820-00165 green/orange light sometimes. no fan spin

OK I'm half way through, it's a ton of work. basically all of the lines are pulsing. both in and out volatges. they're not present but they are pulsing when connected. But two things which are strange.


1. PP1v05_S0 only has 200 ohms somestimes less to ground, in fact in continuity mode my multimeter beeps.

1. and this one is completely bizarre to me. U8050 and the line SMC_PWR_EN is 0V when power is going to the macbook. as soon as I disconnect it goes to 3V. WTF? it takes at least 30 seconds for the 3 volts to disappear even though there's no power going to the board
 
Checked all of them, apart from the strange issues mentioned above, I have found no other problems. I do wonder what's different about U8020 though
 

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"PP3v3_S3_FET_R is down on every other mosfet and only pulsing except for U8020"
PP3V3_S3_FET_R is not related with U8020.
Do you get stable 3V3_SUS?

"U8050 and the line SMC_PWR_EN is 0V when power is going to the macbook. as soon as I disconnect it goes to 3V"
Do you mean SMC_SENSOR_PWR_EN?
Check SMC_PBUS_VSENSE level.
Remove Q5050 and see if SMC_SENSOR_PWR_EN changes its reaction.
 
Sorry yes I meant 3v3_sus is down on everyone except u8020
and yes SMC_PWR_EN whoops

SMC_PBUS_VSENSE is down

Hmm I can't find Q5050 on the board view
 

2informaticos

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Yeah, Q5500.
SMC_SENSOR_PWR_EN is controlled by SMC.
When power is disconnected, SMC cannot pull it down and some remanent voltage on the board will keep it high.

Did you try BIOS?
 

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You can try with a chip from donor, IF you know is good for sure.
If not, reflash the chip; don't forget to make backup first.
 

2informaticos

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Mmmhh, I don't think, if the board tries to start at least.
But this cannot assure 100% good SMC.
Did you check if VCORE pulses too?
Also check for voltage pulse at all L/C blocks close to PCH, near PCH corner...
 

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So you can detect pulses on all coils, less the CPU ones?
Post exact resistance to ground, in ohm scale this time.
Compare with values from known good working board; with same type of CPU (i.e. i5, or i7)
 
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