820-4668 No POWER - PP5V_S0 missing

mushr00m

Member
iMac 820-4668 No Power


Only FIRST LED showing up

PP12V_G3H = 12.05V
Replaced the SMC same behavior

Power Rails as below
PP12V_G3H = 12V
PP12V_S5 = 12.05v
pp5v_s5 = 5.1v
PP3V3_S5 = 3.29V
pp5v_s4 = 5.1v
pp3v3_s4 = 3.29v
pp12v_s0 = 12.05v
PP1V2_S3 = 1.18V
pp3v3_s0 = 0v
pp5v_s0 =0v


Replaced U8400 / U8440 / U8420 Still same behavior

When trying to turn on through the PSU injecting 12V on it. It goes to 0.180a and back to 0.049 and keep stuck at it
 

mushr00m

Member
u8500
1 3.28
2 3.29
3 3.28
4 3.29
5 3.28
6 3.28
7 0
8 3.26
9 3.29
10 3.28
11 0.398
12 3.26
13 3.27
14 3.29


u8600
1 3.26
2 0
3 0
4 3.29
5 0
6 0
7 0
8 0
9 0
10 0
11 3.29
12 3.40
13 3.28
14 3.29
 

2informaticos

Administrator
Staff member
My error, 1V05_S0 requires 5V_S0 presence.

As per datasheet, U8500/600 don't have open-drain output, so pin 11 of U8500 MUST be high, when both inputs 12 & 13 are high at same time.
Post again their voltages.
 

mushr00m

Member
My error, 1V05_S0 requires 5V_S0 presence.

As per datasheet, U8500/600 don't have open-drain output, so pin 11 of U8500 MUST be high, when both inputs 12 & 13 are high at same time.
Post again their voltages.

U8500
11 0.412
12 3.28
13 3.27
U8600
11 3.29
12 3.40
13 3.29
 

2informaticos

Administrator
Staff member
You stil have a problem with U8500.
Does it get 3V at pin 14?
Interchange U8500/600 and post voltages again.

Please, stop to quote an entire post, visible few centimeters above.
 

mushr00m

Member
Replaced again and still 3.291 pin14 U8600 and 3.289 pin14 U8500.

Any other pin specific voltage are you looking

I am actually injecting 12V (2amps) directly into the PP12V_G3H to measure these rails since I am not able to do this with the boar assembled.
 

2informaticos

Administrator
Staff member
Is OK to inject 12V there.
But set the amp limit to max first.
I can't believe how many people still think that can adjust injecting current...
 

mushr00m

Member
Still same result. The max on my PSU is 3A. I had an weird behavior I assemble back in the case and it tried three times to go to the fourth light

It light up the second one and the third one and the back to the only first one. It happened twice.

Could it be the reball of my SMC?
It's the only one thing I am in doubt with
 

2informaticos

Administrator
Staff member
U8500/600 are both same 2 inputs AND gate.
If pins 12 & 13 are high, pin 11 MUST be high too.

BTW, get a better (more powerfull) lab power supply, or use original.
 

mushr00m

Member
I just assemble it back and now I am back to first sympton. It turn on and works sometimes and another times it doesn[t work and only one light. So PSU is not a problem thats what I assume since it turn on and stay stable for sometime.

My SMC is good soldered and working

PP5V_S0 appeared back when working.

After some minutes its OFF again and it trys to light up second light and it cannot it only blinks once. Really weird behavior actually I dont expect it to turn on out of nowhere. Btw it trys to turn on blinks second light and stay only on the first one.

But important to mention again I would disregard PSU, 5V_S0 line I guess its something which is causing the second light to blink and not stay stable.

Guess something PP3V3_S4 related
 
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