820-3437-B bad DC-IN board??

pinotschio

New member
[FONT=arial, helvetica, sans-serif]Hi, this is my first repair attempt on a 820-3437-B. The measurement on the G3H Fuse is 8.17V which is too low I guess. So I'm thinking that the DC-IN board might be bad. Weird thing is, that the LED on the charger gave green and orange light, as well as a fan spin some times when I reseated the flex-cable. So the connection seams very fragile there.. What else could it be?[/FONT]
 

2informaticos

Administrator
Staff member
You must get the correct voltage on PPNUS line (aprox 8.5V) even without LIO flex connected.
Only 5pins DC cable is sufficient to start the board.
 

pinotschio

New member
[FONT=arial, helvetica, sans-serif]So I`m getting 12,8V on Pin 2 at D7005 where I should be getting 18,5V and on Pin 3 for PPBUS_G3H I'm getting 8,17V where I´suppose to get 8,6V...Bildschirmfoto 2018-09-24 um 10.44.16.png[/FONT]
 

2informaticos

Administrator
Staff member
"So I`m getting 12,8V on Pin 2 at D7005 where I should be getting 18,5V"
You make some wrong assumption...
You don't get 18.5V from 45-60W charger.
And also forget about R7005, which drops a bit the voltage.
Even Q7010 and D7005 itself are between charger and U7090 input; where you get 12.8V.

Post some voltages on U7100; 12, 13, 9, 15.
Also check voltage and resistance to ground (diode mode) on SCL/SDA pins from J6950.
 

pinotschio

New member
Ok, so on U7100 on Pin 12: 3.36V | Pin 13: 3.36V | Pin 9: 3.36V | Pin 15: 07,06mV?? Regarding J9650 : Pin 5 +6 have shortage
 

2informaticos

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"Pin 9: 3.36V"
Muy mal, SMC thinks about overcurrent through R7020.
So check R7021/22 and traces to U 7100 ;27/28 should give 020.


"Pin 5 +6 have shortage
---
Sorry ment Pin 5 + 4"
STOP to measure in diode mode a powered board...
 

2informaticos

Administrator
Staff member
Check again pin9 of U7100.
It can't have 3V if there is 20 ohms between pins 27/28!!!

"No shorts on J6950"
I didn't ask to check for short.
Please pay atention to the requests...
 

pinotschio

New member
I'm sorry if this gets annoying for you. I checked Pin 9 again(in Voltage Mode) and it gave me: 31mV. Ok I read out J6950 and here are the measurements: Voltage mode=VM | Resistance to Ground= RG (Diodemode without MagSafe plugged in) --> Pin 5: 3,36V (VM) / OL(RG) Pin 4: 3,36V (VM) | OL (RG) . Both Pins have very High Resistance to Ground when measured in resistance mode as well. Hope I did everything right this time. I'm a complete newby.
 

2informaticos

Administrator
Staff member
SCL/SDA should indicate something on diode mode.
Check these lines with red probe at ground in diode mode.
You must get less than 1% difference.

"I checked Pin 9 again(in Voltage Mode) and it gave me: 31mV"
So, when can we trust you?
Our help is based on your measurments...
 

2informaticos

Administrator
Staff member
Please do not attach such a big pictures.
Is sufficient to post name/value for the signal...

Do you get 3V3_SUS and 3V3_S5 voltage?
Disconnect LIO board, keep only 5pins DC cable connected between MLB and LIO board.
You don't need to connect the flex until get the board turning on first.

BTW, do NOT move that flex again, when the board is powered up...
 

pinotschio

New member
The Flexcable is off since you told me to. I measured 1,8mV on R16101 for PP3V3_SUS and for PP3V3_S5 I got 1,9mV on R8133
 

pinotschio

New member
So I looked further over the board and found a ripped off pad with a may ripped off resitor (R5100). The board view and the actual parts are a bit confusing. If there is/was a resistor, any idea if this is cause of my issue and where can I jumper the pad to? Attached are some small pictures
Bildschirmfoto 2018-09-24 um 21.13.07.pngIMG_6690.JPG
 
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