Macbook Air A1466 2015 no chime, no image (PP0V6_S0_DDRVTT)

Moss

New member
Hello.
The laptop turns on, but there is no chime and image.

U7400
1 - DDREG_VTTSNS - 0
2 - PP1V2_S3 - 1.2
3 - PP0V6_S0_DDRVTT — 0
4 - GND
5 - PPVTT_S3_DDR_BUF — 0
6 - DDREG_1V8_VREF - 1.8
7 - GND_DDREG_SGND
8 - DDREG_FB - 1.2
9 - DDREG_VDDQSNS — 1.2
10 - GND
11 - DDREG_DRVL - 0
12 - PP5V_S3 - 5.05
13 - DDREG_LL - 1.2
14 - DDREG_DRVH - 1.2
15 - DDREG_VBST - 6.2
16 - DDREG_EN - 3.31
17 - MEMVTT_EN - 3.31
18 - DDREG_TRIP - 0-
19 - DDREG_MODE — 0
20 - DDREG_PGOOD — 3.3 if present, do you need to worry about PP0V6_S0_DDRVTT ?

also missing
PPHV_S0SW_LCDBKLT — 0
EDP_BKLT_EN — 0
PP15V_TBT — 0

replaced U7400 and Q7430, nothing has changed!
There is no short circuit on the board!

PP1V8_S3 - 1,8
PP1V5_S0 - 1,5
PP1V2_S3 - 1,2
PP1V05_S0 - 1,05
PP1V05_SUS - 1,05
PP1V05_S0SW_HSIO - 1,05
PPVCC_S0_CPU — 1,8
All powerGoods are present!
USB lights up!

thanks
 

2informaticos

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

Any history fault available?
Do you get PM_PCH_PWROK and PM_PCH_SYS_PWROK?
Also check CPU_VCCST_PWRGD and PLT_RESET_L.
 

Moss

New member
Thx)
the motherboard is clean!
The only thing that I noticed strange is that with a 45W power supply the board starts up, and with 85W it detects but does not start, is this normal?


PM_PCH_PWROK — 3,4
PM_PCH_SYS_PWROK— 3,4
CPU_VCCST_PWRGD - 1
PLT_RESET_L — 3,3
 

Moss

New member
when the battery is connected with the adapter 85 starts. Bypassing smс also starts but without changes
and please tell me how to find VD0R sensor
Thx
 
Last edited:

2informaticos

Administrator
Staff member
"how to find VD0R sensor"
Did you search in pdf?
Look at page 42, just in case.

"how to bypass smс"
So many times explained on the forum...
Press power button, connect charger and maintain pressed 5-10s; it should start with fan spinning at max.
 

Moss

New member
Yes, I'm sorry, I found everything and did it! the message above was fixed.
Bypassing smс wish 85W also starts but without changes, no chime no image
 
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piernov

Moderator
Staff member
When you say "USB lights up!" you mean activity LED of USB drive blinks?

PPVTT_S3_DDR_BUF should be 0.6V, without it PP0V6_S0_DDRVTT will stay at 0V instead of 0.6V.
Measure exact resistance to ground on both lines and make sure C7450 and C7462 look good.
 

Moss

New member
I have a USB for tests, when I connect it, it lights up and shows that 5V is coming to it.
Everything looks fine
C7450- 2,6MOm
C7462 -0,8KOm
 

2informaticos

Administrator
Staff member
No RAM activity, if missing PP0V6_S0_DDRVTT .
Steady light on USB doesn't help.
You must test with a device which has Link LED, to confirm USB activity.

Try known good BIOS file.
 

Moss

New member
I assumed that there might be Bios, but unfortunately, they do not change the equipment for the firmware. while I'm looking for a solution with bios,
Maybe you have some other ideas that i can check?
 

Moss

New member
while waiting for the detail, I installed the BIOS from the same donor, should there be at least some changes?
it also turns on but there is no voltage 0.6v
 

Moss

New member
U7400, pins 1, 3, 5 there are no short circuits on these lines (infinity).

On all these legs, a strange value of 596.5, I don't know what it is, but it's not 0 like in other cases.
It still does not give 0.6V.
 

2informaticos

Administrator
Staff member
Impossible to get infinite (OL) reading measuring diode mode correctly!
Remeber, ALWAYS red probe at ground in diode mode.

Be aware, we not always search for pure short...
 

Moss

New member
Thanks for the tip.
1 and 3 = 0.2, 5 = 1.02
I also checked the resistance: 1 and 3 = 0.8. 5 = 2.7
 

Moss

New member
Replaced again 7400 and BIOS chip (from a new doner), no changes
maybe supply 0.6V power to this line?
 
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