Acer Aspire 5750-Dead, No Power or Lights

[kev4eva]

Folks am stuck here, really need your help. Got a VIN/ Power in problem

*Got 19 volts at dc jack connect PJP1 and PL1....page 46
*PQ6- got 18.5 volts on input and output........page 47
*PQ7- only 18.5 volts on pins 1-4,........ 0 volts on output

think i have a problem here, am stuck,

From here on all other components are 0 volts
PR14, PL22 PUL- measure 0 volts..................

missing 5v reg and 3 vreg as current seems to stop at PQ7 ??

Did i miss a cap or resistor possible faulty that you can point in schematic. Would appreciate any help....am beginner


schematic: Acer Aspire 5750 schematic

Motherboard Image

[whaldsz]

Re: Acer Aspire 5750-Dead, No Power or Lights

Voltages at pin 1,2, 3, 23, 24?

[kev4eva]

Re: Acer Aspire 5750-Dead, No Power or Lights

Voltages at pin 1,2, 3, 23, 24?

PU2- 5v and 3v regulator

0 volts on all those pins.....input an output....so i think the voltage is cut off somewhere before here whether at the second fet PQ7 ?

PQ7 -18.5 volts pins 1-4 then 0 volts on the others pins

[popeye]

Re: Acer Aspire 5750-Dead, No Power or Lights

Have you removed and checked PQ7 this is a p channel mosfet the gate needs to be more negative than the sorce to turn on the voltage for the battery if you have the battery in you need to check PU1 pin 24 DC inyou should have supply voltage Vin you should have you should have voltage (high) on pin 3 EN
this switches on the ic that controls the alws3v & alws5v regulators at U2

[kev4eva]

Re: Acer Aspire 5750-Dead, No Power or Lights

Have you removed and checked PQ7 this is a p channel mosfet the gate needs to be more negative than the sorce to turn on the voltage for the battery if you have the battery in you need to check PU1 pin 24 DC inyou should have supply voltage Vin you should have you should have voltage (high) on pin 3 EN
this switches on the ic that controls the alws3v & alws5v regulators at U2

havent removed PQ7 as yet, i tried with battery in at PU1 pin 24 is 0.2volts and pins3 en is 0.3 volts

PU2 doesnt switch on as no voltages there, i will remove PQ7 shortly and update you

[kev4eva]

Re: Acer Aspire 5750-Dead, No Power or Lights

PQ7 seems fauly so i just replaced it...now

Pins 1-4 =18.5 volts
Pins 5-8= 0.4 volts...... was 0 volts before, hmmm seems something draining current here..so turns out PQ7 not the issue??

[whaldsz]

Re: Acer Aspire 5750-Dead, No Power or Lights

Voltages at pin 1,2, 3, 23, 24?

Sorry, im talking about PU1.

Check the voltage at the cathode of the zener diode on pin 1 of PD5. VIN has 18.5V, so probably the PD5 or PR22 could be open.

[kev4eva]

Re: Acer Aspire 5750-Dead, No Power or Lights

Sorry, im talking about PU1.

Check the voltage at the cathode of the zener diode on pin 1 of PD5. VIN has 18.5V, so probably the PD5 or PR22 could be open.

thanks, suprisingly PD5 = 18.5 volts

trying to locate PR22....i see a resistor i think cud be it but got no labels will try magnify the area an locate it

[whaldsz]

Re: Acer Aspire 5750-Dead, No Power or Lights

If PD5 has 18.5V, and you dont have a voltage on pin 24 of U1, then PR22 could be open. PR22 is connected to one end of PD5. It should read 20 ohms according to your schematic diagram.

[kev4eva]

Re: Acer Aspire 5750-Dead, No Power or Lights

If PD5 has 18.5V, and you dont have a voltage on pin 24 of U1, then PR22 could be open. PR22 is connected to one end of PD5. It should read 20 ohms according to your schematic diagram.

thanks i really glad your helping me so far

found pr22 its connected to positive pin of PD5, its closest to it but unlabelled on pcb

PR22= reads 18.5 volts on the one end and o volts on the other

sorry for my noob question but...whats the best range to set my meter on to measure PR22 resistance..2000 ohms??

[kev4eva]

Re: Acer Aspire 5750-Dead, No Power or Lights



that should be PR22....has a light surface abrasin

PR22= pin 1=18.5v
pin2= 0v

[whaldsz]

Re: Acer Aspire 5750-Dead, No Power or Lights

that should be PR22....has a light surface abrasin

PR22= pin 1=18.5v
pin2= 0v

PR22 should read 10 ohms. Your measurement indicates it's open. Replace it.

[Francisco.s]

Re: Acer Aspire 5750-Dead, No Power or Lights

If PR22 is open, then there are many possibilities that PU1 be in shot-cicuit.

[kev4eva]

Re: Acer Aspire 5750-Dead, No Power or Lights

will do that an post in the next few hours.....any 10 ohm black smd resistor will do with value of 100??

[kev4eva]

Re: Acer Aspire 5750-Dead, No Power or Lights

i replaced PR22...it reads 10ohms, when i give power now it doesnt turn on an after reads 1.5 ohms

now: any 10 ohm resistor i replace at PR22 its destroyed

[kev4eva]

Re: Acer Aspire 5750-Dead, No Power or Lights

cud PU1 IC be faulty?-i notice dc in pin24 is shorting to ground

[whaldsz]

Re: Acer Aspire 5750-Dead, No Power or Lights

Yes, remove PU1 and test pin 24 to ground to confirm.

[spidey]

Re: Acer Aspire 5750-Dead, No Power or Lights

*PQ6- got 18.5 volts on input and output........page 47
*PQ7- only 18.5 volts on pins 1-4,........ 0 volts on output

i didnt read whole posts, but with the given information i can say that it is protection error. That means you have a short somewhere or somehow protection circuit is in error state.
i would short PQ7 pins 1 and 8, limit power supply to 3v and limit current to 200ma and connect to board. search for heat, and slowly raise voltage and current limit. it is most probably a bad cap or problem in your stand by circuit.

if you dont be careful you can damage your board.

[kev4eva]

Re: Acer Aspire 5750-Dead, No Power or Lights

*PQ6- got 18.5 volts on input and output........page 47
*PQ7- only 18.5 volts on pins 1-4,........ 0 volts on output

i didnt read whole posts, but with the given information i can say that it is protection error. That means you have a short somewhere or somehow protection circuit is in error state.
i would short PQ7 pins 1 and 8, limit power supply to 3v and limit current to 200ma and connect to board. search for heat, and slowly raise voltage and current limit. it is most probably a bad cap or problem in your stand by circuit.

if you dont be careful you can damage your board.

i wish i could do that my friend however havent purchased a dc power supply as yet am just a beginner, i appreciate your advice alot i will try retrace that circuit and also check charger IC

[whaldsz]

Re: Acer Aspire 5750-Dead, No Power or Lights

There is a very high probability that PU1 is shorted as francisco said and the result you got in post #15.