A820-2936-B no green light no fan spin.

[arshees]

Hi,

Need help with a A820-2936-B board. Came with no charging issue. Working fine on battery. Changed U7000 and now no green light and no fan spin. 3.3v and 5v rails missing. Where do I start..

 

[2informaticos]

Possibly bad solders on U7000 now.
Post its basic voltages: 1, 2, 3, 9, 12, 13, 14, 15, 17, 19, 20, 27.

 

[arshees]

U7000 voltages:

1 – 0.04

2 – 15.76

3 – 4.0

9 – 0.33

12 – 0.10

13 – 0.40

14 – 0.19

15 – 15.77

17 – 2.42

19 – 5.0

20 – 4.79

27 – 16.7

 

[2informaticos]

Missing 3V42_G3H; must be fixed first.

Diode mode to ground at L6995?
If good, post U6990 voltages.

 

[arshees]

L6995 short to ground. Removed L6995 and PIN 1 - 0.615 and PIN 2 - 0.005 (Short) in diode mode with red to ground.

 

[2informaticos]

Use voltage injection method, to find the culprit.

 

[arshees]

Injected 3.42v but it’s drawing only .14 amps and nothing heating up. Am I going wrong somewhere?

 

[2informaticos]

Set PSU amp limit to max first.
You can inject 4V without problems.

 

[arshees]

Tried with 4v but same issue. Max current drawn was .44 amps. U4650 was mildly heating up. Removed it but shorting still persists.

 

[2informaticos]

Then resistance to ground have been increased.
Check it now; there shouldn't be short anymore.

 

[arshees]

0.617 on PIN 1 and 0.033 on PIN 2.

 

[2informaticos]

0.033 is still bad.
But high enough to make injecting voltage useless.

Check the capacitors connected to 3V42_G3H power rail.
Pay atention to ones connected near audio codec.
There must be one under plastic foam, near BIL connecter; it fails many times.

 

[arshees]

Checked all capacitors near the audio codes. Nothing suspicious. I am a newbie and would appreciate if you can give me part numbers to check on the 3V42_G3H power rail.

 

[2informaticos]

Click 3V42_G3H in boardview and check all caps you find there.
On this board is no cap placed near the BIL connector, my error.

There are very sensitive IR cameras on the market.
Can help you to detect very small temperature differences.
You should inspect all components connected to 3V42_G3h power rail.