DELL inspiron 15 ic getting hot

[String2016]

I have problem on this dell inspiron 15, the first problem is shorted 19v rail plugging in the charger the charger light goes off, already eliminated shorted by replacing two caps and mosfet which circled in yellow below photo, the other problem now is when i plugged in the charger the ic TPS51225 is getting very hot and on the bench lab hes taking 0.15amps and the ic is very hot, so i decided to replaced with TPS51225C available on scrapboard, but still the same problem that IC is very hot no.I measured the pins based on datasheet there is no voltages on PIN6 EN2 AND PIN20 EN1, there is no voltage on VIN pin12 AND VREG5 no voltage but on PIN7 PGOOD have 19.5v. anyone can help me on this please

[Techtiger]

Re: DELL inspiron 15 ic getting hot

I have problem on this dell inspiron 15, the first problem is shorted 19v rail plugging in the charger the charger light goes off, already eliminated shorted by replacing two caps and mosfet which circled in yellow below photo, the other problem now is when i plugged in the charger the ic TPS51225 is getting very hot and on the bench lab hes taking 0.15amps and the ic is very hot, so i decided to replaced with TPS51225C available on scrapboard, but still the same problem that IC is very hot no.I measured the pins based on datasheet there is no voltages on PIN6 EN2 AND PIN20 EN1, there is no voltage on VIN pin12 AND VREG5 no voltage but on PIN7 PGOOD have 19.5v. anyone can help me on this please

No Schematic for this MB, PIN7 PGOOD +19.5V to high it should be less than 3.3V try it isolate that leg

[mcplslg123]

Re: DELL inspiron 15 ic getting hot

I doubt he'is not counting the pins correctly as it's almost impossible to have 19V on Pgood pin. Download the datasheet of TPS51225 and understand the pincount and make sure you counted it correctly.

PS: It seems he has counted PIN6 as PIN1 and that way VIN will be pin7

[String2016]

Re: DELL inspiron 15 ic getting hot

yes my mistake, ive check on wrong pinout by the way i double check on the correct pinout only pin12 vin has voltage of 19v the rest VREG3=0.84V VREG5=0V AND EN1 AND EN2 0V AND PGOOD pin 7 have 0v

[piernov]

Re: DELL inspiron 15 ic getting hot

Resistance to ground on VREG3/VREG5?

[String2016]

Re: DELL inspiron 15 ic getting hot

Vreg3= 2.01k vreg5= 9.85k

[String2016]

Re: DELL inspiron 15 ic getting hot

anyone can help on this please

[mcplslg123]

Re: DELL inspiron 15 ic getting hot

Remove TPS 51225C and remeasure resistance on VREG3/5 Pins. Dont give power to mb while TPS51125C is removed, else there will be extensive damage to the mb.

[String2016]

Re: DELL inspiron 15 ic getting hot

thanks for the response mcplslg123. I removed the ic and measures resistance on VREG3 PIN3= 2.02K and on VREG5 PIN13=0 or OL

[mcplslg123]

Re: DELL inspiron 15 ic getting hot

Vreg 3 resistance seems bit low.I doubt on kbc being bad but wait for opinion from other members.

[String2016]

Re: DELL inspiron 15 ic getting hot

does someone encounter this problem need help please

[Techtiger]

Re: DELL inspiron 15 ic getting hot

remove tps solder a lead to VREG3
Put 1V to it from LAB supply then 1A at first after 3A or more something must become hot

[Techtiger]

Re: DELL inspiron 15 ic getting hot

Vreg 3 resistance seems bit low.I doubt on kbc being bad but wait for opinion from other members.

I confirm VREG3 resistance is low

[String2016]

Re: DELL inspiron 15 ic getting hot

@techtiger I removed the chip and inject 1v 2amp-3amp on VREG3 pin 3 hes taking 0.45amps but and voltage stays to 1.0v i cannot find hot component

[String2016]

Re: DELL inspiron 15 ic getting hot

@techtiger I think i found the problem , detected this mosfet HOT when injecting 1v 3am on VREG3 , It has a mark of K45BD, i dont know this kind of mosfet, see photo attached. I cannot find the same chip with K45BD on my scrapboard i found K72H3.could this be ok to replaced with this?

[mcplslg123]

Re: DELL inspiron 15 ic getting hot

It seems like Q2501 is part of RTC circuit. can you confirm that?? If it is part of RTC circuit, then you can easily get a similar component from many dell scrap mb which has schematic.(Eg Dell Cedar 13269-1 Mb)

[String2016]

Re: DELL inspiron 15 ic getting hot

yes you are right mcplslg123 i check through connectivity on positive side of RTC connected to the pin 3 of the shorted mosfet . i have only one scrapboad of dell motherboard i cannot find that has MARK K45 same as the shorted one

[mcplslg123]

Re: DELL inspiron 15 ic getting hot

Dont go after the mark. Different manufacturer uses different marking. MB code for the dell scrap mb you have?? Schematic avlvl for that board?? If so i can help you find it on the scrap mb.Look at Page 24 of dell cedar 13269-1 mb schematic. Either of those two components is your ic. Did you counted the pins correctly this time??I'm attaching a pic how to count pin correctly.

[String2016]

Re: DELL inspiron 15 ic getting hot

thanks for the response. I have only 1 dell old scrap board available with board code DAUM8AMB8D0 REV. yes i count the same as pic you attached

[mcplslg123]

Re: DELL inspiron 15 ic getting hot

Unfortunately dell mb you have dont have that part.