820 3115B Green light sometimes, ON/OFF

JorgePayar

Member
Hi, I have another issue with the same board, now I have green light sometimes when I plug the AC charger, sometimes not and when it turns on then turns off.
When I measure the f6905 sometimes I have 16,75V and sometimes only mV. The AC In adapter is working fine on several boards but not in this one.
The fan is spinning and it chimes, but no backlight, no image.

PPBUS_G3H is present but sometimes not, that is why I need help I don't know why this is happening.

I will explain myself better:

When I plug the charger green light: PPBUS_G3H is 16,78v for example, then I plug again the charger and I got only 1,6v on pubs_g3h

Where can I start?
 
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dukefawks

Administrator
Uhm PPBUS_G3H should never go over 12.6V! Check sense resistor circuit around U7000. R7021/22/51/52. First get this working then we will look at the video/BKL issue.
 

larossmann

Administrator
Staff member
What was the original issue on this, and where(if it was a spill)? 16v on PPBUS_G3H is f'd up!
 

JorgePayar

Member
r7021: 10,2 Ohms
r7022: 10,2 Ohms
R7051: 2,5 Ohms
R7052: 0,003 Ohms

I think they are good, can a cap be causing that?
 

JorgePayar

Member
What was the original issue on this, and where(if it was a spill)? 16v on PPBUS_G3H is f'd up!
No, ppbus_g3h is 12,5V
What is at 16V is the F6905 fuse, and was fluctuating.
Ok I have reflow U7000 and I soldered better (I think) also I replace R7052 that I thought it was bad but good in appearance.
Now green light is on most of the times when I plug the charger in. I´ve been following power lines ppbus_g3h is 12,5V good pp3v42_g3h is present too, ppdcin_g3h present but I have a question: must be d6990 fluctuating in voltage? I mean pin 1 2 and 3

it was spilt on these areas:
 

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larossmann

Administrator
Staff member
D6990 should not be fluctuating. Is PP18V5_DCIN_CONN moving up and down?

Also, when you plug the charger in, do you get 0 fan spin, or one tiny little flicker of a fan spin?

Do the caps by the T29 boost circuit look like shit?

Does U2600 area look like shit?

Does the SMC look like shit?

More hints please :)
 

JorgePayar

Member
No Title

D6990 should not be fluctuating. Is PP18V5_DCIN_CONN moving up and down?

Also, when you plug the charger in, do you get 0 fan spin, or one tiny little flicker of a fan spin?

Do the caps by the T29 boost circuit look like shit?

Does U2600 area look like shit?

Does the SMC look like shit?

More hints please :)
Ok, next episode on this mofo mobo, yesterday night everything was good, green light...
I was going to measure all the things you told me today and...no green light...now ppbus_g3h 2V hmm, then u7000 was shorting!! I quit the U7000 check pins 27 28 and they are shorted!! (diode mode = beep) still shorted without u7000

Anyway I´ll try to answer you as best as I can

D6990 should not be fluctuating. Is PP18V5_DCIN_CONN moving up and down?

PP18V15_DCIN_CONN was not fluctuating when I measured before.

Also, when you plug the charger in, do you get 0 fan spin, or one tiny little flicker of a fan spin?
0 fan spin, nothing at all

Do the caps by the T29 boost circuit look like shit?
A little bit shity, Im working on it

Does U2600 area look like shit?
Kind of... Im working on it

A little bit yes, Im gonna change caps and resistors

Does the SMC look like shit?
No, it is ok

More hints please
Sorry about the pics I don't have a camera for the trinocular port yet
 

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JorgePayar

Member
I think those pins must be like they are now, anyway I have measured u7000 pins without the chip

Values are:

pin 1:OL
pin2:OL
pin3:OL
pin4:0.563 V
pin:5:OL
pin6:0,663 V
pin7:OL
pin8:OL
pin9:OL
pin10:0.614 V
pin11:0,613 V
pin12:0,337 V
pin13:0,463 V
pin14:0,488 V
pin15:OL
pin:16:OL
pin17:0,447 V
pin18:0,447 V
pin19:OL
pin20:OL
pin21:OL
pin22: 0V (GROUND)
pin23:0,447 V
pin24:OL
pin25:OL
pin26:OL
pin27:0,903 V
pin28:0,903 V

Ok U7000 was shorted and I don't have another one right now to test it
ppbus_g3h f7040: 2V so probably T29bst is responsible as Louis said in one or their videos?
 
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larossmann

Administrator
Staff member
pin 10.5780
pin 20.56816
pin 30.4733.9
pin 40.4783.4
pin 50.6841.3
pin 60.5633.4
pin 70.6810.98
pin 80.4782
pin 90.660.032
pin 100.4433.4
pin 110.4443.4
pin 120.3083.4
pin 130.4063.4
pin 140.453.3
pin 150.6820
pin 160.6055
pin 170.40512.5
pin 180.40612.5
pin 190.4195
pin 200.425
pin 210.4160.5
pin 2200
pin 230.40612.5
pin 240.79413.3
pin 250.54316.81
pin 260.57515.93
pin 270.57316
pin 280.56916
diode mode red probe on groundvoltage
 

larossmann

Administrator
Staff member
Woah IGNORE THE FIRST PAGE DIAGRAM NUMBERS it DOES NOT correspond to actual pin numbers on the chip!

Check resistance between pins 27/28 and pins 17/18 on U7000 and post values.
 

larossmann

Administrator
Staff member
My best guess at this point is that U7000 is not soldered flatly on the board or is bad. Your measurements show no short on PPBUS_G3H
 

JorgePayar

Member
AC IN U7000 DIODE MODE 0,005 V Could be bad that u7000?
But when I measure ppbus_g3h with no u7000 in f7040 shows 1,8V- 2V
 

larossmann

Administrator
Staff member
CHGR_ACIN should have high resistance to ground and be 3.7-4v with charger plugged in. If it is showing very low reading to ground then U7000 is fucked.
 
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