Dell Inspiron 15 5575 LA-F121p

[pc1staid]

Hi everyone.
I have a small issue with the above mentioned laptop. Originally came in for a broken DC socket with the socket inner ferrel stuck in the adapter head
The adpater is not being detected, not matter which adapter I use. I have 2x45w and a 65w genuine Dell adapter and I am getting the same issue with all 3. Taken the mainboard out and found a blown diode.
Using the schematic found here https://www.badcaps.net/forum/showthread.php?t=97207 using page 46 as reference, I have taken the following measurements:-
PL3 0.7 ohms across pins 1 and 2
PR6 15.09 ohms
PR1 33.3 ohms
PR4 10.01 ohms
PR7 is a no stuff
PD2 & 3 are a no stuff
PR5 2.207 K ohms

I have done diode and resistance modes to gnd on all points inc PQ1 and PQ2 and the readings are resistance first diode second
Pin 3 PJPDC1 32.81k 0.6690v
pins 1&2 PL3 32.81k 0.6695v and 0.6671v respectively
pin 2 PD1 and pin 1 PR3 32.81k 0.6701v
Pin 2 PR3 and Pin 1 PR6 and Pin 2 PQ2 13.66k 0.Lv
Pin 1 PQ2 and Pin 2 PR4 and Pin 2 PQ1 55.16k 0.9350v
Pin 1 PR4 47.15k 0.4009v
Pin 1 PQ1 32.81k 0.6671v
Pin 3 PQ1 Pin 1 PR1 20k 0.6690v
Pin 2 PR1 and Pin 1 PR5 19.58k 0.6561v
Pin 2 PR5 17.9k 0.4051v

PS_ID at pin 16 of UE1 is 20k 0.6549v

voltages are
pin 3 PJPDC1 19.5v
PL3 19.67v pin 1 and 19.65v pin 2
Pin 2 PQ1 and pin 1 PR3 and Pin 1 PQ1 19.65v
Pin 2 PR3 and Pin 1 PR6 and Pin 2 PQ2 0.383v
Pin 2 PR6 0.001v
Pin 1 PQ2 and Pin 2 PQ1 and pin Pin 2 PR4 2.23v
Pin 1 PR4 4.99v
Pin 3 PQ1 and Pin 1 PR1 3.1v
Pin 2 PR1 and Pin 1 PR5 and Pin 16 UE1 3.1v
Pin 2 PR5 1.99v

The issue is as soon as I connect the adapter PD1 blows.
All measurments have been taken with PD1 removed.
I have removed PQ1 and PR3 thus issolating PD1 from the rest of the circuit and it has still blown. So my thinking is there is a short between Pin 3 on PJPDC1 and Pin 2 of PD1 with the idea that PD1 is where the short is. Pin 1 goes to gnd, Pin 3 is N/C. Given that PD1 is burning out would say to me that the short goes across Pin 2 to Pin 1. 7 diodes later and I am no closer to finding the short. Law of averages will show that it cant be 3 different adapters causing the same issue.

I have probably gone well overboard with the measurements but I am at a loss.
Any guidence is greatfully received.
Thanks.

[mon2]

Re: Dell Inspiron 15 5575 LA-F121p

Hi. Which diode are you placing @ PD1 that keeps blowing ? Please share the p/n & vendor or post the datasheet.

[pc1staid]

Re: Dell Inspiron 15 5575 LA-F121p

The details are from Page 46 of the above mentioned schmematic for pic 1 and I have used the ones from a LA-9431 PD1 & 2 as defined by the schematic for it page 41 in pic 2.

[Lightcap]

Re: Dell Inspiron 15 5575 LA-F121p

HI,

Did you repair this problem? I have to same.

Thank you