A1708 820-00840-A no power

[Roshon]

I have a A1708 820-00840-A with no power.

It puls 20V from ampmeter but 0A (only board on desk).

PPBUS_G3H = 0V and seams to be shorted. It has 0.002 on diode reading and 0.4 ohm in resistance to ground.

R7020 = 20V

F7000 = 0V and 0.002 on diode reading. After lifting F7000, PPBUS_G3H remained shorted.

F8400 = 0V and seams to be ok (it has continuity). When removed F8400, the short remainded in PPBUS_G3H,
Diode readings:

L7670 = 0.430
L7690 = 0.330
L8410 = 0.733
L7030 = 0.346
L7730 = 0.125
L7430 = 3.8
L7410 = 3.9
L7420 = 3.9
L7210 = 0.002
L7220 = 0.002
L7370 = 0.004
L8060 = 0.039
L7900 = 0.025
L7960 = 0.030
L8030 = 0.136

 

[2informaticos]

Check resistance (ohm scale) between PPBUS_G3H and L7210/20.

 

[Roshon]

9.6
9.6

 

[2informaticos]

Now post ohm resistance to ground at PPBUS_G3H (not diode mode).

 

[Roshon]

0.8

 

[2informaticos]

Then is safe to inject voltage there.
1V should be good enough to find the culprit.

 

[Roshon]

THANKS IT WAS C6482