LG Flatron E2742V-BN, need help identifying Voltage regulator

[Gavin Winning]

Hi people, I recently been given a out of warranty 27" LG Flatron LED monitor E2742V-BN, and it wouldn't turn on, even the power button wouldn't light on. Open it up and i found the Voltage regulator blown (i assume it is). Can't identify the part number on it as the middle is blown (not even with my handheld 60X microscope).
Would any one be able to tell or suggest an alternative component?

https://www.dropbox.com/s/i5ni3jb3j3g9klq/20170609_193624_HDR.jpg?dl=0
https://www.dropbox.com/s/whwkec3y9eon2dg/20170609_192900_HDR.jpg?dl=0

 

[73's de Edd]

Sir Gavin Winning . . . . .


¿ WHASSAMATTAHYOU ?

I had no trouble in making out the APW7302Bee. . . . particularly the AP and the 02Bee.

Check roadmap . . . .Da-Da sheet below, and use DVM in low ohms function to see if pin 2-3 or 3-4 are shorted.

The 19VDC power brick might be bad ( PLUS . . . it should be the original unit ), no question on this chip being bad, and a short might be present on its 5V power output line.

Normally 19VDC POSITIVE comes into pin 2 and 5VDC POSITIVE leaves out of this chip at its pin 3.

Da DA:

http://www.datasheetlib.com/datasheet/1360257/apw7302b_anpec-electronics.html?page=9#datasheet

73’s de Edd

 

[Gavin Winning]

Sir 73's de Edd
Thx so much for your prompt reply, feels like Santa put a gift in my X'mas stocking when i woke up!~
Now i can place an order on ebay~
Pin2 read 19.18V, Pin7 read 4.61V, all other pins read 0V.
Pin 2-3 give no beep while 3-4 beep, so 3-4 shorted, am i correct? (that whole IC gonna be replaced anyway)
19VDC power brick is the component on C149?

 

[73's de Edd]

Sir Gavin Winning . . . .

Pin2 read(s) 19.18V,
If that is true your external power block is seeming to be good and installed with proper poalarity.
Pin7 read 4.61V,
That is because that same 19VDC input voltage is being passed thru a 100K resistor and drops down to that value, as it is then connected to a voltage reference source inside that chip.
all other pins read 0V.
If all was GOOD, you also would have the units converted 5VDC supply coming out of pin 3 of that IC.

19VDC power brick is the component on C149?

Nope, that " power brick " is the techno- slang for that separate power supply that has AC line power coming into it and putting out 19VDC via its cord that connects to the monitior.
Your mentioned C149 seems to be a monolithic ceramic surface mount capacitor, with it probably being 1 ufd at >19v . . and .probably rated at 25 or 35 VDC.
You need to ohm out pin 3 to see that it is not shorted to ground by downstream power consuming circiitry.
No mere Beep-Beep test, but actual ohmmic readout.
Of ALL of my exotic Swiss and German end and side cutters, my best choice to clip off the pins of that IC still would be . . . . . . .cuticle nippers . . .they get VERY CLOSE in.
Then, you are being left with just single IC pins to unsolder, you won't damage the PCB foil pads.


https://www.aliexpress.com/item-img...9637.html?spm=2114.10010108.1000017.1.RvxIyi#


73's de Edd

 

[Gavin Winning]

Sir 73's de Edd,

I found the APW7302B on ebay but they have different code on the second line. Namely A07BS,,, A062C....A077T.... i think those are just batch number and don't really matter, right?

Need to do further reading on how to "ohm out " pin 3 ( indeed, i've never receive any professional training, just interested in fixing things and hopefully can learn something in different projects)

....so after few hours i tested the resistances across each pin and ground (the metal bracket or panel)
readings as follow
https://www.dropbox.com/s/qmvnjafij91hb8v/20170612_221430.jpg?dl=0

not sure why pin8 and pin6 give different reading when using 2M and 200K range respectively.
pin1 shows approx 1.627 when using 2K range (with a diode symbol on it).
pin2 reading wouldn't stablize, it fluctuate between approx 80 to over 200. Mostly between 110 and 128.
pin3 reads 3.8 when pin 4 read 3.1, and 3.0 when pin 4 read 2.4
(Background resistance including my probes approx 0.9)

Last time I just heat the pins and suck the solder with the solder sucker then lift the whole thing up with pins still on.
Good to keep one of this nippers in tool box tho.

 

[73's de Edd]

In looking up the pinout for you confirmation I see that I C has a bottom soldered heat sink pad.
You qualified for non destructive hot air rework ?

 

[Gavin Winning]

Yea, thats what i wanted to ask as well. I was thinking just drag flux the new ic, then stick a larger heat sink like i usually do on a computer GPU. Sounds crap.