Repeated short circuit. P channel mosfet keeps blowing up

[IamPritesh]

Hello friends, hope everyone is safe and healthy in this pandemic.

So I have this Dell 3521 ( LA-9104P ) which has this strange issue of short circuit coming even after replacing the failed component,
THe short always happens on the 1.5V line and everytime it shorts a different component on the same line including the second mosfet.

So I first replaced the IC on PU300 (RT8207)

First it instance ( PQ101, PQ300, CD39)
Replaced both mosfet and removed the capacitor..
Second instance ( PQ101, PQ300, CD14)
Replaced both mosfet and removed the capacitor..
Third instance ( PQ101, PQ300, PC308)
Replaced both mosfet and removed the capacitor..

And now we have this ( PQ101, PQ300, QC3) as shorted.

Please advise how to find the real cuplrit.


Schematic attached for reference .Thanks

[peste]

Re: Repeated short circuit. P channel mosfet keeps blowing up

Hello friends, hope everyone is safe and healthy in this pandemic.

So I have this Dell 3521 ( LA-9104P ) which has this strange issue of short circuit coming even after replacing the failed component,
THe short always happens on the 1.5V line and everytime it shorts a different component on the same line including the second mosfet.

So I first replaced the IC on PU300 (RT8207)

First it instance ( PQ101, PQ300, CD39)
Replaced both mosfet and removed the capacitor..
Second instance ( PQ101, PQ300, CD14)
Replaced both mosfet and removed the capacitor..
Third instance ( PQ101, PQ300, PC308)
Replaced both mosfet and removed the capacitor..

And now we have this ( PQ101, PQ300, QC3) as shorted.

Please advise how to find the real cuplrit.


Schematic attached for reference .Thanks

measure the 1.5v rail and see if it is short, with the L300 removed ... inject 1.5v, 3-5A in point 1 and see if something heats up ...

[IamPritesh]

Re: Repeated short circuit. P channel mosfet keeps blowing up

measure the 1.5v rail and see if it is short, with the L300 removed ... inject 1.5v, 3-5A in point 1 and see if something heats up ...

I inject voltage and found one component heated up like the examples given above. I remove it then shorting is removed and next when I PLUGIN THE ADAPTER again some new component gets shorted .

[mcplslg123]

Re: Repeated short circuit. P channel mosfet keeps blowing up

did you replaced PU300 with exact match?? Only matching RT8207 wont do, suffix also needs to be matched. Btw RT8207MZQW=Richtek code J7

[IamPritesh]

Re: Repeated short circuit. P channel mosfet keeps blowing up

did you replaced PU300 with exact match?? Only matching RT8207 wont do, suffix also needs to be matched. Btw RT8207MZQW=Richtek code J7

Thanks for your reply.Hope you are doing well sir.
Replaced from the same donor board and they are identical. I have never encountered this before thus pretty much annoyed at myself . The moment I remove /replace shorted component, and plug the adapter, the fan spins for a second and then adapter light goes off.
Something is triggering the short circuit over and over again.

[Duranitron]

Re: Repeated short circuit. P channel mosfet keeps blowing up

Hello friends, hope everyone is safe and healthy in this pandemic.

So I have this Dell 3521 ( LA-9104P ) which has this strange issue of short circuit coming even after replacing the failed component,
THe short always happens on the 1.5V line and everytime it shorts a different component on the same line including the second mosfet.

So I first replaced the IC on PU300 (RT8207)

First it instance ( PQ101, PQ300, CD39)
Replaced both mosfet and removed the capacitor..
Second instance ( PQ101, PQ300, CD14)
Replaced both mosfet and removed the capacitor..
Third instance ( PQ101, PQ300, PC308)
Replaced both mosfet and removed the capacitor..

And now we have this ( PQ101, PQ300, QC3) as shorted.

Please advise how to find the real cuplrit.


Schematic attached for reference .Thanks

encounter this problem with hp laptop it destroy all the mosfets that is inline with processor vcore the moment you power it on. shorted mosfets replaced with new it shorted out what i did is check very well all the buck capacitor. i replaced a 330uf that checked fine with testers even with esr meter but in circuit it trickle a short not dead short but just trickle short.. i pulled out all the capacitor and test it out using just voltage to load the cap then use a oscilloscope and you will see the cap shorting out randomly. try to place new capacitor and new coil specially the 1R0 or 36R, just try it..

[IamPritesh]

Re: Repeated short circuit. P channel mosfet keeps blowing up

encounter this problem with hp laptop it destroy all the mosfets that is inline with processor vcore the moment you power it on. shorted mosfets replaced with new it shorted out what i did is check very well all the buck capacitor. i replaced a 330uf that checked fine with testers even with esr meter but in circuit it trickle a short not dead short but just trickle short.. i pulled out all the capacitor and test it out using just voltage to load the cap then use a oscilloscope and you will see the cap shorting out randomly. try to place new capacitor and new coil specially the 1R0 or 36R, just try it..

Thanks for sharing your experience. . Buck capacitors.. you mean polarized capacitors ?

[Shrimp_Green]

Re: Repeated short circuit. P channel mosfet keeps blowing up

Hello, greeting from Brazil.
Short on high mosfet is dangerous, not good at all. If the 19v B + arrived at 1.5V it may have damaged components in that line. For example ram. Replace the ram.

Always replace the pair of mosfets, in the case of PQ300 and PQ301.

Attention to the 1.5V line, check if there is no short

[Duranitron]

Re: Repeated short circuit. P channel mosfet keeps blowing up

Thanks for sharing your experience. . Buck capacitors.. you mean polarized capacitors ?

yah.. 330uf , 220uf or 100uf polarized cap..