820-2610-A Sys onewire help, no green light. Please help from the gurus

[lcdcaps1]

Hi

I have an 820-2610-A motherboard that has no green light.
I have noticed is when I do a SMC reset the light on the Magsafe blinks.
From My understanding, the sys onewire circuit is responsible for the green light on the magsafe
The sys onewire circuit on this model and others is more involved
I was hoping if anyone knows about this and how it works, can reply and let me know
I know this is an old model but I am sure there are people who still works on these or knows about them

I get 1.1v on the C7771 capacitor and will replace this when I get a green light but, My first priority is to get a green light

I have been doing some voltage checks
I get the 16V rail and the 8.4V rail.
When it comes to the sys onewire rail I get nothing.
I will really appreciate it very much
Thanks all

[mon2]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

Are you using a known good REAL 85W charger?

You have the power on chime? Display working?

https://boards.rossmanngroup.com/thr...-turn-on.3703/

[lcdcaps1]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

Thanks for the reply
Yes using a genuine charger

No green light on magsafe
no display

I am sure something is wrong with the sys onewire circuit but need some help who knows the circuit well
As it is an old circuit not many people know about it or work on them
but i am hoping someone that knows the circuit can reply and help me
please
Thanks

[reformatt]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

This is an older circuit compared to later models but the principles are still the same.

SYS_ONEWIRE is a bidirectional bus between the charger and the SMC. So regardless of the intermediate circuitry, the SMC needs to have PP3V42_G3H as valid, SMC_RESET_L from U5000 is high. You can always have a dead SMC on occasion.

SMC_AC_BCOK (=CHGR_ACOK) from U7000 also needs to be high. This will allow PP18V5_DCIN_CONN to pass via Q6910. This in turn powers the overvoltage detection op amp and enable FET Q6915. This in turn switches on dual FET Q6920 to pass your SYS_ONEWIRE data bus to the charger.

In addition, 15" machines need 85W chargers. SMC determines via SYS_ONEWIRE the charger that is connected, and won't assert PM_BATLOW_L if it's underrated. So you won't get PM_SLP_S4_L going high.

[lcdcaps1]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

This is an older circuit compared to later models but the principles are still the same.

SYS_ONEWIRE is a bidirectional bus between the charger and the SMC. So regardless of the intermediate circuitry, the SMC needs to have PP3V42_G3H as valid, SMC_RESET_L from U5000 is high. You can always have a dead SMC on occasion.

SMC_AC_BCOK (=CHGR_ACOK) from U7000 also needs to be high. This will allow PP18V5_DCIN_CONN to pass via Q6910. This in turn powers the overvoltage detection op amp and enable FET Q6915. This in turn switches on dual FET Q6920 to pass your SYS_ONEWIRE data bus to the charger.

In addition, 15" machines need 85W chargers. SMC determines via SYS_ONEWIRE the charger that is connected, and won't assert PM_BATLOW_L if it's underrated. So you won't get PM_SLP_S4_L going high.

Thanks for the reply
Do you still work on these old circuits, please

I know the SMC is working because when i try and do smc reset the magsafe blinks

[reformatt]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

Thanks for the reply

I know the SMC is working because when i try and do smc reset the magsafe blinks

Correlation does not imply causation. Make proper measurements and report what each are based on the circuit description I gave you.

And I don't work on these older machines anymore. Unless an owner has a particular emotional attachment to it, no one wants to spend any money on them. In addition, they only run very old versions of MAC OS and no longer supported by Apple or anyone else. Google for example no longer updates their Chrome browsers on High Sierra anymore so most customers are complaining about web pages not displaying correctly. You either run Core Legacy Patcher, Linux or Chrome OS Flex.

The other issue with putting in time on these very old machines is that the likelihood of them bouncing on you is pretty high. A white 2009 macbook I did last year came back 3 times in a 6 month period, each with different faults. Customers always try to wrangle it as a warranty job. Just not worth the effort.

[lcdcaps1]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

Thanks for your reply
This machine is close to me that is why i want to get it going
I know that it has life in it and it is only the one wire circuit that is not working
I just did some measurements now

I jumped the power on pads and got

adapter sense 0v
smc reset l 3.4v

[reformatt]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

Sys_onewire=?
Smc_bc_acok=?
Pp18v5_dcin_onewire=?
Onewire_en=?

[lcdcaps1]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

Sys_onewire=?
Smc_bc_acok=?
Pp18v5_dcin_onewire=?
Onewire_en=?

I will be getting these measurements shortly

[lcdcaps1]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

Hi
Below are the voltages i have got so far
My CHGR_ACOK voltage seems low
If someone can verify this. I will appreciate it very much
Thanks
PPBUS_G3H 08.39v
PPBUS_CPU_IMVP_ISNS 08.39v
PPDCIN_G3H 16.63v
PP3V42_G3H 03.40v
PP5V_S3 0v
PP5V_S0 0v
F7040 08.38V
F6905 16.63V
D6900, PIN 1 0V
U6915 PIN 1 08.29V
U6915 PIN 2 GND
U6915 PIN 3 0V
U6915 PIN 4 08.15V
U6915 PIN 5 16.62V
Q6920, PIN 1 source 0V
Q6920, PIN 2 gate 0v
Q6920, PIN 3 drain 0v
Q6920, PIN 4 source 0v
Q6920, PIN 5 gate 0v
Q6920, PIN 6 drain 3.4v
CHGR_ACIN 3.9V
PPDCIN_G3H 16.62V
CHGR_ACOK 3.2V
L6995 PIN 2 3.4V

[lcdcaps1]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

Here are some more measurements
PPBUS_G3H 08.39v
PPBUS_CPU_IMVP_ISNS 08.39v
PPDCIN_G3H 16.63v
PP3V42_G3H 03.40v
PP5V_S3 0v
PP5V_S0 0v
F7040 08.38V
F6905 16.63V
D6900, PIN 1 0V
U6915 PIN 1 08.29V
U6915 PIN 2 GND
U6915 PIN 3 0V
U6915 PIN 4 08.15V
U6915 PIN 5 16.62V
Q6920, PIN 1 source 0V
Q6920, PIN 2 gate 0v
Q6920, PIN 3 drain 0v
Q6920, PIN 4 source 0v
Q6920, PIN 5 gate 0v
Q6920, PIN 6 drain 3.4v
CHGR_ACIN 3.9V
PPDCIN_G3H 16.62V
CHGR_ACOK 3.2V
L6995 PIN 2 3.4V
pin 1 D6905 16.46v
pin 2 D6905 08.39v
pin 3 D6905 16.16v
Pin 1 L6995 3.413v
Pin 2 L6995 3.409v
pin 1 J6900 16.63v
Pin 2 J6900 16.63v
pin 2 of Q6910 gate 6.68v

Q6910 pin 1 and pin 2 ressistance 467.3k ohms
Q6915 pin 1 0v
Q6915 pin 2 3.2v
Q6915 pin 3 0v
Q6915 pin 4 0v
Q6915 pin 5 8.15v
Q6915 pin 6 0v


From My reading and looking at my measurements
The transistors are not working
I read that U6915 screws up and kills the transistors and should replace everything in one go
how can i be sure U6915 is good or not
thanks

[lcdcaps1]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

Hi

[piernov]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

U6915 not doing its job as a comparator, should pull pin 4 low when voltage on pin 3 is lower than voltage on pin 1.

[lcdcaps1]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

U6915 not doing its job as a comparator, should pull pin 4 low when voltage on pin 3 is lower than voltage on pin 1.

Thanks for the reply piernov
Really appreciate it very much
Do I replace U6915 as well as the transistors
The reason I am asking this is because I read that one blows the other and this keeps on happening
Thanks again

[reformatt]

Re: 820-2610-A Sys onewire help, no green light. Please help from the gurus

U6915 is open collector. I can't see how it would destroy Q6915. It's supposed to remove the bias from Q6915 by turning on when ONEWIRE_ESD is less than ONEWIRE_DCIN_DIV.
When Q6915 is off, then Q6920 is turned on for SYS_ONE_WIRE.

Would seem U6915 is faulty.