Dell LA-G341P No power.

[Mbw1a]

Hi!
Need som help left it on battery over night.

After a day or so when i tried to start it up it was complet dead.

I'm not so good at reading schematics but I'm trying.

im missing 3.v line.

PC220 gets really hot. Replaced it but still gets hot.

Sorry for my bad english.

Thanks

[mon2]

Re: Dell LA-G341P No power.

PC220 = capacitor. For the replacement part, what was the capacitor voltage rating ? That is important and must be the proper rating.

[Mbw1a]

Re: Dell LA-G341P No power.

Im replaced it with a 1U_0603_25V6K from another dell motherboard.

[mon2]

Re: Dell LA-G341P No power.

The cap should not be running hot. It is not really required for now. You can remove it off the board till we know more.

With or without the cap, measure & post the voltages on

PU2204 pin 1
PU2204 pin 4
PU2204 pin 5

Meter in DC scale (20V should be ok).

Red meter probe on the pin to test. Black meter probe to ground (shield is ok).

This is a low current buck regulator so it takes a higher INPUT voltage and burns it down to a lower voltage for the output. All this only if the ENABLE pin is active HIGH. So if EN = '1' = ~3v3 (guessing), then this LDO regulator is ENABLED.

[Mbw1a]

Re: Dell LA-G341P No power.

The cap should not be running hot. It is not really required for now. You can remove it off the board till we know more.

With or without the cap, measure & post the voltages on

PU2204 pin 1
PU2204 pin 4
PU2204 pin 5

Meter in DC scale (20V should be ok).

Red meter probe on the pin to test. Black meter probe to ground (shield is ok).

This is a low current buck regulator so it takes a higher INPUT voltage and burns it down to a lower voltage for the output. All this only if the ENABLE pin is active HIGH. So if EN = '1' = ~3v3 (guessing), then this LDO regulator is ENABLED.

PU204:
pin 1: 19,50vdc
pin 4: 8,40vdc
pin 5:0.9vdc

With cap still on. shuld i desolder int and measure?

Thanks for the quick reply!

[mon2]

Re: Dell LA-G341P No power.

Voltage readings for pins 1 & 4 look good.

1 = input

4 = voltage divider to act as the ENABLE pin and based on 300k & 300k (pull-down) = 50% of the input voltage which is about 8v5 - 9 volts.

5 = output pin is not good.

Remove all power. Meter in resistance mode (2k scale is ok).

Measure the resistance to ground of the output pin # 5.

Red meter prove on pin # 5. Black meter probe to ground.

Perhaps something on pin #5 is causing this fault OR just that the regulator @ PU204 is now defective and must be replaced.

First the resistance check of pin # 5.

[bashatm]

Re: Dell LA-G341P No power.

As mon2 said.
But on a side note, are you sure this Cap is not getting hot from another component from the other side of the board? (Isn't the charging section on the opposite layer?) There's no reason for PC220 to get hot, unless it is shorted.

[Mbw1a]

Re: Dell LA-G341P No power.

Voltage readings for pins 1 & 4 look good.

1 = input

4 = voltage divider to act as the ENABLE pin and based on 300k & 300k (pull-down) = 50% of the input voltage which is about 8v5 - 9 volts.

5 = output pin is not good.

Remove all power. Meter in resistance mode (2k scale is ok).

Measure the resistance to ground of the output pin # 5.

Red meter prove on pin # 5. Black meter probe to ground.

Perhaps something on pin #5 is causing this fault OR just that the regulator @ PU204 is now defective and must be replaced.

First the resistance check of pin # 5.

Resistance to ground on pin 5: 232,5K

[Mbw1a]

Re: Dell LA-G341P No power.

As mon2 said.
But on a side note, are you sure this Cap is not getting hot from another component from the other side of the board? (Isn't the charging section on the opposite layer?) There's no reason for PC220 to get hot, unless it is shorted.

im pretty sure its is the cap or pu204. feel nothing on other side.

[mon2]

Re: Dell LA-G341P No power.

I will guess that pu204 is getting hot. It is being ENABLED but there is no output and the output is not shorted.

Sound like pu204 should be replaced. Even with a fresh part, note that this part will be taking a rather high input rail and burning it down to the 3v3 value so it will be a warm to hot in temp component.

You can remove the capacitor to check the source of heat but very likely it is pu204.

Post a pic of this regulator. Perhaps we can cross it with another. AliExpress should offer this device.

[Mbw1a]

Re: Dell LA-G341P No power.

I will guess that pu204 is getting hot. It is being ENABLED but there is no output and the output is not shorted.

Sound like pu204 should be replaced. Even with a fresh part, note that this part will be taking a rather high input rail and burning it down to the 3v3 value so it will be a warm to hot in temp component.

You can remove the capacitor to check the source of heat but very likely it is pu204.

Post a pic of this regulator. Perhaps we can cross it with another. AliExpress should offer this device.

I think you're right. It's probably pu204 that gets hot.
I have lots of motherboards. But finding a similar component may not be so easy. On the motherboards I have.
I would love to buy a new one, but it would have been fun to try it out before.

Thanks.

[mon2]

Re: Dell LA-G341P No power.

So the LDO at PU204 is a high voltage (for input) to fixed 3v3 output at 200mA regulator.

The key parameter is that this part can accept the 19vdc raw which is not so common for the input.

Usually such sot-23-5 parts are max of 6vdc for the input.

Datasheet is attached.

To test out if this is the fault, desolder PU204.

Use your power supply set to 3v3 and current limit it to 200mA. Then apply this dc power supply output onto the PU204 pin #5 to mimic the faulty PU204 regulator.

Still need the dc adapter to power the rest of the logic board.

Be sure to have the common ground from your power supplies.

AliExpress should have the exact replacement for PU204. Be sure it is with the fixed 3v3 output value.

Otherwise, you buy parts from Mouser? Digikey? Arrow?

Here is a vendor we trust and have used them numerous times:

https://a.aliexpress.com/_msKshBA

[Mbw1a]

Re: Dell LA-G341P No power.

Sorry for the late reply.

Replaced Pu 204 and now I have 3.3 volts .

But won't start..🙁 I don't have 3.3v on pu200. I'm completely lost.. don't know where to start looking now.

[mon2]

Re: Dell LA-G341P No power.

1) Post the voltage readings of pins 1, 2, 3, 4, 8 of PU200.

2) Post the voltage readings of the requested points for the 3v rail - see attached.

[Mbw1a]

Re: Dell LA-G341P No power.

1) Post the voltage readings of pins 1, 2, 3, 4, 8 of PU200.

2) Post the voltage readings of the requested points for the 3v rail - see attached.

Pu200:
pin1:001V
pin2:0V
pin3:1,721V
pin4:0V
pin8:0V

PQ226:
0V
Pr266:
0V
Pr271:
0V

Could it be the super io chip that is broken?

[mon2]

Re: Dell LA-G341P No power.

Voltage @ pin # 5 of PU204 ?

[Mbw1a]

Re: Dell LA-G341P No power.

Voltage @ pin # 5 of PU204 ?

3.3v

[mon2]

Re: Dell LA-G341P No power.

PU400, pin # 7 creates the ALW_PWRGD_3V_5V signal.

Since ALW_PWRGD_3V_5V is LOW, the power is NOT good for both the 3v and 5v rails @ PU400 IC.

Post the voltage @

PL400, pin 1

PU400, pin 6

PL401, pin 1

[Mbw1a]

Re: Dell LA-G341P No power.

PU400, pin # 7 creates the ALW_PWRGD_3V_5V signal.

Since ALW_PWRGD_3V_5V is LOW, the power is NOT good for both the 3v and 5v rails @ PU400 IC.

Post the voltage @

PL400, pin 1

PU400, pin 6

PL401, pin 1

Pl400:0V
Pl401:0V
PU400 pin 6:001V

[mon2]

Re: Dell LA-G341P No power.

PU400 pin 6:001V

Confirm that there is a connection from PR326, pin #2 & PU400, pin # 6.

Meter in 2k scale, meter probe on pin # 2 (PR326) & other meter probe @ PU400, pin #6. Just trying to confirm if the 0 ohm resistors are present or they could even be solder blobs.

Next, check the voltage on both sides of PR326.

The 3V/5VALW_EN signal is created by UE3, ball A5.

Confirm the voltage of +RTCBATT.