Lenovo T490s completely dead

[Andreasbest]

Hello!
I received a fantastic T490s that is completely dead, after i removed the back cover i noticed a totally fried cap (attachement) pic, i remove it and cleaned the pcb, seems undamaged, although the nearby caps are shorted, PU1001 looks physically undamaged.
Any advice please?
Thank you in advance!

Scehmatics, boardview and damage picture in attachement.

[Andreasbest]

Re: Lenovo T490s completely dead

Also find fried PR0212.
The fried cap was PC1002.
The shorted caps are PC1004 and PC1005

[reformatt]

Re: Lenovo T490s completely dead

VSYS15 pretty much goes everywhere. You need to use 1V voltage injection and thermal camera. Feeds all DRMOS IC's for the CPU/GPU so you need to be pretty careful not to exceed a volt if any of them are shorted.

PR0212 is a current sense resistor for the battery. Can't believe that is burnt up when it is rated at 1W and 10 milliohms.

[Andreasbest]

Re: Lenovo T490s completely dead

I thought about voltage injection too.
Where do you want to solder+ and where -?

[Andreasbest]

Re: Lenovo T490s completely dead

I plan to inject 1v and 1a at two pins of the burned cap.
Is this correct?
Please someone respond.

[rediii]

Re: Lenovo T490s completely dead

I plan to inject 1v and 1a at two pins of the burned cap.
Is this correct?
Please someone respond.

you can inject the voltage anywhere on the shorted rail. - on ground (screw holes do have a big ground layer for example). + side on vsys side on any cap or coil for example. inject more amps, start with 2.5 a and check if you can locate the shorted component with ipa or thermal cam. did you check the mosfets with diode measurements?

[Andreasbest]

Re: Lenovo T490s completely dead

I only checked the mosfets next to PR0212, no short with GND.
I plan to inject 1v and 1a and try with thermal camera but if you want to check some mosfets first then t will be my pleasure.

[rediii]

Re: Lenovo T490s completely dead

I only checked the mosfets next to PR0212, no short with GND.
I plan to inject 1v and 1a and try with thermal camera but if you want to check some mosfets first then t will be my pleasure.

ok, so you do have a thermal cam, that's good. go for the injection, rise the amps until you can locate the shorted area(s)

[Andreasbest]

Re: Lenovo T490s completely dead

I don't see anything heat up with 1v 1A
Should i increase or it's dangerous for CPU?

[Andreasbest]

Re: Lenovo T490s completely dead

I proceed with 1V 2A and found PC1201 shorted.
Replaced them both but i can't find replacement for PR0212.
Any suggestions?

Also now the shortcircuit is gone, should i check any mosfet or anything else or we are fine?

[rediii]

Re: Lenovo T490s completely dead

I proceed with 1V 2A and found PC1201 shorted.
Replaced them both but i can't find replacement for PR0212.
Any suggestions?

Also now the shortcircuit is gone, should i check any mosfet or anything else or we are fine?

PR0212 is bad? are you sure, measure resistance between both ends and tell us the measurement (no power/no battery). do the same with the mosfets (PQ0203, PQ0202: gate <-> source <-> drain <-> gate) nearby, but in most cases they should be fine. hopefully you fixed it

[Andreasbest]

Re: Lenovo T490s completely dead

One end 150kΩ, the other 0.8ΜΩ.

Yes PR0212 was totally fried, check attachment above.

What can i do to replace PR0212, can't find anywhere 1w 10mΩ SMD resistance.

[rediii]

Re: Lenovo T490s completely dead

One end 150kΩ, the other 0.8ΜΩ.

Yes PR0212 was totally fried, check attachment above.

What can i do to replace PR0212, can't find anywhere 1w 10mΩ SMD resistance.

if you want to do it very dodgy do a solder bridge. no spare boards with this resistor? it's the same on every laptop (near dc in or battery).

[Andreasbest]

Re: Lenovo T490s completely dead

if you want to do it very dodgy do a solder bridge. no spare boards with this resistor? it's the same on every laptop (near dc in or battery).

I have mainboards from Dell E6540, Dell E6430, Dell Precision M4800 and from Dell Precision 7510
I can't find any 1W resistor in them, can you please check on their schematics and point me?

[SMDFlea]

Re: Lenovo T490s completely dead

I have mainboards from Dell E6540, Dell E6430, Dell Precision M4800 and from Dell Precision 7510
I can't find any 1W resistor in them, can you please check on their schematics and point me?

Search for some at digikey or other electronics distributor in your country

1W 0.01 1% 1206

https://www.digikey.gr/en/products/f...FJthQDYQBdAXyA

[Andreasbest]

Re: Lenovo T490s completely dead

I already made a search for it in Greece, haven't found anything.
Order is too expensive for 1 piece, so perhaps the donor boards is the best solution.
Do you know if it's any available on these??

[Andreasbest]

Re: Lenovo T490s completely dead

Do you want to upload schematics for the above models to have a look?

[SMDFlea]

Re: Lenovo T490s completely dead

Do you want to upload schematics for the above models to have a look?

If they`re already posted in the forum just link to them. If you have one that isn`t on the forum you can bet there`s a request thread for it, post your schematic there then link to it. There aren`t that many 1206 sized parts on boards now, so search 1206. If all the schematics are compal they sometimes use the same naming convention such as 0.01_1206_1%

[Andreasbest]

Re: Lenovo T490s completely dead

Here are all the schematics of donor boards i have available, please help me found one.

So far i see:
In E6540 PR701 and PR716
In E6430 PR1326
In M4800 PR723
In 7510 PR723

LA-C541P https://www.badcaps.net/forum/showpo...44&postcount=1
LA-9771P https://www.badcaps.net/forum/showpo...51&postcount=2
LA-7782P https://www.badcaps.net/forum/showpo...68&postcount=2
LA-9411P https://www.badcaps.net/forum/showpo...39&postcount=9

What do you think?

[Andreasbest]

Re: Lenovo T490s completely dead

Bump