820-3764-A, short

[Max7]

A water damaged logic board. Cleaned up and replaced quite a few parts. However, eventually hit this issue.

Upon applying power to the board, after about 1 second, R7020 gets extremely hot. There is no short to ground on either side of the resistor and each side reads 60-70K to the ground. Resistor itself is fine at 47ohm. D7005 are fine, so does C7092, 91, 90.

The part I get confused is that ping 2 of the resistor reads 16.5V, and pin 1 ready 3.3v ! Pin 1 connects to DCIN ISOL BLEEDER circuit on the upper part of page 51. What does this circuit do ? Mosfet Q7010 was warming up a bit (with no shorts), replaced it just in case but made no difference. Q7020, Q7030 are not installed, adding more to the confusion.

How can I figure out the source of the over current going through R7020 ?

Thanks

 

[2informaticos]

You didn't say anything about PPBUS_G3H and 3V42_G3H.
Start checking diode mode to ground on both; also check voltages, if exist.

Remove R7020 and post voltage on both pads.

 

[Max7]

PPBUS_G3H = 1v, Diode mode voltage drop 0v
3V42_G3H = 0.250v, Diode mode voltage drop 0.125v

After removing R7020, pad 1 = 16.5v, pad 2 = 1v
EDIT: I actually removed F7140 as well when I got the above reading, when I put it back pad 2 drops to 0v.

 

[2informaticos]

"ping 2 of the resistor reads 16.5V, and pin 1 ready 3.3v
..........................................
pad 1 = 16.5v, pad 2 = 1v"
Where is the error?
Please, post accurate information from the beginning!
You had all the time 16.5V on pad 1 (coorect in fact).

I repeated thousand times on the forum; STOP wrtiting end "V" on diode mode readings.
We don't need confusions.

"Diode mode voltage drop 0v"
No idea what this means.

One of C7090-92 has leakage, or bad U7090.
Check U7090 pin 6 voltage, removing C7090-92 one by one.
If still low, change U7090; check voltage without resolder it first.