DA0U92MB6D0 REV:D NO POWER

[NConstantinou]

Dear all,

i have the above board and on PQ21(M3016D) i have input but no output. Therefore i have no input on PR7.
i do not have similar transistor to substitute. how can i overcome this!
Thanks

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground on pin #3 = PR7 = main power rail. What is the exact resistance? If it is too low, there is a fault on the main power rail.

Connect the power adapter. Measure the voltage to ground on the gate pin # 1 on PQ21. Checking the gate voltage for this mosfet which should be higher than the voltage being passed between source / drain pins to fully enable. Gate pin should be ~25v to enable.

If not, confirm the voltage to ground of REGN pin # 16 which should be ~6v.

[NConstantinou]

The resistance of PR7 to ground is 45 OHMS. Pin 1 of PQ21 has 19v. the gate of PQ21 has 0v.
i do not get any voltage on REGN pin # 16. i replace the ic with BQ25A from another USED board board but i do not know if it is good.
is anything i can do to test the ic!
By checking the coils i found that the 3.3v coil has also 45 Ohms resistance
Thanks

[mon2]

PR7 to ground is 45 OHMS

Yes, something is wrong with the main power rail.

With no power to the board, measure the resistance from PR7 to the 3v3 coil where you measured 45R ohms to ground. What is the resistance?

[NConstantinou]

The resistance I measured was on PR7 45 ohms
Before I have changed pq34 which was short and then I focus on ic charger as my first step.

at this moment I went back to check pa34 again and I found it short again.
I changed it and now the resistance on PR7 is .5 which is normal, but 0v on PR7 which means problem with charger ic.

[mon2]

What is the resistance to ground of PR7?

[NConstantinou]

Thr resistance on PR7 now is 43K

[NConstantinou]

Doing more testing i found on PU 2 ic pin #4 is connected with 2 100k resistors. Those where having wrong value and i change them.
After that i got PR7 19V but not 3.3 and 5v.
time for that step now

[NConstantinou]

PU12. I do have +VIN 19v, pin #3 ref 2v, pin 17 VREG5 1.5v, pin 8 VREG3 0.09v, pin 13 EN0 2.5v.
what is the order of power sequence of G5608Dr51U 9PU12) ic!

IF +5VPCU WHICH IS MISSING FROM IC COMES FROM PQ7!
ON PQ7 PIN 1 AND 3 I GET 1.5V AND ON PIN 2 12V

Thanks

[NConstantinou]

I managed to get 19v rail working.
No 3/5v rail.
PL5 coil which is battery coil i get only 1.1v without battery connected.
i cheched PQ15 which is the high side on Drain i have 19v but on G i have 1.2v. it should be higher.
measuring the resistance of mosfet i found the following

S-D 57k
S-G 90K
D-G 0.27M

i substituted BQ28 with BQ25

please someone advice

[mon2]

Replace this mosfet. The resistance values are too low.

[NConstantinou]

what the values suppost to be

[mon2]

On a good mosfet, hundreds of k ohms or higher.

[NConstantinou]

ok thanks.
changing the mosfet i got 2.85v on PL5. is that normal!