Help a newbie with his first project

**jacobtc** · 04-21-2018, 07:50 AM

So, I recently acquired a Alienware 15 R1 (LA-B753P) as the guy told me it was completely dead, and I saw it as a fun project.

I have done every ordinary thing, such as resetting CMOS and leaving the RTC battery out for a while. It is completely dead, no light, nothing. The powersupply outputs 19.5V and the DC plug measures fine. I have inspected the board, and nothing seems to be obviously damaged, no burn marks, and no apparent water damage. The next step is to check for shorts, however, how would I go about doing that? I don't have a bench powersupply, so it is difficult for me to inject voltage and check with alcohol evaporation etc.

Anyone willing to give a bit of guidance?

**caspian** · 04-21-2018, 08:13 AM

is there any other voltages on the mainboard?

**jacobtc** · 04-21-2018, 09:32 AM

Quote:

Originally Posted by caspian

is there any other voltages on the mainboard?

What do you mean? Plugged in to the DC adaptor?

**caspian** · 04-21-2018, 11:45 AM

measure voltage on big coils and capacitors to see whether there are any voltages on the board other than the 19v.

**jacobtc** · 04-21-2018, 11:52 AM

Quote:

Originally Posted by caspian

measure voltage on big coils and capacitors to see whether there are any voltages on the board other than the 19v.

Will do that later! Just got back from work... Thank you so much! Really hope I can get this working!

**jacobtc** · 04-26-2018, 07:40 AM

So just got done meassuring some coils and caps. Where I have not written anything is due to also being 0V.

https://i.imgur.com/40dINwh.jpg

Also, nothing felt varm to the touch.

UPDATE: I did not feel around the lower right corner, that gets really hot, around the two medium sized coils...

**jacobtc** · 04-26-2018, 10:00 AM

These get hot:
https://i.imgur.com/ao3Unj3.jpg

PL102
PL101
PC107
PC108

**dspok** · 04-27-2018, 02:15 AM

check resistance to ground on those coils. it looks like those coils are for ALW voltages, not sure though because I can't find schematics.

**jacobtc** · 04-27-2018, 02:30 AM

Also, on the back, the IC called PU100, is getting burning hot, I can't keep my finger on it...

**jacobtc** · 04-27-2018, 02:40 AM

Quote:

Originally Posted by dspok

check resistance to ground on those coils. it looks like those coils are for ALW voltages, not sure though because I can't find schematics.

PL102 resistance to ground is 0.5 kOhm and increasing constantly, PL101 resistance to ground is 2.8 kOhm and increasing. I guess they are getting more resistant, due to getting colder over time? If I plug in power, they go down to 5ohm on PL102 and around 96ohm on PL101 when they become slightly warm.

This is the IC on the back that gets way to hot to touch: https://i.imgur.com/hJbHhtS.jpg

**jacobtc** · 04-27-2018, 01:37 PM

Anyone?

**caspian** · 04-27-2018, 01:40 PM

Now, you should read what is marked on top of the IC to identify it.

**jacobtc** · 04-27-2018, 02:00 PM

Quote:

Originally Posted by caspian

Now, you should read what is marked on top of the IC to identify it.

The IC has the following written on it: 3h=2b q2b

Now, I've searched for the PU100 IC, and another forum says that it is a TPS51285BRUKR...

**caspian** · 04-27-2018, 02:18 PM

it does not seem to be TPS51285BRUKR. or maybe it is. I do not know. I hope someone help identify it.

**jacobtc** · 04-27-2018, 02:23 PM

Quote:

Originally Posted by caspian

it does not seem to be TPS51285BRUKR. or maybe it is. I do not know. I hope someone help identify it.

This guy identified it as TPS51285BRUKR

https://ascnb1.ru/forma1/viewtopic.php?f=31&t=130165

**vinceroger69** · 04-27-2018, 02:44 PM

Quote:

Originally Posted by jacobtc

This guy identified it as TPS51285BRUKR

https://ascnb1.ru/forma1/viewtopic.php?f=31&t=130165

data sheet

**jacobtc** · 04-27-2018, 03:17 PM

Quote:

Originally Posted by vinceroger69

data sheet

The package looks different to what is in the data sheet, this one has five pins on four sides, the one on the data sheet has only pins on two sides.

**Johndill** · 04-27-2018, 08:41 PM

Quote:

Originally Posted by jacobtc

The IC has the following written on it: 3h=2b q2b

Now, I've searched for the PU100 IC, and another forum says that it is a TPS51285BRUKR...

Is this the correct schematics for your board?

PU100 page 60.

**JaroTech** · 04-27-2018, 11:51 PM

Hi, the code '3H =' comes from Richtek, the chip is a RT6585B, it is compatible with the chip TPS51285B.

**jacobtc** · 04-28-2018, 02:51 AM

Quote:

Originally Posted by Johndill

Is this the correct schematics for your board?

PU100 page 60.

Looks like it, thanks!

04-21-2018, 07:50 AM	#1
jacobtc Senior Member Join Date: Apr 2016 City & State: Aalborg My Country: Denmark I'm a: Knowledge Seeker Posts: 104	Help a newbie with his first project So, I recently acquired a Alienware 15 R1 (LA-B753P) as the guy told me it was completely dead, and I saw it as a fun project. I have done every ordinary thing, such as resetting CMOS and leaving the RTC battery out for a while. It is completely dead, no light, nothing. The powersupply outputs 19.5V and the DC plug measures fine. I have inspected the board, and nothing seems to be obviously damaged, no burn marks, and no apparent water damage. The next step is to check for shorts, however, how would I go about doing that? I don't have a bench powersupply, so it is difficult for me to inject voltage and check with alcohol evaporation etc. Anyone willing to give a bit of guidance?

04-21-2018, 08:13 AM	#2
caspian Badcaps Veteran Join Date: Oct 2015 City & State: Mainboard My Country: Laptop I'm a: Hobbyist Tech Posts: 1,478	Re: Help a newbie with his first project is there any other voltages on the mainboard?

04-21-2018, 11:45 AM	#4
caspian Badcaps Veteran Join Date: Oct 2015 City & State: Mainboard My Country: Laptop I'm a: Hobbyist Tech Posts: 1,478	Re: Help a newbie with his first project measure voltage on big coils and capacitors to see whether there are any voltages on the board other than the 19v.

04-26-2018, 07:40 AM	#6
jacobtc Senior Member Join Date: Apr 2016 City & State: Aalborg My Country: Denmark I'm a: Knowledge Seeker Posts: 104	Re: Help a newbie with his first project So just got done meassuring some coils and caps. Where I have not written anything is due to also being 0V. https://i.imgur.com/40dINwh.jpg Also, nothing felt varm to the touch. UPDATE: I did not feel around the lower right corner, that gets really hot, around the two medium sized coils... Last edited by jacobtc; 04-26-2018 at 08:50 AM..

04-26-2018, 10:00 AM	#7
jacobtc Senior Member Join Date: Apr 2016 City & State: Aalborg My Country: Denmark I'm a: Knowledge Seeker Posts: 104	Re: Help a newbie with his first project These get hot: https://i.imgur.com/ao3Unj3.jpg PL102 PL101 PC107 PC108

04-27-2018, 02:15 AM	#8
dspok Badcaps Veteran Join Date: Jan 2014 City & State: Sudurpaschim My Country: Nepal Line Voltage: 220V I'm a: Knowledge Seeker Posts: 498	Re: Help a newbie with his first project check resistance to ground on those coils. it looks like those coils are for ALW voltages, not sure though because I can't find schematics.

04-27-2018, 02:30 AM	#9
jacobtc Senior Member Join Date: Apr 2016 City & State: Aalborg My Country: Denmark I'm a: Knowledge Seeker Posts: 104	Re: Help a newbie with his first project Also, on the back, the IC called PU100, is getting burning hot, I can't keep my finger on it...

04-27-2018, 01:37 PM	#11
jacobtc Senior Member Join Date: Apr 2016 City & State: Aalborg My Country: Denmark I'm a: Knowledge Seeker Posts: 104	Re: Help a newbie with his first project Anyone?

04-27-2018, 01:40 PM	#12
caspian Badcaps Veteran Join Date: Oct 2015 City & State: Mainboard My Country: Laptop I'm a: Hobbyist Tech Posts: 1,478	Re: Help a newbie with his first project Now, you should read what is marked on top of the IC to identify it.

04-27-2018, 02:18 PM	#14
caspian Badcaps Veteran Join Date: Oct 2015 City & State: Mainboard My Country: Laptop I'm a: Hobbyist Tech Posts: 1,478	Re: Help a newbie with his first project it does not seem to be TPS51285BRUKR. or maybe it is. I do not know. I hope someone help identify it. Last edited by caspian; 04-27-2018 at 02:19 PM..

04-27-2018, 11:51 PM	#19
JaroTech Badcaps Veteran Join Date: Mar 2015 City & State: Montréal, QC My Country: Canada I'm a: Professional Tech Posts: 270	Re: Help a newbie with his first project Hi, the code '3H =' comes from Richtek, the chip is a RT6585B, it is compatible with the chip TPS51285B.