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LENOVO B460 NO POWER ON 51123 HEAT


BOARD- 09922-1M LA46 UMA


DIGNOSIS-



CHECKED THE DC AMP IT CONSUME .300AMP (SUSPECTED SHORTING ISUUE)

CHECKED THE 3.3V/5V COIL( L8-L9) FOR SHORTING BUT DIODE MODE 390ohm ok

but L8 3.3v line heat excess and only 2.5v insted of 3.3v

L9 5V OK NO HEAT

SO I AM CONFIM IT ONLY PROBLEM WITH 3.3V LINE OF STEP DOWN

SO I AM CHECKED THE STEPDOWN IC 51123 VREG3 & VREG5 PIN 8 & 17 , HERE 3.3V, 5V OK

SO THAT CONFIRM 51123 IS ALMOST OK

SUSPECTED GO TOWARD VO2, AND LL2 PIN OF 51123, HERE ALSO 2.5V INSTED OF 3.3V

MEANS VOLTAGE DROP FOR ANY SHROT OF CAP OF LINE 2 OUTPUT

SO THAT CHECKED THE VBST2 AND IT SHOW ME SHORT WITH LL2, VO2 PIN

VBST PIN AND LL2 PIN ARE CONCTED WITH C281 CAPCITOR AND CHECKED IT FOUND SHORT

FINALLY FOUND C281 SHORT



ACTION-

REPLACE THE C281 WITH NEW ONE AND CHECKED 3.3V OK 5V OK AND NOW BOARD ON

DONE DISPLAY OK AMP CONSUPT MORE THEN 1AMP

very vey nice Case Studies .....

Good case
Help full for me
Thanks

[ Post made via Android ]

Very well explained but how to find same capacitor

SIR GOOD CASH STUDY
AND VERY USE FULL SOLUTION

One Ans I usually use a capsiter residing on every MB by CPU or any supply its polized cap I use instead of this cap
As replacement nd placement much difficult I make Sol for it a normal cap that's 330 or 220 if diff accordingly use a formula of capitance c=1/c1+1/c2........

[ Post made via Android ]

SIR SKBASIR. do you have backup bin for this model? can you please upload? i really need bin for this model. thank you so much.