on (not flashing), when trigger SMC_ONOFF_L.

 

[yair37]

no pulse...PM_SLP_S4_L 0V stable..
first les stable too...not fleshing.

 

[2informaticos]

Check for drop pulse at PM_PWRBTN_L, at same time when trigger SMC_ONOFF_L.

 

[yair37]

PM_PWRBTN_L 3.3v when i trigger SMC_ONOFF_L, PM_PWRBTN_L down to 0.04 and stay there..not go back to 3.3v