Acer 5732Z strange power supply problem

[Maxmad]

Hello,

I faced a problem with acer aspire's 5732z motherboard KAWF0.
There is no voltage after the PQ11 (drain).

i isolated PR57 resistor as the schematic shows...
there is 18 v at pin 4 (gate) for both PQ11 and PQ10 and both mosfets have checked and are ok.

does this means a bad charger ic? (BQ24751A)? why PQ11 doesn't close?

[khaahk]

Re: Acer 5732Z strange power supply problem

PIN5 - ACDET Voltage?
PIN13 - ACGOOD Voltage?

Both PQ10 and PQ11 will open when gate turns low. That is what BQ24751A should do. At the moment there is question if it gets the adapter voltage correctly through PR69-PR70. Or it is not functioning correctly.

[rievax_60]

Re: Acer 5732Z strange power supply problem

They are P-Channel MOSFETs. A negative voltage needs to be applied to the Gate with respect to the Source to turn on.
Have you check for a short on the B+ ?

[Maxmad]

Re: Acer 5732Z strange power supply problem

Yes there is no short on the B+.
I use an external power supply to provide 19v to B+ line and voltages 3.3 and 5 are working great. PQ13 and PQ14 are also ok.


These are the voltages of BQ24751A with:

PQ11 desoldered and power adapter at VIN : PQ11 desoldered, power adapter at VIN and 19v external power to PR57:

1 ---> 0 --------------------------- 0
2 ---> 1.25 --------------------------- 19.30
3 ---> 1.18 --------------------------- 19.30
4 ---> 17.97 --------------------------- 18
5 ---> 2.67 --------------------------- 2.66
6 ---> 1.97 --------------------------- 1.43
7 ---> 0 --------------------------- 0
8 ---> 2.65 --------------------------- 2.65
9 ---> 0 --------------------------- 0
10 ---> 3.37 --------------------------- 3.38
11 ---> 3.38 --------------------------- 3.37
12 ---> 0 --------------------------- 0
13 ---> 3.08 --------------------------- 3.05
14 ---> 0.81 --------------------------- 19.30
15 ---> 0 --------------------------- 0
16 ---> 0 --------------------------- 0
17 ---> 0 --------------------------- 0.05
18 ---> 0 --------------------------- 0.04
19 ---> 0 --------------------------- 0.03
20 ---> 2.75 --------------------------- 0
21 ---> 0 --------------------------- 0
22 ---> 0 --------------------------- 0
23 ---> 0 --------------------------- 0
24 ---> 0 --------------------------- 0
25 ---> 0 --------------------------- 0.04
26 ---> 0 --------------------------- 0.03
27 ---> 0 --------------------------- 0
28 ---> 19.54 --------------------------- 19.54


Seems that there is no output... neither on pin 26 nor pin 23..

[khaahk]

Re: Acer 5732Z strange power supply problem

Pin 23 and 26 are for charging, my suggestion - change the BQ24751.

[Maxmad]

Re: Acer 5732Z strange power supply problem

thanks for your info, BQ24751 was faulty. After change voltages seems ok and now the system powers on.
However, there is no video on the screen. no boot. only fan spins for 3-4 seconds and power led, ac led are on.

All voltages rail according to schematic are ok at S1 state... (1.8 , 3 , 1.5 etc)
Tried external monitor still no video.
Bios reflashed on an external programmer after seems corrupted but still no luck.


Attached cd rom led blinks and ejects. however hard disk doesn't seem to spin. works ok on another machine.

laptop uses an intel graphics card...

do you think it needs reballing? what else can cause no boot?

[than_22]

Re: Acer 5732Z strange power supply problem

Can I have a copy of your schematic Sir,,,, pls