Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

[Jmine]

Hello guys,

I've got this motherboard with me that turns on when the charger is connected(without pressing the power button), the fan is fully spinning and it doesn't display anything. there is led flashing 3 amber 5 white. voltage readings are also weird, sorry I couldn't find the schematics for the board.

Voltages are as follows,

@ PL5301: 1.015V
@ PL4401: NO voltage
@ PL4501: 5.100V
@ PL4502: 3.408V
@ PL5101 near RTC: NO voltage
@ PL5001, PL4801 PL4802, PL4701: NO Voltages
@

Looking forward for your guidance on this.

Ihave attached an image of the board

PS: Consider me as a beginner to troubleshooting electronics

[mcplslg123]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

You can use 17831-1 schematics to troubleshoot as thats almost identical.

PL5101 is for ram voltage and should be 1.2V. With no voltage on PL5101, you cant expect Vcore/gfxcore to come up. So the focus should be on PL5101 coil.

What is the voltage on pin3-4 of PU5151/PU5401?? They are respectively for 2.5V and 1.8V.

PU5101,pin7/8/9/11/12 Voltage??

Measure resistance on all coils and post it here.

[mcplslg123]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Reference Schematic

[Jmine]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

You can use 17831-1 schematics to troubleshoot as thats almost identical.

PL5101 is for ram voltage and should be 1.2V. With no voltage on PL5101, you cant expect Vcore/gfxcore to come up. So the focus should be on PL5101 coil.

What is the voltage on pin3-4 of PU5151/PU5401?? They are respectively for 2.5V and 1.8V.

PU5101,pin7/8/9/11/12 Voltage??

Measure resistance on all coils and post it here.

Thank you for the reply

PU5151 pin3: 2.54v
pin 4: 3.3v

PU5401 pin 3: 1.8v
pin4: 3.4v

pu5101: pin7: 0v /8: 3.3v : /9: 0.75v /11: 5.1v /12: 5.1v

@ PL5301: 38k
@ PL8601: 25k
@ PL4501: 20k
@ PL4502: 4.1k
@ PL5101: 0 ohms
@ PL5001: 0.9ohms
@PL4801: 0.7ohms
@ PL4802: 0.7 ohms
@PL4701: 7.3ohms

[mcplslg123]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

PU5101, pin7 should be 3.3V, rest all pins are ok.

Are you sure about the resistance check on PL5101??
Was this resistance check with ram stick inserted??
If yes, remove the ram stick and re-measure resistance on PL5101. This coil should be above 100 Ohms atleast.

Worst thing can a shorted cpu but lets check the basics to be sure.

[Jmine]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

PU5101, pin7 should be 3.3V, rest all pins are ok.

Are you sure about the resistance check on PL5101??
Was this resistance check with ram stick inserted??
If yes, remove the ram stick and re-measure resistance on PL5101. This coil should be above 100 Ohms atleast.

Worst thing can a shorted cpu but lets check the basics to be sure.

Hey,

I checked the PL5101 in both instances and the value is 0 ohms.

I noticed that someone has already worked on the board and i think some components are missing around PU5101.I have attached an image.

PC5109 connected to 19th pin of PU5101 is Shorted to ground. when removed and checked but the cap is not shorted.

[mcplslg123]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Remove PU5101 and check resistance on PL5101 again(No power should be attached while this IC is removed). If its still 0 Ohms on PL5101, your SOC is definitely shorted.

[Jmine]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Remove PU5101 and check resistance on PL5101 again(No power should be attached while this IC is removed). If its still 0 Ohms on PL5101, your SOC is definitely shorted.

Yesterday I disconnected one pad of the PL5101 and measured both pads. I've got 26k on the pad connected to the PU5101 and the other pad is shorted to ground. I injected 1.0v to the shorted pad of the coil and it's taking some current.

[mon2]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

What is the current draw? Who is heating up?

[Jmine]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

What is the current draw? Who is heating up?

@ 1.0v 2.3-2.4Amps, I cannot feel any heat anywhere on the board. Could this be a shorted cap labeled as EC?

[mon2]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Can you confirm how you are checking the short condition?

In resistance mode, select the lowest scale -> measure the resistance to ground. Post the reading.

In diode mode, RED meter probe - yes RED to GROUND. Black meter probe to the point to measure. What is the diode mode reading ?

If you are drawing this much current, there is a shorted part somewhere - is the CPU heatsinked ?

The cap you are referencing may be the silk screen for the EC controller IC. Can you post a picture ?

Do you have IPA (alcohol - pharamacy grade is what we use) - IPA will mist away with enough heat and that will be the part that is the issue.

[Jmine]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Can you confirm how you are checking the short condition?

In resistance mode, select the lowest scale -> measure the resistance to ground. Post the reading.

In diode mode, RED meter probe - yes RED to GROUND. Black meter probe to the point to measure. What is the diode mode reading ?

If you are drawing this much current, there is a shorted part somewhere - is the CPU heatsinked ?

The cap you are referencing may be the silk screen for the EC controller IC. Can you post a picture ?

Do you have IPA (alcohol - pharamacy grade is what we use) - IPA will mist away with enough heat and that will be the part that is the issue.

Resistance to ground 0.002ohms
Diode mode 0.002v



Are these attached to 1.2v rail.? These are the EC caps I mentioned before.( Please see the attachment )

CPU is heat sinked. Removed the sink, CPU is not heating.

I will find some IPA and try to find if something heats up

[Jmine]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Do you have IPA (alcohol - pharamacy grade is what we use) - IPA will mist away with enough heat and that will be the part that is the issue.

IPA doesn't evaporate. I guess I should give up now.

[mon2]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Can your power supply support a higher current? If yes, crank it up higher but leave the voltage at 1volt.

Then check again if someone is heating up.

We use the Short Killer tool and it claims to offer upto 30A spikes. We dial it up to 0v8 and has worked well to split apart shorted caps, etc.

Perhaps you can purchase a similar tool in your local market.

[mcplslg123]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

PL5101 consumer side(the side which is connected to cpu) is shorted and its a clear indication of shorted cpu part of SOC unless someone is lucky to find a shorted cap.

[reformatt]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Given the poor rework in that area of the buck converter, 99.9% probable CPU is shorted.

Poor mans thermal camera is those rosin flux pens the Chinese are selling now.

[Jmine]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Can your power supply support a higher current? If yes, crank it up higher but leave the voltage at 1volt.

Then check again if someone is heating up.

We use the Short Killer tool and it claims to offer upto 30A spikes. We dial it up to 0v8 and has worked well to split apart shorted caps, etc.

Perhaps you can purchase a similar tool in your local market.

I've maxed out the amps to 5A and the amps start at 1.9 something and gradually goes until 2.5A.

[Jmine]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

PL5101 consumer side(the side which is connected to cpu) is shorted and its a clear indication of shorted cpu part of SOC unless someone is lucky to find a shorted cap.

Just want to clear this.

Does the CPU always heat up when it is shorted? In this case it doesn't heat up.

[mcplslg123]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Just want to clear this.

Does the CPU always heat up when it is shorted? In this case it doesn't heat up.

Theoritically yes it should heat up but keep in mind that the SOC is a large bga package and so wont heat up vigorously. It needs 1V/10A to even mildly heat up on this package.

[Jmine]

Re: Dell Vegas/Turis MLK KBL-R 17841-1 WX2RR

Theoritically yes it should heat up but keep in mind that the SOC is a large bga package and so wont heat up vigorously. It needs 1V/10A to even mildly heat up on this package.

So that's when a thermal camera comes in handy.

I just assembled the laptop and giving it back. Thank you guys very much for helping