820-3437-B water damage, green light, no fan spin

[Sr. Robot]

Hi, got an 820-3437-B with corrosion on C7115, C7116 and R7116. Replaced them and also replaced U7100 just in case.

Trace from C7115 to R7116 was blown and soldered jumper. Both C7116 were also blown, soldered one side to probe point near R7116 and another jumper across the board to pin 1 of Q7155. Continuity from all pins of U7100 seems to be ok, however, board is destroyed under under C7116 from the corrosion.

Now the board shows green light and then orange. No fan spin.

PPBUS_G3H is 1.3v, no signs of heat generation. Diode mode on PPBUS_G3H is 0.116

 

[2informaticos]

Post U7100 basic voltages; pins 1, 2, 3, 9, 12, 13, 14, 15, 17, 19, 20, 27.
Check resistance between pins 17/18 and 27/28.

Also post diode mode reading at F7140 in reverse way (black probe on ground).

 

[Sr. Robot]

Pin1: 0v
Pin2: 14.7 v
Pin3: 3.92 v
Pin9: 3.394v
Pin12: 3.394v
Pin13: 3.357
Pin14: 3.359v
Pin15: 0v
Pin17: 1.339
Pin19: 5.04v
Pin20: 5.04v
Pin27: 0v

Resistance pins 17/18: 3.6 ohms
Resistance pins 27/28: 20.01 ohms

reverse Diode mode F7140: 0.0

 

[2informaticos]

"Pin9: 3.394v
-----
Pin27: 0v
--------
Resistance pins 27/28: 20.01 ohms"
Check these again.
Pin 28 voltage?

Did you measure resistance directly between pins 27/28???

 

[Sr. Robot]

Sorry:

Pin 9: 0
Pin 27: 14.55
Pin 28: 14.4v
Resistance pins 27/28: 19.8 ohms
Yes, direct resistance

 

[2informaticos]

"reverse Diode mode F7140: 0.0"
Do you mean OL maybe; you've posted no short before.
PLEASE, post accurate information.

 

[Sr. Robot]

Yes, OL

 

[2informaticos]

Then you have more damage caused by corrosion around U7100.
Check all the traces, solders and adjacent components.

 

[Sr. Robot]

I double checked, all solder joints are ok. There's continuity from every single pin of U7100. All resistors around have correct values.

The trace that goes from C7102 to C7105 was corroded and blown but still had continuity. I made a jumper from C7105 to C7102 but still same PPBUS_G3H value.

 

[2informaticos]

Change the capacitors; some of them may be damaged by corrosion.