Almost dead Lenovo V15-ADA 82C7

[vpower]

Hi, I have this laptop that acts strange. If I try powering on, the power led, the numeric keypad light and the fans will turn on but the screen has no image. The fuse F2 near the lcd connector is blown, I tried to replace it with some similar fuses (1A) but it keeps blowing. I tested these mosfets with multimeter:
PQ201 drain 20v source 20v, gate 26v
PQ202 drain 20v source 20v, gate 26v
PQ5907 drain 20v, source and gate 0v (both shorted to ground too)
PQ5908 drain 0v shorted, source 0v shorted and gate 0v (connected to pin 33 of PU5901)
a lot of capacitors behind the cpu are shorted. thermal cam shows heat on the cpu shield
maybe the problem is in the backlight circuit? too bad I cannot find schemathics for this laptop.
any hint?
Boardview: https://www.badcaps.net/forum/showth...57#post1211357
Schematic: https://www.badcaps.net/forum/showth...08#post1242808

[Stevedb]

Re: Almost dead Lenovo V15-ADA 82C7

First i would give resistance to ground on all coils put it and the current sensor on the picture. So that somebody can look at it and help you how to further investigate. My gues it will be 3,3 v is shorted or and mosfet on vcore maybe.

[vpower]

Re: Almost dead Lenovo V15-ADA 82C7

sorry I'm trying to learn. with coil you mean, for example, PL401 and PL402?if yes, with multimeter in resistance mode:
PL401 open circuit on both sides
PL402 open circuit on both sides
PL5903 8,4 ohm on both sides
PR201 open circuit on both sides

[Stevedb]

Re: Almost dead Lenovo V15-ADA 82C7

So no short on the currentsensor to ground . Did you check the first second mosfet for internal short. If the are good i would look into the charger circuit the acdrive pin is the one that controls the mosfets.

[vpower]

Re: Almost dead Lenovo V15-ADA 82C7

multimeter in diode mode
no short on PQ202 (I only find short for a few seconds between source and drain after I check between gate and drain..is it normal behaviour?)
no short on PQ201
source (1 2 3) is shorted to ground in PQ5907..is this mosfet is connected to F2 fuse that keeps blowing?
I found other coils and mosfets under the cpu shield:
resistance mode
PL5901 and PL5902 around 80 ohm to gnd both sides
PQ5901 to PQ5906 I can check if it's needed.
acdrive pin... where can I find it?

[Stevedb]

Re: Almost dead Lenovo V15-ADA 82C7

I can not open boardview . Fuse blows so you must have a short can you give close up picture from the area. Fuse can only blow if you have a short.

[mcplslg123]

Re: Almost dead Lenovo V15-ADA 82C7

No point probing the charging circuit here. Measure resistance on both pads of blown fuse after removing the fuse. One side is definitely shorted. Then you need to inject voltage on the shorted side of fuse. Voltage should'nt be more then 1V.

Resistance measurements should be done twice
01.With edp cable inserted
02.Without edp cable.

No power should be attached to the board while checking resistance.

[onepic]

Re: Almost dead Lenovo V15-ADA 82C7

Hi vpower

did you manage to fix it? I run into same problem. V15-ADA 82C7 laptop power on (but no numeric keyboard light into my case) and no picture on screen or HDMI out. My one do not have soldered memory so i cand remove the 8GB DIMM from slot. If i power it without DIMM inserted there ar no beep error sound.

[luckyleo]

Re: Almost dead Lenovo V15-ADA 82C7

Hi vpower

did you manage to fix it? I run into same problem. V15-ADA 82C7 laptop power on (but no numeric keyboard light into my case) and no picture on screen or HDMI out. My one do not have soldered memory so i cand remove the 8GB DIMM from slot. If i power it without DIMM inserted there ar no beep error sound.

Did you try change ram?

[onepic]

Re: Almost dead Lenovo V15-ADA 82C7

Yes, but te same.

[Sephir0th]

Re: Almost dead Lenovo V15-ADA 82C7

If you assume, your board is "full on" then grab a external USB-Keyboard and look whether the CapsLock key is responding when pressing the related key. But if it is "stuck" somewhere and not all necessary voltages are present, then: Without measurements no clue.