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820-00165 Power issues and boot loop

Jay

Jay

Member
This machine came in as "no power", history unknown.
Connected to the PSU it drew a charge, fan would spin and CPU got warm. No POST or boot.
Took it apart and found corrosion on C0890 and C089, small spot. Cleaned it up and found one of the caps shorted to ground.
Replaced both caps and unit sat there dead. No PP3V3_SUS which I traced back to U8020 which sits right underneath the caps that were shorted. Replaced U8020.
At this point the MacBook was back to it's original behavior... fan spins, warm CPU, no POST etc.
Did an SMC reset and it fired right up! Showing the login screen.

Great! I shut it down to put the Wi-Fi card in and booted it holding "d" key for a hardware test.
back to original problem :mad:

Thought the battery looked a bit off, turns out to be a 3rd party, so grabbed an OEM KG battery to put in. Now unit draws no more than 0.800 amps and power cycles.
tested this with two KG batteries, same bahavior. Just as I'm about to give up for the day I put the 3rd party battery back in. It went back to drawing a full charge and now it power cycles and plays half of the boot chime on a loop.

Da hell... Before I spend tomorrow chasing my tail on this thing, any suggestions on where to look/what to look for? Apart from the small spot of corrosion the board was clean.

Appreciate any help :)
 
2informaticos

2informaticos

Administrator
Staff member
Press power button, connect charger and maintan button pressed 5-10s.
You can use SMC_ONOFF_L pads (R5115/16) instead .
 
Jay

Jay

Member
SMC bypass started blasting the fans at max speed. SMC reset calms it down but still original behavior.
Tossed it in the cleaner, now fans ramp up and max out when it's powered on, top case no longer responds (power button and can't do SMC reset anymore).
CPU gets very hot very fast.
 
2informaticos

2informaticos

Administrator
Staff member
Do you have sweep option on your UC machine?
If not, can damage the boards...

On SMC bypass is normal to get max fan speed.
Did you check for image, or other activity at that moment?

Do you get all voltages now?
No need to do SMC reset, if you disconnect charger and battery; is the same thing...
Check how SMC_ONOFF_L reacts using power button.
If nothing, then use R5115/16 pads instead.

Check for corroded/broken traces on the board.
UC could knocked off some components, check that.
 
Jay

Jay

Member
Yeah the UC has sweeping frequencies (one of the larger ones I got from Rossmann).
Will keep checking on this tomorrow, appreciate the help so far!
 
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