Help Identify PJ742K chip

[Jeen]

Got this laptop that doesn't work and was going to try to identify and repair the issue. I'm a novice to this sort of thing.
laptop model Asus fx503V
zero response when plugging in power supply. no lights, no response when hitting power button.

I opened up the frame and looked for any burnt areas, but everything looked clean. I tried performing continuity tests starting with the largest chips first and came across the PJ742K. Continuity test failed on this particular chip. I don't know what it is or, don't laugh, if a continuity test would even work here.

The chip is in close proximity to where the power comes into the machine. The black block just above it is the power cable.
I tried googling it, but because I don't know what kind of chip this is, I don't know where to start in terms of codes. closest I got was a zener diode.

 

[Harald Kapp]

A continuity test is by no means a way to ascertain the correct operation of most ics.
I can't decipher this website, but there you go.

 

[H2814D]

Google Image Result for http://img.alicdn.com/imgextra/i1/3969414804/O1CN01Dykwq91lMHdq90MaU_!!3969414804.jpg

I was able to find a photo match for the PJ742K and messing with that page it shows up as a diode/LED. You could try removing one leg and testing it as a diode and see what happens.

 

[JP-Stereo]

This is not a "CHIP".
This is a capacitor, inductor or a resistance...
Just check if it have a reading of around 740kohm with a multimeter.
If so it's a good resistor.

 

[Jeen]

Thank you everyone for the suggestions. I'll try to get in there in the next couple of days and try out your suggestions and post my results.

I also notice that two of you linked to taobao.com. I'll poke around there a little more with the given information and see what comes up.

 

[Jeen]

Went ahead and performed the tests. resistance on that circuit was sitting about 111.5k, I am thinking it is a resistor and it's probably still working.

I also noticed my universal power supply is short about 2amps for the laptop's power requirements. It's also probably short 60watts from the 120watts requirement. The give away there was a problem is that the light on the power supply turns off when I plug it in. It could be a short, but I can't be sure until I have a "oem" replacement part to test with.

In any case, the requested circuit has been identified enough that it can be tested. I will proceed with closing this thread. Thanks for the help, everyone.

 

[Harald Kapp]

I am thinking it is a resistor

With 99.9999999 % certainty it is not. The marking is completely atypical for a resistor. It's more like a diode.

The website I linked shows no details, not even with the help of google translate. But it definitely shows the component as a diode.
To check the component you will have to remove it from the circuit and use the diode test function of your multimeter to verify the basic operation (go/nogo) of the diode.
Note: testing components in circuit requires special equipment to isolate the measurement from the influences of other components. You can't do that with a multimeter alone. That's why I suggest to remove the diode from the circuit for measurement.

The give away there was a problem is that the light on the power supply turns off when I plug it in.

Very likely the overcurrent protection is being activated, shutting down the power supply.
Always make sure to exclude external potential sources of error - as a mismatch in the power supply - before diving into the analysis of a circuit.

 

[danadak]

This guy quite effective repairing LapTops and his training videos with simple tools.

Part marking https://smd.yooneed.one/code504a.html#google_vignette

Post a pic that shows more of the board area surrounding that chip, maybe some clues
there....


Regards, Dana.

 

[Jeen]

Okay. I goofed up. I just had an underpowered power supply. The new one just came in and it powers up fine. I didn't check the power requirements as Harald Kapp had mentioned. Thanks for all the help everyone.

 

[davenn]

This is not a "CHIP".
This is a capacitor, inductor or a resistance...
Just check if it have a reading of around 740kohm with a multimeter.
If so it's a good resistor.

no it isnt

 

[davenn]

Got this laptop that doesn't work and was going to try to identify and repair the issue. I'm a novice to this sort of thing.
laptop model Asus fx503V
zero response when plugging in power supply. no lights, no response when hitting power button.

I opened up the frame and looked for any burnt areas, but everything looked clean. I tried performing continuity tests starting with the largest chips first and came across the PJ742K. Continuity test failed on this particular chip. I don't know what it is or, don't laugh, if a continuity test would even work here.

The chip is in close proximity to where the power comes into the machine. The black block just above it is the power cable.
I tried googling it, but because I don't know what kind of chip this is, I don't know where to start in terms of codes. closest I got was a zener diode.

It 99% probability of being a diode