820-3437-B No Boot

[LCDR2]

Hi All

This is what I know.

PPBUS_G3H - 0v
PP3V42_G3H -0v

CHGR_UGATE 4mv
CHGR_LGATE - 0mv

U7100
1 -.39mv
2 18.16v
3 4.82v
4 330mv
5 0.4mv
6 0v
7 0.4mv
8 0.3mv
9 33.1mv
10 330mv
11 330mv
12 332mv
13 13.4mv
14 330mv
15 11.5mv
16 0v
17 7mv
18 7mv
19 5v
20 5v
12 0v
22 0v
23 7mv
24 7mv
25 4.77mv
26 17.65 mv
27 18v
28 18v

___

Resistance R7105 20ohms
Resistance U7100 (17/18) - 3.5 ohms
Resistance U7100 (27/28) - 20 ohms

 

[LCDR2]

Could U7090 be a problem? I went down the rabbit hole of U7100.

The hot spot is about 38 degree..

 

[2informaticos]

First post diode mode to ground at L7130 and L7095.
Also post U7090 voltages.

 

[LCDR2]

L7130 - 0.131
L7095 - 0.000

Tested Red to ground and on both sides of chip.

Does that Mean I have a short on PP3v42?

u7090
1 - 0.6V
2 - 335mv
3 - 1.6444v
4 - 0.542v
5 - -
6 - 17.52v
7 - -
8 - 17.54v
9 - -

 

[2informaticos]

For sure...

Safe to inject voltage there; start with 1V and go up if needed, no more than 4V.
Don't forget to set current limit at max on your PSU.

 

[LCDR2]

Hello

So I have removed L7095 and the short is on Pin 2 not pin 1, so does that rule out issues with U7090 ?

Just to confirm before I blow up the board...

Positive is soldered to Pin 2 of L7095
Ground is soldered to a nearby screw hole
Power Supply is set to 1v
Amps is set to max 5 (that's it's max)

... and I am looking for what gets hot using alcohol or the thermal camera?

 

[2informaticos]

Exactly.
If there is pure short, 5A PSU can enter protection even with 1V.
If this happens, try 0.7-0.8V.
In such case will be dificil to find the culprit.

Consider to get 24V/20A PSU for this purpose.

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You can go for 12V/40A even.

 

[LCDR2]

Had a quick look with thermal cam only thing that gets hot is U5000

 

[2informaticos]

Is time to change the SMC.
However, check again diode mode there, once SMC is removed; before soldering other chip.

 

[LCDR2]

I have checked Diode mode again, I get 0.337. Is it worth re-balling old SMC, or do I just go straight for a new one?

 

[2informaticos]

If short gone after removing SMC, need to change it.

 

[LCDR2]

How cross compatible are the SMC's ? Does it need to be from the exact same board number?

 

[2informaticos]

Always use SMC from donot board, to prevent any issue.

3476/3536 SMCs are interchangable, but not sure about other good equivalency.