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[SOLVED]Old 820-2530 Charger Green then Orange No Power

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rany

rany

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Hi,
We have two 820-2530 not powering up - no fan spin at any moment, exhibiting:
Green then orange light on charger, then we try to jump start by shorting pin 5 to ground, and the orange light disappears for a few seconds, only green remains. Then orange comes back.
Anyone can help with any clues?
And is there a shortcut to testing if SMC is bad?
TIA!
 
larossmann

larossmann

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Staff member
What voltage is PPBUS_G3H? 12.23v or 12.56? Latter is good SMC, former is usually bad?

What's the resistance between pins 17/18 & 27/28 of U7000?

How does U5000/U5001 area look?

When you short SMC_ONOFF_L to ground, does PM_PWRBTN_L move? This is a two person measurement job unless you're an octopus.

Will this turn on from a charged battery without magsafe?
 
rany

rany

New member
What voltage is PPBUS_G3H? 12.23v or 12.56? Latter is good SMC, former is usually bad? 12.27V

What's the resistance between pins 17/18 & 27/28 of U7000? 20.5 Ohm and 20.5 Ohm

How does U5000/U5001 area look? Clean, no pry damage, nothings seems burnt, no evidence of liquid damage on the board anywhere.

When you short SMC_ONOFF_L to ground, does PM_PWRBTN_L move? This is a two person measurement job unless you're an octopus.
On U5001 SMC_ONOFF_L measures 3.42V, when I short it to ground, PM_PWRBTN_L as measured on TP451 decreases from 0.021V to 0.018V.
P.S.: I soldered a long battery wire to U5001, stuck a probe in TP451 via, stuck another one in a ground hole (I have extremely fine probes), and touched the long jumper to ground while looking at the DMM screen.

Will this turn on from a charged battery without magsafe? No.

After connecting the (original 60W) charger today to take the requested measurements, I observed that now green and orange lights are gone on the board I'm working with. I did not perform any repair yesterday. All voltages are present at U6900 and U6901. All I did yesterday was to remove and re-solder a resistor near ISL, resistance measurements on ISL, and some voltage readings.
Only peculiar thing with this board is a 0 Ohm resistor connecting the ground pads of the capacitors on CHGR_VDDP and CHGR_LGATE, that seems to have been added as an after-thought but in the factory. This is the one I removed then put back.

Oh and at some point today SMC was getting warm. Not hot.
 
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larossmann

larossmann

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Staff member
12.23v on PPBUS_G3H rather than 12.56v means the SMC is not communicating with U7000. If the data line between the two is intact, meaning not shorted to ground, then 99% SMC is bad or is not being told to turn on properly. What do you get on SMC_RESET_L? SMC_RESET_L has to be 3.4v for the SMC to turn on and work, but should take a short period of time to rise after PP3V42_G3H stabilizes.
 
rany

rany

New member
When you asked about U5000 I checked voltages and SMC_RESET_L was 0.15V on Pin 1 of U5000. Measured more than once.
I am assuming data line from U7000 to SMC is SMC_AC_OK? If yes, not shorted, voltage drop is 0.497.
Also green light on charger sometimes comes back.
 
larossmann

larossmann

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anything between 0.431-0.499 is normal for the SMC data line. the issue here is that the SMC will not start until SMC_RESET_L is 3.42v.

So either

1) R5000 is bad/doesn't have PP3V3_S5_SMC on pin 1
2) U5000 is bad
3) SMC is bad and pulling down SMC_RESET_L
4) Q5032 is shorting SMC_RESET_L to ground because SMC_TPAD_RST is present on pin 5
5) Q5032 is bad and sending SMC_RESET_L to ground.

My guess is 2 or 3. You said SMC gets warm, so....
 
rany

rany

New member
Ok I did replace R5000 and got green and oranges lights back. Still no fan spin.
I tried swapping the SMC and still no change. I am not sure the donor was any good and I don't stock such an old model. Been trying to find another replacement. Will update ASAP.
Thanks for everything till now. Helped me understand the SMC reset circuit for next time, instead of PLZBROing it.
 
rany

rany

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PPBUS = 12.56V @ F7000
PP3V3_S5_REG = 3.319V @ L7220
3V42 = 0.330 red on ground from Pin 5 of U6901
 
rany

rany

New member
Can you tell me "why" 5.2 K is too low? Can something else be pulling it down that I need to rule out first next time I see this?
 
D

dukefawks

Administrator
Could be something else, but from experience it is always the MCP. Anything on the 3V42 bus could be causing it, but in most cases I found it to be the MCP. Normal resistance is over 20K.
 
rany

rany

New member
Thank you.
Before testing for resistance, I have to make sure SMC is working properly or this is separate?
Could I have from the beginning tested this rail for resistance and not bothered with fixing the SMC?
 
rany

rany

New member
Just as a last update. Those guys had sent me a donor board together with the board that needed fixing.
i ended up fixing the donor board so to was somewhat a success.
 
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