Platform : (wistron_berry_dg15_intel_discrete_uma)

Urgent help is needed.

Got dead Dell N5010 UMA for repair.

Replaced failing ISL62883HRT +shorted VCC_CORE and +VGA_CORE outputting fets.

Now :
When plugged in, adapter light shuts immediately and PTC4702-PTC4703-PTC4706- PTC4707 ( +VCC_CORE outputting electrolytic caps) short at once.
Fixed 4 new caps, they short again.

What is likely to make the 4 electrolytic caps short and short again, knowing that ISL62883HRT was already replaced ??? Where to dig further ?

Thanks

Check again PU4702 and PU4703. I`m pretty sure PU4702 is in short. Otherwise PU4701 wasn`t properly soldered on place and you have a break between pin 20 of pu4701 and pu4702`s gate.

Ok, checked PU4702, found it short again, though PU4702-4703-4704-4705-4707-4708 were already replaced. Removed PU4702 and measured Resistance to GND on PL4701, found 87 Ohms with CPU installed, very low!

Removed one leg of each coil i.e PL4701 PL4702 PL4703, found with GREAT SURPRISE over 0.180 kohms resistance to gnd before and after the coils;
Re-soldered coils, and measured again coils'resistance to GND found 0.220 kohms that's ok!

But couldn't understand why coils'resistance to gnd became normal, just after removal of one leg and resoldering it back ? I guess some discharge took place when legs were removed!

Further to my last post, replaced PU4702 and faulty caps and powered lap, without CPU, fan spinned for 30 seconds then stops and lap switched off !!!
Found the 6 caps and fet PU4702 just replaced shorted again with PU4703!!!

Have to trace and figure out what is causing repetitive short to caps and fets before powering it again.

QUESTION : Is there a method for trying on lap without risking a new short for fets and caps replaced, that will be very helpful ???

Hi 0D1N,

I put aside Dell n5010 under repair since last week (Aïd, our religious celebration), so couldn't give any feedback earlier!

Anyway, thank you for the scheme. I totally agree with your good explanation regarding what causes caps and fets to be shorted and wish to add that failing processor and load faults are also to be considered.

As said in my last posts, PU4701 and PU4702 were already replaced. Also, they're checked to be properly soldered and Ugate1 of PU4702 properly linked to pin 20 of PU4701.

UPDATE :
It turned out that PU4706 was shorted (3rd phase VCC_core output).
New steps taken :
-Replaced PU4706 and all shorted caps and fets.
-Removed PU4707 and PU4708 to help identify which output Phase is causing immediate short.
Powered lap without CPU, adapter shut down immediately!
Found shorted for this time, only :
PTC4702 , PTC4704 and PTC4705
All fets are checked OK. improvement !!!

Now have to trace out what is causing PTC4702 alone (PHASE1) with PTC4704, PTC4705 (PHASE2) to fail again ?

Any suggestion is welcome.

Add :

Sorry, didn't find the right way for attaching image to my last post. It's the 1st time I upload photo to this forum. So, unfortunately, image inserted couldn't be enlarged.

P.S note that circled components, are the 3 shorted caps, also "not installed" marking is for removed fets PU4707 and PU4708 (PHASE3).