820-3115 no power

[Kyle93]

Arrived with minor liquid damage on U7941 Q7335 Q7330 Q2815 and Q2800. Replaced everything but still have 15V onPPBUS_G3H. Fan spins a couple seconds then stops then continues e.t.c

Replaced Q7030 Q7035 and U7000 at the same time but still 15V on PPBUS_G3H

What should be tried next?

 

[2informaticos]

Probably bad R/C7025 and Q7030 burnt again...

 

[Kyle93]

Changed R/C7025 U7000 Q7030/Q7035 at the same time. Still 15V PPBUS_G3H

 

[2informaticos]

R7020 beeps with L7030?
If yes, Q7030 is shorted...

 

[Kyle93]

No beep between R7020 and L7030

 

[2informaticos]

Post again L7030 and R7020 voltage.
Did you solder correct Q7030?

 

[Kyle93]

L7030 15.70v

R7020 18.15V

yes used correct Q7030. Pulled from same model number donar

 

[2informaticos]

Change multimeter battery and measure again.

 

[Kyle93]

Meter batteries changed. Same readings.

 

[2informaticos]

Remove F7040 and post again above voltages.

 

[Kyle93]

F7040 removed

L7030 15.70V

R7020 18.15V

 

[2informaticos]

Really strange.
Post again all basic voltages for U7000; pins 1, 2, 3, 5, 6, 9, 12, 13, 14, 15, 17, 19, 20, 27.
Keep F7040 removed.

 

[Kyle93]

u7000

Pin (1) 0.014V (2) 18.17V (3) 4.3V pin (5) 2.9v (6) 3.4v (9) 0.028v (12) 3.4v (13) 3.4v (14) 3.4v (15) 0.045v (17) 1.6v (19) 5v (20) 5v (27) 18v

 

[2informaticos]

Now you have 1.6V at L7030???

 

[Kyle93]

Readings go from 15.70V at times to 4.45V at other times on L7030 even though there is a constant 1.6v on pin 17???

 

[2informaticos]

Check R7050/51/52 and their traces.

 

[Kyle93]

they all check out good and traces are good

 

[2informaticos]

Pin 17 is directly connected to L7030.
At least should be, through 0+0.01 ohm=10 miliohm in total.
How can you get different DC voltage reading then???

BTW, measure ALWAYS DC voltage on the output pin of a coil from a buck-converter.