Lenovo 700-15ISK-80RU - Standby voltage missing

[EdwardGeo]

Lenovo 700-15ISK-80RU - Standby voltage missing

In Short: the laptop was flooded with water 3-4 years ago, but after service cleaning was working fine, except battery wont charge on it. After years, a month ago, laptop just shutdown itself and never power on.

After first board review, the short circuit was found. The capacitor died and burned pad. The temperature was so high that the two layers of textolite were burned. Good news that the layers was GND, so nothing critical. The burned fragment was cleaned and the short gone. Replaced them, but no standby voltage. When plugin DC, the 3.3v and 5v comes on but on one second and then off. the 19.9v are onboard.

Adding schematic, boardview, scanview at zips

[mcplslg123]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

Its normal for 5VALW and 3VALW to appear for a second and off 'coz of DEEP SLEEP WELL(DSW) feature on newer boards. Notice your dc supply consumption- it may start with 10-20mA and drop to 01-03mA once it goes to deep sleep. When you trigger, it will first come up from deep sleep stage to S5(that's when you will once again get voltage on 3/5V ALW coils) and then moves up the power sequence. So your problem may be elsewhere.

[EdwardGeo]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

Its normal for 5VALW and 3VALW to appear for a second and off 'coz of DEEP SLEEP WELL(DSW) feature on newer boards. Notice your dc supply consumption- it may start with 10-20mA and drop to 01-03mA once it goes to deep sleep. When you trigger, it will first come up from deep sleep stage to S5(that's when you will once again get voltage on 3/5V ALW coils) and then moves up the power sequence. So your problem may be elsewhere.

Thanks for replying!
I done force applying 5v on usb/hdd line and the board becomes really hot in the location of up4501 (can't remember the label). That ic responsible for generation main voltages: 3.3v, 5v.

Almost forgot: the power button reacting on power on, but only on one second. So I think the best way to replace that IC and power controller, as it looking like after hard times.

The main question: why so many capacitors were died... because of corrosion or high pulsating on pwm controller?

[mcplslg123]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

Check if PCH is alive or not after removing 3/5V pwm controller. Its not safe to inject 5v there as it has SOC architecture.

[EdwardGeo]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

Check if PCH is alive or not after removing 3/5V pwm controller. Its not safe to inject 5v there as it has SOC architecture.

I've done replaced dead mossfets and pwm, but they died after few seconds of power on. So get to the beginning.

Also found more new dead mossfets. The 5v again is grounded...it could be a lot more defective components that I have imagined...


Need to desolder all capacitors.

[FrozenHaxor]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

Need to desolder all capacitors.

No need at all. Remove the 5V coil and inject a maximum of 3,3V on the load side, check for what's getting hot and investigate.

[EdwardGeo]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

No need at all. Remove the 5V coil and inject a maximum of 3,3V on the load side, check for what's getting hot and investigate.

Found some few dead capacitors, but that is not solved 5v.

The last who could possibly use 5v is pch or Embedded controller?


Will test with 3.3 with limit of 100 mah.



Also I saw that gpu oscillator is cracked.



The other could be possibly dead is cpu. mosfets on 20v to 1.2v has resistance of 40 ohms, but shouldn't have it. But maybe need to look at datasheet of them

[FrozenHaxor]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

Will test with 3.3 with limit of 100 mah.

That's not nearly enough. Limit the current to 5A. Point of 3.3V is to avoid overvolting another rail in case there is an internal component short that has two rails in contact. I've seen it happen. Sometimes even starting with 1.5V is a good idea if you're uncertain and the board is badly damaged.

You'll never heat the short with just 0.1A enough to detect it, most of it is being lost in power supply leads anyway unless you use thick copper wiring.

Found some few dead capacitors

Define dead, were they shorted out? Which capacitors were they? Please post a picture. That's very unusual to have more than 1 damaged capacitor on those boards.

[EdwardGeo]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

That's not nearly enough. Limit the current to 5A. Point of 3.3V is to avoid overvolting another rail in case there is an internal component short that has two rails in contact. I've seen it happen. Sometimes even starting with 1.5V is a good idea if you're uncertain and the board is badly damaged.

You'll never heat the short with just 0.1A enough to detect it, most of it is being lost in power supply leads anyway unless you use thick copper wiring.


Define dead, were they shorted out? Which capacitors were they? Please post a picture. That's very unusual to have more than 1 damaged capacitor on those boards.

Added images. The first HiQ scan at first post.

Red - mean dead.


The story of board is sad: it was flooded with wine, after few years was extremely overheat (the isolation plastic is heat deformed) and the last is short and burn of layers

[FrozenHaxor]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

Is the carbonized laminate section scorched down to deeper PCB layers? Dig that black stuff a bit, it could be a multi layer short, doesn't look good. I've sometimes had to grind out mosfets that were completely welded in.

[EdwardGeo]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

Is the carbonized laminate section scorched down to deeper PCB layers? Dig that black stuff a bit, it could be a multi layer short, doesn't look good. I've sometimes had to grind out mosfets that were completely welded in.

Yeah, three layers. But seems that they were gnd

[EdwardGeo]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

after I have removed all capacitors, Embedded controller, two pwm from 5v, the resistance to ground fall to 50 ohms. All those components were dead. After I add 1.2 v to 5v line with safe overload up to 4.5a, the resistance to ground start dropping to 19 ohms and power supply was automatically poweroff with overload at more than 4.7A.

The last one mossfets who are connected to 5v is cpu power rails. If they are dead, then we know the reason. Continue desolder tomorrow. That's very interesting case.
If solder new capacitor at 5v it will die immediately.

Also ordered replacement motherboard replacement.

[EdwardGeo]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

I think that the reason of that problem is partially dead mossfet that converts 19v to 5v, so 20v jump to those components. But how 35v capacitors died is the question

[mcplslg123]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

I'll never suggest to inject more then 1V/5A on any rail if mb has SOC to avoid damage to cpu+pch. Injecting 3v or 5v on a shorted rail may kill pch/cpu if you have any leaky/shorted high side mosfet on cpu/gpu area. Sometimes its very difficult to find out what is heating with only 1V/5A injected and that's why i boght another dc supply with 10A capability. It heps when i inject 1V/10A on the shorted rail.

[FrozenHaxor]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

I'll never suggest to inject more then 1V/5A on any rail if mb has SOC to avoid damage to cpu+pch. Injecting 3v or 5v on a shorted rail may kill pch/cpu if you have any leaky/shorted high side mosfet on cpu/gpu area. Sometimes its very difficult to find out what is heating with only 1V/5A injected and that's why i boght another dc supply with 10A capability. It heps when i inject 1V/10A on the shorted rail.

Yep, that's a very good advice. Also thick cables help quite a bit, otherwise all the current gets lost on the way to the board.

I think this board is a complete loss looking at this laminate, especially with layer to layer shorts. Once the FR-4 gets carbonized, the laminate gets permanently conductive in that spot and only gets a lower resistance with time.

[EdwardGeo]

Re: Lenovo 700-15ISK-80RU - Standby voltage missing

Finally solve a short on 5v.
Now I have 150 ohm resistance to ground and power usage of 75-150 mah. The phase now is stable and even with 5v. I waited for 15 minutes and everything is okay.

So need to find out why those pwm, ldo and capacitors died. If their pins have no short, then that motherboard have a chance to be repaired