Have a dead short on the DCBATOUT side of this board. PU4308 became very hot when I applied current to dcbatout pad of PR4002. Removed 4308 (p. 43), short gone, but pins 1-3 on board still short. Removed PL4303 and pins of PU4308 no longer short. So also removed PL4302 and 4303. VCC Core side of all 3 coils are short. Put current to one of the pads, shows short for sure but can't find smoking gun. Is it one of the caps (ST330U2V, 6 in all) right after the coils? Or one of the caps on page 8 (left hand side of page)? Am I on the right track?
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Re: Dell N5050 dead short
Turned out to be one of the large black caps, ST330U2V, PT4308 I think. Short completely gone. Replaced with one off a scrap board, soldered everything back on and board shorted again as soon as plugged in. Removed all 6 caps again but this time in different order and the one I removed last eliminated the short. But it wasn't 4308 this time. Is there something I should know about replacing these caps that I'm missing? Coincidence both times that last cap removed eliminated the short? Because I checked for short after removing 1 cap at a time... -
Re: Dell N5050 dead short
It is usually over voltage that causes capacitors to go short. Usually kills the CPU also. Do the capacitors still measure shorted after removed from the PCB?
PU4308 must have been shorted or on also.Comment
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Re: Dell N5050 dead short
Yes, PU4308 was dead too. None of the caps measure short after removing from the board. Can I replace PU4308 and try to plug in the board without those 6 caps just to verify they're the problem? Probably not a good idea if they're not. I've got a DC power supply too, maybe I can slowly raise the voltage? Not sure how to proceed, just know I want to eliminate those caps as the problem.Comment
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Re: Dell N5050 dead short
Plugged board in with no caps, no short! Even got a blinking power light and have 3v and 5v at coils. Will go no further until I can figure out this cap issue. Used hot air to remove and install, is that a no-no for this type?Comment
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Re: Dell N5050 dead short
It is all a puzzle. Capacitors of any type usually don't become good again after going short.
Judging by what I have seen others do, these capacitors tolerate a lot of heating. People including myself used to get misled into thinking a short was present because of the normal 4 to 6 ohms of the CPU. An I5 CPU I measured lately seemed to be over 100 ohms.
How do you define a short?
I can't find a full data PDF for the controller IC. Most of them have crowbar protection where the low side MOSFETs are turned on to keep Vcore clamped when certain faults occur that try to make Vcore too high.But this will not show as a short while all inductors
are removed.
There can also be a pin on the IC connected directly to the Vcore that is able to clamp to ground. So you might measure a few ohms to ground which can remain long after power is removed. Before you know it, the short is gone.
The shorted high side MOSFET is likely to have been the only fault.Last edited by rievax_60; 11-21-2015, 02:32 PM.Comment
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Re: Dell N5050 dead short
I installed a CPU, plugged the board in and it shorted again, blowing PU4308. Removed PU4308 and PL4303. VCC Core side pad of PL4303 measures about 1 ohm to ground. With my power supply set to 1 volt and 2 amps on that pad, I measure 1 volt and about 1.65 amps. I know a dead short would show no voltage and 2 amps and no problem would show 2 volts and 0 amps. So what is my power supply showing me?Last edited by p1muserfan; 12-13-2015, 08:53 PM.Comment
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Re: Dell N5050 dead short
1 volt and 1.65 amps indicates about 0.6 ohms and 1.65 watts of heating somewhere.Comment
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Re: Dell N5050 dead short
Found it, it was PU4307, replaced, so now I'm back to having 3,5v power to the board with nothing installed. With no power to the board and no CPU installed, I'm measuring pretty high resistance to ground on the 3 CPU power coils. With a CPU installed I measure about 16 ohms, which I understand to be about right. So is my chipset ok? Hate to keep installing a CPU and having the board short every time I plug it in, is there something else I can check?Comment
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Re: Dell N5050 dead short
What I call Vcore, is called VCC_CORE in the schematic. I had trouble lately with a Lenovo.
The Vcore was going to 6v because of a fake ADP3212 controller IC I put in. It made the I5 CPU go short circuit. The Lenovo would turn on the Vcore rail without the CPU fitted. I caught the rail going to 6v for a short time before shutting down with a DSO.
As a precaution I rats nested a crowbar protector that I soldered across the Vcore rail that was set to trip at 1.5v.
When I fitted a good ADP3212, new MOSFETs and CPU, it all just worked, the crowbar did not need to trip.
I cant see any other safe way to test it. Ill say more if I think of something.Comment
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Re: Dell N5050 dead short
Still in need of some help here. Have standby voltage and white power light on an empty board (no CPU or memory installed) only because PT4301,2,3,4,8 and 9 are removed. If they're installed, board shorts immediately. Why? Because I measure 19v across PL4301,2 and 3. Isn't that voltage only suppose to go as far as the upper fets (PU4302,5, and 8)? This can't be goodComment
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Hi All, I have a 9th Gen Dell Optiplex micro PC motherboard which doesn't power on. When I connect the motherboard with power adapter, it goes into safe mode and turns off. So from info I have gathered online, it looks like there is a short circuit on the motherboard. So can you guys help me with figuring out the issue?
I am new to electronics repair, so my queries could be naive but I am ready to learn.
So I have a multimeter and a solder with me. But I can try to get a variable voltage power supply with a thermal camera as well. From what I seen online, best way is... -
My question pertains to understanding the control circuity inside a Dell PT434 type battery used in Dell E6400, E6410 and other Dell notebooks?
Does anyone have a circuit diagram for the inside of a Dell PT434 battery and/or a description of how the control lines work to control this battery?
My reason for asking is I have a battery which I cannot get to charge beyond 1% in a Dell E6410 or E6400.
The LED bar graph charge indicator on the battery shows one LED lighted when the info button is pressed.
I have tried multiple different Dell power adapters. My Dell... -
Hi guys!
I searched for the term "dead short" in the forum but no specific thread came up however if I'm just blind and couldn't see the thread talking about this please forward me to that direction.
So my problem is I don't know how to find the source of a dead shorted voltage rail. Dead short = ~0 ohm resistance.
I have two VGAs (HD 4850 and HD 4870), both dead shorted to ground on the memory rail. I have the boardview file for the 4870 and the memory rail consists around ~7892346 capacitors...
I have a bench PSU and if I try to inject voltage the voltage... -
Hi all,
I have recently picked up this Dell OEM Nvidia GTX 750Ti 2GB Video card. Its an old card I know but still wanted to get it working if possible. The problem is the following:
- Put the card in my testing motherboard and start running Heaven benchmark
- Benchmarks seems to run smoothly up until half way then the motherboard completely shuts off immediately
- Try to start it again and I get a slight move from the PSU fan - a clear short
- A little troubleshooting later I find one shorted Mosfet - Replace them both - short is gone
- Put the... -
the comon problem they say , the charger will shut off power once plugged to laptop , i dont have battery, its long gone ago , i use it for backup with adapter and vga port to external monitor(yes no screen lcd) in case my desktop needs fix . one thing for sure i could say the clr resistor - r010 beeps ,short at both sides , the checked all the coils , the 3 coils together gives all of them beeps short along with their respective capacitors . i dont have voltage ampere injection dc machine as in videos i have seen they see where its getting hot and they remove the short and replace components...
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