820-01598 no power

[Kyle93]

Arrived with liquid damage primarily in U6903 area. Replaced U6903 and all affected components. When turned on PP3V3_G3H and PPBUS_G3H are fluctuating drastically including CHGR_EN_MVR. stuck at 5V on charger.

What should be checked next?

 

[TCRScircuit]

1. The rails on these machines usually cycle when there is a short somewhere. Post Resistance to GND values on PP3v3_G3H, PP3v3_G3H_RTC and PPBUS_G3H.

2. Do you have steady 5v on PPDCIN_G3H?

 

[2informaticos]

Remove F7000 and check C7050 and C6912 voltages.

 

[Kyle93]

5v is not steady on meter

Resistance to GND PP3v3_G3H 1.580 PP3v3_G3H_RTC 1.2 PPBUS_G3H 10.30 million


Fuse removed

C7050 12.36v

c6912 0v

 

[2informaticos]

"PPBUS_G3H 10.30 million"
Do you mean short to ground, when F7000 is in place?

"Fuse removed
C7050 12.36v"
Good enough, because of missing 3V3_G3H...
"c6912 0v"

Post U6903 voltages.
Use surrounding components as test points.

 

[Kyle93]

No short to ground on PPBUS_G3H .400 diode mode with fuse in place



PPVIN_G3H_P3V3G3HRTC flucuates .700V to 0V

P3V3G3HRTC_PHASE1 fluctuates from .200V to 0V

P3V3G3HRTC_PHASE2 fluctuates from .200V to 0V

P3V3G3HRTC_PGOOD fluctuares .600V to 0V

P3V3G3HRTC_FB FLUCTUATES .200v TO 0v

CHGR_EN_MVR flucuates 2.2V to 0v

 

[2informaticos]

Sorrry, I forgot this is T2 board.
PPBUS_G3H MUST appear first; is the "mother" of all voltages, including 3V3_G3H.

"Resistance to GND ... PPBUS_G3H 10.30 million " (miliohm to ground???)
----------------
No short to ground on PPBUS_G3H .400 diode mode"
Can you clarify this???

 

[Kyle93]

PPBUS_G3H also is fluctuating however it is stable at 12.36V if R6907 is removed

Yes no short on PPBUS_G3H .400 diode is correct

 

[2informaticos]

Then replace U6903.
Seems that PPBUS_G3H only drops when 3V3_G3H tries to appear.

 

[Kyle93]

It’s already been replaced once

 

[2informaticos]

Remove R6934/35 and check if PPBUS_G3H is still there.

 

[Kyle93]

Yes ppbus_g3h is present and steady with R6934/35 removed

 

[2informaticos]

C6912 voltage?

"Resistance to GND PP3v3_G3H 1.580"
What's that, ohm, Kohm?
Post diode mode (red probe at ground) on pad1/R6934.

 

[Kyle93]

C6912 11.05V

it was ohms

0.0001 diode on pad1/R6934

 

[2informaticos]

"C6912 11.05V"
More than needed to fry T2, CPU and god knows what more .
Check R6912/13 values (ohm mode).

So you have short on 3V3_G3H.
I hope you understand the need of posting correct/useful information now.

You can use voltage injection method, to find the culprit.
Take your time and read the forum, if you are not sure how to.
If is not T2/CPU, you can spend some more time with this board.
However, MUST get correct C6912 voltage, before resolder R6934/35!!!

 

[Kyle93]

When injecting voltage looks like U7800 is getting warm. Is this chip possible to replace?

Set power supply to 3V at 5amps. Put positive wire on pad 1 of R6934

 

[2informaticos]

Read more about voltage injection on the forum.
If not, you can risk to fry something in the future!

Remove U7800 and check if short gone.
If yes, replace the chip.
Not sure if have board specific firmware.
Just in case, take one from donor, same model board.

 

[Kyle93]

Can you send link on what to read for injectuing voltage in situations like this? Always thought it was as simple as injecting the power into the rail unless its PPBUS_G3H and in that case check the mosfets first.


where do you get donars for this model? I haven't had any luck finding them

 

[2informaticos]

Start injecting with 1V and increase slowly, if needed; do not exceed 4V.
Set amp limit to max on the PSU first.

Getting T2 scrap board is really dificil...