820 3115B Green light sometimes, ON/OFF

[JorgePayar]

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?

 

[JorgePayar]

No Title

I know you are busy...but...any help is welcome

 

[dukefawks]

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.

 

[JorgePayar]

Ok thanks a lot

 

[larossmann]

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

 

[JorgePayar]

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]

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:

 

[larossmann]

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]

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

 

[JorgePayar]

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?

 

[larossmann]

pin 1	0.578	0
pin 2	0.568	16
pin 3	0.473	3.9
pin 4	0.478	3.4
pin 5	0.684	1.3
pin 6	0.563	3.4
pin 7	0.681	0.98
pin 8	0.478	2
pin 9	0.66	0.032
pin 10	0.443	3.4
pin 11	0.444	3.4
pin 12	0.308	3.4
pin 13	0.406	3.4
pin 14	0.45	3.3
pin 15	0.682	0
pin 16	0.605	5
pin 17	0.405	12.5
pin 18	0.406	12.5
pin 19	0.419	5
pin 20	0.42	5
pin 21	0.416	0.5
pin 22	0	0
pin 23	0.406	12.5
pin 24	0.794	13.3
pin 25	0.543	16.81
pin 26	0.575	15.93
pin 27	0.573	16
pin 28	0.569	16
	diode mode red probe on ground	voltage

 

[larossmann]

Those are my measurements from a good board a long time ago.

 

[JorgePayar]

Ok thanks but if the pin 1 is OL where can I follow the white rabbit? SMC_DCIN_ISENSE??

 

[larossmann]

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.

 

[JorgePayar]

pins 27/28: 20,2 ohms
pins 17/18: 2,8 ohms

 

[larossmann]

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]

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

 

[aprendiz]

did you measure AC IN in diode mode with charger pluged??

 

[JorgePayar]

did you measure AC IN in diode mode with charger pluged??

No, without charger why?

 

[larossmann]

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.