Dead Dell Board

[AdrenalinTL]

Hi Guys,

Back again with more learning to do. I would like to start fresh and not confuse myself by looking through different posts.

I have a Cedar Intel Board that is dead. 13269-1 - Seen a few dead boards here on here.

So pls bear with me and let me know if what I am doing is half right as a starting point.



Pin 1 through to Pin 3 measures 19.68V
Pin 4 measures 0.17V
Pins 5-7 measure 0

This below component as well as the area around it worry me though. Almost looks like it was removed and replaced skew? I used a hot air station to clean it as best I could. Result below.



Yeah so again, I am very new to this and just want to find my way around some practical solutions instead of just buying new boards.

Thanks for the help.

[mon2]

Post a higher grade pics for inspection. Also from each angle of the component to view each SMD pad.

Flux the part well and use the hot air tool in a circular motion from the top side. Low air pressure but high heat. Protect the coincell battery by removing it and placing kapton tape to prevent the plastic holder and other nearby parts from melting from the hot air tool. Eventually, this QFN packaged part will swim into place. Inspect each solder pad for shorts and there are any, remove the shorts but fluxing the area and removing the excess solder with desoldering braid.

[AdrenalinTL]

Yeah did all that. Some pins just look like they have corrosion on still.

Best pics I can get.

[mcplslg123]

Do you have any voltage on PL4501/4502? The 4th pin in dc jack is the PS_ID and should be 3.3V but that requires that you must have voltage on PL4501/4502.

The ic which is corroded is not relevant for booting-you can even remove it for the time being as thats the audio IC.

[AdrenalinTL]

cool
yeah 0 voltage on 4501 and 0,56 on PL4502.

Guessing that's not right.

[AdrenalinTL]

Alrighty then.

Obviously one or both PL4501 and/or PL4502 are faulty.

Few questions:

* Where does one buy a replacement? AliExpress has a few 2R2s but they have no codes after that. Any will do?
2R2 full code is 2R2 547 E86. 3R3 full code is 3R3 545 R51. Obviously these mean something but google searching gives me few and far between answers. From google I can now ascertain these are inductors for Power.
* Presume one just solders these off and on again?
* Can 1 be faulty and the other not? e.g. Can the 5V feed the 3V one? None of them appear to be cracked or anything like that.

[reformatt]

PL4501/4502 are inductors, very unlikely to be faulty. They should measure low ohms on a meter. An inductor coil would only ever be faulty if it has shorted turns or is open circuit, something very unlikely in a buck converter like this one. If you have no voltages on the output of these coils, it's generally either because you have a short on the output, or the converter isn't being enabled.

To troubleshoot these kinds of things, you need a methodical approach to troubleshooting. On pg 98 of the 13269-1 schematic, you have a power sequence diagram. The negative numbers on it list the sequence of voltages/enables before the power button is pressed. For example, to get 3D3V_S5 and 5V_S5 (-2) you need S5_Enable (-3) from the EC. But for the EC to be working, you need to the LDO voltage 3D3V_AUX_S5 (-4) from PU4503. For that to be working, you first need DCBATOUT (-5) to be present.

In a nutshell, if a voltage you expect is missing, you first check that rail for a short circuit to ground (with board unpowered), or check whether that voltage is being enabled, and work your way back.

[AdrenalinTL]

OK thanks. Will have a poke around and see what I can figure out.
learning

[mcplslg123]

Resistance to GND on pin3/13 of PU4503
Resistance to GND on PL4501/4502

During measurements, no power attached. If you just removed the adapter,wait for a minute and then proceed to do the measurements.

[AdrenalinTL]

Resistance to GND on pin3/13 of PU4503
Resistance to GND on PL4501/4502

During measurements, no power attached. If you just removed the adapter wait for a minute and then proceed to do the measurements.

pin 3 - 0
pin 13 - 0

PL4501 - 0
PL4502 - 2.71

[reformatt]

Pin 3/13 are the +3V and +5V LDO outputs of PU4503. These are 0 ohms to ground? PL4501 (+5V_PWR) is 0 ohms to ground? PL4502 (+3V_PWR) is 2.71 what? Ohms, Kohms, Mohms?

[AdrenalinTL]

Resistance to GND on pin3/13 of PU4503
Resistance to GND on PL4501/4502

During measurements, no power attached. If you just removed the adapter wait for a minute and then proceed to do the measurements.

Hi,

pin 3 - 0 ohm
pin 13 - 0 ohm

PL4501 - 0 ohm
PL4502 - 2.71 ohm

No power attached.

Pretty sure I did it right. The pins on PU4503 are pretty small but after testing them I kept the ground on the same place and then tried another component and it did measure ... I did it 3 times as well. Measured PL4501 and 4502 quite a few times as well because as you said before, it's unlikely that they are faulty.
I will let you know what exact ohms and test again this evening if I have time. Work just has me flooded right now hence the delays in responding.

[reformatt]

In my experience, multiple shorts on different rails generally means something catastrophic happened on this board. A voltage overload on a rail (like getting 19V on a 3V rail because of a high side MOSFET short), there's often multiple components that will fail. Some boards just aren't economical to repair in that event.

You will have to start removing components (or use voltage injection/thermal camera) to remove the shorts on those rails.

[AdrenalinTL]

Thanks,

Yeah I was going to use this as a test board to learn about the various schematics and things but it looks like it either had water damage, or like you said someone shorted it with a dodgy charger or similar. Wouldn't put it past the guy I actually got it from.

Will perhaps scrap it and use another board as a test. I don't have the machines for voltage injection etc.