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[help] FIRST POST: 820-00840 DEAD AND HOT AS HELL

P

phantom

Member
Hi guys i have an 820-00840 that not boot... (stuck at 5v)

here there is the history of previous techician (i can't say if it is 100% true)

macbook dead

found a short with thermal camera on c3000

caps removed (not replaced)

tried to charge -> smoke

found u3100 burnt

changed, no luck

changed u3200 no luck

rechanged u3200 with the original one. No luck

now i have this laptop.



i have changed both usb-c chip from a IDENTICAL donor board and C3000

FINALLY 20V! BUT NO BOOT

Using Thermal camera i have u7800 super hot

Scarica

Una cartella/file condivisa è disponibile per il download e lo streaming con UploadNow a questo link
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I have checked for shorts around and under u7800 with no luck



I have pp3v3 ldo 3v
I have ppbus pmic 13v
I have pp1v25_ref 1,3v

But pp5v ldo stuck at 2,7v This Line is not shorted


replaced u7800 (from donor board)

Now i have po5vldo… u7800 is not super hot anymore…(but hot together with u7100)

Now is super hot u3900 and a little bit cpu…

This is the amp meter

https://uploadnow.io/f/nJDYmsx

Changed u3900 still the same

I have Nothing on display, no caps lock no fan spinning
 
2informaticos

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

Check if the redriver chip is not also burnt.

USB-C redriver.jpg

drive.google.com drive.google.com

Do you get 3V3_S5?

Check diode mode to ground on all big coils and other test points.
Compare with good board, or reference table.

After all, CPU may be dead; be aware of that.
 
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P

phantom

Member
thank you for your reply!

redriver chip seems perfect

yes i have 3v3_s5 stable

checked big coils with this awesome table chart you gave me...seems all ok
 
2informaticos

2informaticos

Administrator
Staff member
Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L (at same time).
First, be sure SMC_ONOFF_L stays normally high at 3V.
 
2informaticos

2informaticos

Administrator
Staff member
Please, confirm if that drop pulse was on PM_PWRBTN_L.
STOP uploading videos; just reply the questions!
 
2informaticos

2informaticos

Administrator
Staff member
You should have pulse at PM_SLP_S3_L too; confirm that.
Then check for pulse at all big coils; when trigger SMC_ONOFF_L.
You can use SW9988/89 pads, instead of power button; solder R9988, if not in place.

Test if machine turns on in SMC bypass mode.
 
P

phantom

Member
PM_SLP_S3_L goes to 3,3 as soon as i connect power suppply, then come back to 0 after some seconds then to 3,3 (stable)

r9988 is not in place...should i do a jumper with a wire? is the jumper for "bypass mode"?



ps you ask me to trigger SMC_ONOFF_L

then you said that i can use sw9988..but it is SMC_ONOFF_L _R : is it the same?
 
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2informaticos

2informaticos

Administrator
Staff member
Not the same, if R9988 is not soldered.
Mentioned pads are bigger and more easy to use; but imply soldering R9988.
However, if you feel comfortable, just use an wire soldered to SMC_ONOFF.

If PM_SLP_S3_L remains high, then you should have voltage on all big coils; maybe not on CPU coils.
 
P

phantom

Member
PM_SLP_S3_L and PM_SLP_S4_L goes to 3,3 as soon as i connect power suppply, then come back to 0 after some seconds then to 3,3

but this behavious is WITHOUT trigger SMC_ONOFF_L

if i try to short SMC_ONOFF_L nothing happen!

i have no voltage on the 3 big coils on the left of the cpu

I have u3900 and ssd super hot (47 degrees), then u5800 and u7800 hot
 
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2informaticos

2informaticos

Administrator
Staff member
Power on sequence starts when charger is connected.
I said to test triggering SMC_ONOFF_L, because you didn't mention to have voltage on any big coil; apart of 3V3_S5.

L7410/20/30 will not get voltage as normal; nor even when board boots.
What voltage do you get on L7210/20, after 10s?
If nothing, check L7370 voltage too.

BTW, when you deal with groups of 2-3 coils, good enough to check one coil only.
 
P

phantom

Member
l7730 1v
l7900 1v
l7960 0,9
l8030 1,1
l8060 1v

u8200 ok
u8205 ok
u8210 ok
u8220 ok
u8260 ok
u8280 ok
u8230 ok
u8250 ok
u8240 ok
 
2informaticos

2informaticos

Administrator
Staff member
Probably CPU problem then.

Just in case, try known good BIOS.
Also check all BootROM SPI Bus Series Termination resistors and their traces.
 
P

phantom

Member
can you help me with a good bios?

Where i can find bootrom spi bus termination?

why don’t you care about hot chip?
 
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