Dell E5530 completely dead and MOSFET getting HOT! Please help.

[roxboy1984]

Hi,

So I'm trying to fix the above mentioned dell laptop. It has no signs of life at all when plugged in. If I connect the AC I noticed the MOSFET PQ5 gets very hot. So I'm assuming there is a short somewhere. I'm still learning so please could someone assist me. Thanks for any help given.

I did try swopping the Mosfet which is a AO4423 with one from a donor board being a SI4483ADY as they both have the same VDS @ 30V. once I swopped the Mosfet when I plugged in the charger it would just switch off so I swopped the MOSFET back.

[FrozenHaxor]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Measure the MOSFET between Drain and Source while it's unsoldered, is there a short on the meter in diode mode in both directions?

Are you able to measure total power consumption of the whole board? I.E. by connecting it to a lab power supply.

When MOSFET is desoldered, measure point +DC_IN_SS to ground in diode mode, is there a short? If There is, inject a small voltage, no more than 1,5V to start with and check what gets hot.

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Measure the MOSFET between Drain and Source while it's unsoldered, is there a short on the meter in diode mode in both directions?

Are you able to measure total power consumption of the whole board? I.E. by connecting it to a lab power supply.

When MOSFET is desoldered, measure point +DC_IN_SS to ground in diode mode, is there a short? If There is, inject a small voltage, no more than 1,5V to start with and check what gets hot.

Thankyou for your reply. I will do as you suggested and report back.

I do have a lab power supply. Please excuse my ignorance but how do I measure total power consumption using it?

With voltage injection. Where would I inject the voltage from exactly? Black probe on ground and red probe on what component. I know this is probably a very noob question but I've never done it before. Thanks again for the help.

[FrozenHaxor]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Thankyou for your reply. I will do as you suggested and report back.

I do have a lab power supply. Please excuse my ignorance but how do I measure total power consumption using it?

With voltage injection. Where would I inject the voltage from exactly? Black probe on ground and red probe on what component. I know this is probably a very noob question but I’ve never done it before. Thanks again for the help.

You can get a raw cable that is being used with Dell power bricks, connect that to lab power supply, set to 19.5V then connect to laptop and observe the drawn current on the power supply. If it maxes out and goes into constant current mode then it's a true short.

As for voltage injection, Inject the + on the marked point where MOSFET resides, removing the MOSFET is not mandatory to do this unless it's shorted out. Remember no more than 1.5V to start with, we don't know if for example a part of supply of CPU or other low voltage part like PCH is not shorted and we don't want to damage the delicate part. If current draw is very low or you can't detect the heat from the shorted component, you can gradually increase the current on the lab power supply until you get to about 2A, you should be able to detect the heat then.

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

You can get a raw cable that is being used with Dell power bricks, connect that to lab power supply, set to 19.5V then connect to laptop and observe the drawn current on the power supply. If it maxes out and goes into constant current mode then it's a true short.

As for voltage injection, Inject the + on the marked point where MOSFET resides, removing the MOSFET is not mandatory to do this unless it's shorted out. Remember no more than 1.5V to start with, we don't know if for example a part of supply of CPU or other low voltage part like PCH is not shorted and we don't want to damage the delicate part. If current draw is very low or you can't detect the heat from the shorted component, you can gradually increase the current on the lab power supply until you get to about 2A, you should be able to detect the heat then.

Thanks for the info. so I did as you suggested and these are the results.

I removed the Mosfet measured in Diode mode I get 0.187 from source to drain and vice versa.

I tried injecting 1.5V but i couldnt feel anything getting hot. I will try increasing and test again.

I didnt have a Dell Power brick to kill so i set power supply to 19.5V and put the red probe on the Positive where the DC jack is and the picture is the result.

[mon2]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Remove all power. Meter in resistance mode.

What is the resistance to ground of the source pins on PQ5 ?

Resistance to ground of the drain pins of PQ5 ?

You are drawing 87 mA of current which is very low so the logic board is not being powered.

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Remove all power. Meter in resistance mode.

What is the resistance to ground of the source pins on PQ5 ?

Resistance to ground of the drain pins of PQ5 ?

You are drawing 87 mA of current which is very low so the logic board is not being powered.

Source to ground is 7.5 Kilo Ohms
Drain to ground 7.68 Kilo Ohms

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

I also removed PQ5 and injected 2Amps and nothing is getting hot. even borrowed a thermal cam and cant see anything getting hot.

[FrozenHaxor]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

I also removed PQ5 and injected 2Amps and nothing is getting hot. even borrowed a thermal cam and cant see anything getting hot.

What's the voltage going while you have 2A of current? If it's low like 0,5V then bump up the current. Most of the power probably gets lost in the leads.

[mon2]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

The issue may also be that you are not able to properly emulate the PS_ID that is required for the Dell boxes. With your bench power supply, the PS_ID single wire communication to the logic board is missing.

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

What's the voltage going while you have 2A of current? If it's low like 0,5V then bump up the current. Most of the power probably gets lost in the leads.

The board is taking 1.09V and 2amp.

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

The issue may also be that you are not able to properly emulate the PS_ID that is required for the Dell boxes. With your bench power supply, the PS_ID single wire communication to the logic board is missing.

Does this mean that i need to find a dell Adapter and cut off the jack and connect it to my bench psu?

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Ok so after i injected more current and checked with thermal cam i found a ceramic capacitor that was getting hot so i swopped that out and now when i inject voltage it went from accepting 1.5v and 2 amps to 1.5v and 0.003 amps. What does that mean? good or bad? Thanks

[mon2]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Very good. So you have found and removed a shorted cap.

This is with the mosfet removed (PQ5) ?

While PQ5 is removed from the logic board, confirm that it is not defective if you have not done it already.

Meter in resistance mode, no power, check:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)


Post the readings and scale used on your meter for the measurements.

If you have a low resistance reading then the mosfet may be defective. If the resistance values are ok -> solder it back onto the board. Once the power path is complete, the power consumption should be higher.

That is, this mosfet likely was heating up due to the shorted cap you have found. Good job!!

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Very good. So you have found and removed a shorted cap.

This is with the mosfet removed (PQ5) ?

While PQ5 is removed from the logic board, confirm that it is not defective if you have not done it already.

Meter in resistance mode, no power, check:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)


Post the readings and scale used on your meter for the measurements.

If you have a low resistance reading then the mosfet may be defective. If the resistance values are ok -> solder it back onto the board. Once the power path is complete, the power consumption should be higher.

That is, this mosfet likely was heating up due to the shorted cap you have found. Good job!!

Thanks again for all the help. so i took a chance and connected things back up to test with the AC plugged in and i noticed the following under the thermal cam.

the following in the pics get hot.

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Ok so i swopped out PQ5 which is a AO4423 MOSFET with a VDS of 30V with a MDS3604URH MOSFET which also has a VDS of 30V. Now PQ% no longer gets hot but PQ1301 & PQ1302 get very hot.

Do you think perhaps they are bad? i cant read whats written on them to try and find a substitute.

[mon2]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

PQ1301 & PQ1302 get very hot.

Yes, perhaps damaged but they are acting like SPST switches to allow for the charger IC to measure the current being consumed by the main logic board power rail. The charger IC is measuring the voltage drop across the current sense resistor @ PR1301.

Respectively, these mosfets should not be getting hot unless there is some excessive loading event.

Remove all power -> meter in resistance mode.

Measure the resistance across:

source & drain
source & gate
gate & drain

pins of each mosfet. Post their measurements.

The part is a jellybean P-channel mosfet and can be replaced with many others.

The following should work fine:

https://www.digikey.com/en/products/...03TRPBF/812496

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Yes, perhaps damaged but they are acting like SPST switches to allow for the charger IC to measure the current being consumed by the main logic board power rail. The charger IC is measuring the voltage drop across the current sense resistor @ PR1301.

Respectively, these mosfets should not be getting hot unless there is some excessive loading event.

Remove all power -> meter in resistance mode.

Measure the resistance across:

source & drain
source & gate
gate & drain

pins of each mosfet. Post their measurements.

The part is a jellybean P-channel mosfet and can be replaced with many others.

The following should work fine:

https://www.digikey.com/en/products/...03TRPBF/812496

Ok so these are the measurements of those two mosfets.

PQ1301
source & drain = 106 ohms
source & gate = 106 ohms
gate & drain = 5.76 Kilo ohms
PQ1302
source & drain = 106 ohms
source & gate = 104 Kilo ohms
gate & drain = 0.5 ohms

[mon2]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Both look too low in the readings.

Carefully remove each and measure them when they are out of the circuit to confirm the readings are consistent. They appear to be defective based on the thermal view and the low resistance readings.

[roxboy1984]

Re: Dell E5530 completely dead and MOSFET getting HOT! Please help.

Both look too low in the readings.

Carefully remove each and measure them when they are out of the circuit to confirm the readings are consistent. They appear to be defective based on the thermal view and the low resistance readings.

Thanks i shall do that and post back a bit later. is there anything i need to take note of when swopping them out from a donor board if they are faulty? other than VDS?