Help me find the shorted component - Lenovo 3000 N200

[IamPritesh]

Model : Lenovo 3000 N200
Board Name : IEL10 LA-3451P


Symptoms : On pressing power button, Power LED glows for 10 seconds and shuts off. Fan does not spin. CPU is not heating at all. PCH is not hot either.

Observation - PL11- Upon pressing the power button goes to 1.05 volt and within 10 seconds is back to 0volt . PL11 has a resistance of 10Ω

I have tried injecting 1volt to see if I can find the shorted component getting warm..but no luck yet. I have also flashed the bios but nothing works.


Any suggestion is highly appreciated.

[piernov]

Re: Help me find the shorted component - Lenovo 3000 N200

Check voltage on all the large inductors after pressing power button.

[IamPritesh]

Re: Help me find the shorted component - Lenovo 3000 N200

Will check and report back.I do have 3 and 5 volt working fine though..

[KvnTM]

Re: Help me find the shorted component - Lenovo 3000 N200

Do you get +CPU_CORE on PL15 while it is on for 10 seconds ?

Check SYSON on PR266 and SUSP# on PR179. Both should be high while the board is on.
SYSON enables channel 1 on PU7 which puts out +1.8VP on PL10
SUSP# enables channel 2 on PU7 which puts out +1.05VSP on PL11

If SYSON and SUSP# go low after the said 10 seconds +1.8VP and +1.05VSP will subsequently turn off.

If so your problem isn't on the +1.05VSP rail with PL11.

Also if a power rail reaches its nominal voltage there most likely isn't a short on it.

[IamPritesh]

Re: Help me find the shorted component - Lenovo 3000 N200

I have NO +CPU_CORE . On further investigation i see that there is No PGOOD (SPOK) voltage on PU6 ( Pin2)

WHat can cause this ?

[IamPritesh]

Re: Help me find the shorted component - Lenovo 3000 N200

PU6 has no DL3 or Dh3

[IamPritesh]

Re: Help me find the shorted component - Lenovo 3000 N200

There are my measurements for the step down IC ( PU6)

[mcplslg123]

Re: Help me find the shorted component - Lenovo 3000 N200

Pin26 measurement?? Pin27 at 0.35v is wrong-should be 3.3v.Pin2(powergood) is missing- can be 3v or 5v but not sure. Have you replaced processor??It often fails on these old lenovo's. Since the laptop is quite old- a mild reflow of the whole mobo may also work. Rest of the pin measurement seems fine to me.

[KvnTM]

Re: Help me find the shorted component - Lenovo 3000 N200

A dead processor is most likely not the case here.
His whole main 3.3V rail is missing so the laptop has no chance to start.
And please do not attempt to reflow the whole board. This could create even more serious problems on big BGAs if you don't have a proper rework station.

Back to the topic...
Pin 24 & 26 are important. Those are the gate drivers for the fets.
The circuit can't work without those and they have to be connected.

Please measure Pin 4 on PQ20 & PQ30.

Pin 27 can't be 3.3v if the converter isn't working properly. Same goes for PGOOD. It will stay low if the converter isn't working.

[on/off]

Re: Help me find the shorted component - Lenovo 3000 N200

I have NO +CPU_CORE . On further investigation i see that there is No PGOOD (SPOK) voltage on PU6 ( Pin2)

WHat can cause this ?

Did you have voltage on +VSBP?

[IamPritesh]

Re: Help me find the shorted component - Lenovo 3000 N200

A dead processor is most likely not the case here.
His whole main 3.3V rail is missing so the laptop has no chance to start.
And please do not attempt to reflow the whole board. This could create even more serious problems on big BGAs if you don't have a proper rework station.

Back to the topic...
Pin 24 & 26 are important. Those are the gate drivers for the fets.
The circuit can't work without those and they have to be connected.

Please measure Pin 4 on PQ20 & PQ30.

Pin 27 can't be 3.3v if the converter isn't working properly. Same goes for PGOOD. It will stay low if the converter isn't working.

Pin 4 on PQ30 and PQ20 has no voltage and is not short either. I do have 3.3 volt on PL8 which is probably coming from Pin22 (OUT3). But there is not PGOOD ( Pin2)
Is there a way I can put some kind of jumper to SPOK signal to activate +VSBP

Did you have voltage on +VSBP?

No Voltage on +VSBP , I think we need SPOK for it to start ?

[IamPritesh]

Re: Help me find the shorted component - Lenovo 3000 N200

Pin26 measurement?? Pin27 at 0.35v is wrong-should be 3.3v.Pin2(powergood) is missing- can be 3v or 5v but not sure. Have you replaced processor??It often fails on these old lenovo's. Since the laptop is quite old- a mild reflow of the whole mobo may also work. Rest of the pin measurement seems fine to me.

I dont have a compatible processor for this one to test. Can we put a jumper to artificially generate PGOOD signal?

[KvnTM]

Re: Help me find the shorted component - Lenovo 3000 N200

I dont have a compatible processor for this one to test. Can we put a jumper to artificially generate PGOOD signal?

It makes no sense to pull PGOOD high since your +3VALWP and +5VALWP is missing if PU6 doesn't work.

Is MAX8743_B+ present on your board? Can be measured on PR76, PR77, PQ21 (Pin 5..8), PQ20 (Pin 5..8).
Also measure for VL on PR75 & MAINPWON on PR322.

+VSB derives from +B and is driven by SPOK on PQ7.
+VSB can't be present if PU6 isn't working since SPOK derives from PGOOD of PU6.

The root of your problem is on PU6.

EDIT: If you do have 3.3v on PL8 take a look at PL7 if you have 5V. Both rails have to be on to generate PGOOD.

Sidenote:
The processor isn't the cause of this issue. As the names suggest +3VALWP & +5VALWP are always on even if the board is turned off.

[IamPritesh]

Re: Help me find the shorted component - Lenovo 3000 N200

It makes no sense to pull PGOOD high since your +3VALWP and +5VALWP is missing if PU6 doesn't work.

Is MAX8743_B+ present on your board? Can be measured on PR76, PR77, PQ21 ( Pin 5..8), PQ20 (Pin 5..9).

Also measure for VL on PR75 & MAINPWON on PR322.

3VALWP is present. +5VALWP is also present. On 5volt side everything is fine. On the 3 volt side , we have 3 volt on the coil which is coming through PIN22 of PU6 and thus it shows 3.3 volt on the +3VALWP . Thus thought about jumper...
VL is present 5volt
MAINPWON is present 3 volt

[mcplslg123]

Re: Help me find the shorted component - Lenovo 3000 N200

I've thoroughly read your readings on pu6 and i know you have +3ALWP & +5vALWP. Pin27 worries me at 0.35V-should be 3v and only after that Powergood will rise. @kvntm said you have +3V rail missing which i'm not convinced at all. Since both 3/5V ALWP rails are present, i suggested a mild reflow of whole mb. I've never damaged a mb doing reflow and I never reflow bga chips unless sure. have seen hundreds of such old boards revived with mild reflow as they develeop cold/broken solder joints after such a long usage. that's my experience but one can always differ in opinion and i respect that.

[IamPritesh]

Re: Help me find the shorted component - Lenovo 3000 N200

I've thoroughly read your readings on pu6 and i know you have +3ALWP & +5vALWP. Pin27 worries me at 0.35V-should be 3v and only after that Powergood will rise. @kvntm said you have +3V rail missing which i'm not convinced at all. Since both 3/5V ALWP rails are present, i suggested a mild reflow of whole mb. I've never damaged a mb doing reflow and I never reflow bga chips unless sure. have seen hundreds of such old boards revived with mild reflow as they develeop cold/broken solder joints after such a long usage. that's my experience but one can always differ in opinion and i respect that.

I did a mild reflow for about 60 seconds primarily on the 3/5volt section and around I/O chip. Nothing has changed. I really appreciate your willingness to help others. You have helped me in the past as well.

[KvnTM]

Re: Help me find the shorted component - Lenovo 3000 N200

3VALWP is present. +5VALWP is also present. On 5volt side everything is fine. On the 3 volt side , we have 3 volt on the coil which is coming through PIN22 of PU6 and thus it shows 3.3 volt on the +3VALWP . Thus thought about jumper...
VL is present 5volt
MAINPWON is present 3 volt

If both rails are present (which I didn't knew ) then there has to be 3.3v on Pin 27. It is directly connected to the coil. Are you measuring directly on the chip? If so I'd suggest to reflow PU6 with lots of flux until it is floating on the solder. You could also give it a veeeeery light nudge. This allows the solder to move a little and connect again if there's a broken connection. The chip will snap back into place by surface tension of the solder.

There has to be a bad connection on Pin 27 it makes no sense otherwise. Everything else is absolutely fine!

I've thoroughly read your readings on pu6 and i know you have +3ALWP & +5vALWP. Pin27 worries me at 0.35V-should be 3v and only after that Powergood will rise. @kvntm said you have +3V rail missing which i'm not convinced at all. Since both 3/5V ALWP rails are present, i suggested a mild reflow of whole mb. I've never damaged a mb doing reflow and I never reflow bga chips unless sure. have seen hundreds of such old boards revived with mild reflow as they develeop cold/broken solder joints after such a long usage. that's my experience but one can always differ in opinion and i respect that.

Seems like to be the case here. Pin 27 has to be 3.3v if the rails are fine. Pin 27 is directly connected to the coil without any component in between. I didn't knew both rails were fine maybe I missed something in some reply.

[mcplslg123]

Re: Help me find the shorted component - Lenovo 3000 N200

@kvntm, yes i agree. Pin 27 at 0.35V is a puzzle to me as you have rightly said it is directly connected to the +3V ALWP coil. However, @pritesh is saying there is no changes after mild reflow of PU6. thats a bit wierd. I really dont have anything else to suggest as PU6 reading seems to be correct to me except PIN27 and Pgood pin.

[KvnTM]

Re: Help me find the shorted component - Lenovo 3000 N200

@kvntm, yes i agree. Pin 27 at 0.35V is a puzzle to me as you have rightly said it is directly connected to the +3V ALWP coil. However, @pritesh is saying there is no changes after mild reflow of PU6. thats a bit wierd. I really dont have anything else to suggest as PU6 reading seems to be correct to me except PIN27 and Pgood pin.

Completely redoing that chip could do the trick. Maybe there is corrosion on that pin under the chip. Who knows. It‘s not a bga so removing and resoldering it is no big deal.