LA-E541P no power on

[koby058]

Hi

I have this MOBO, schematic here https://www.badcaps.net/forum/showpo...12&postcount=8

I see that i have no 3v3_ALw nor 5v_ALW. (5V_3V_EN is missing)

I can see that I have 20v on PR303 (current sensor)

the charger IC is isl 88739

resistance on 5v coil is 22.5ohm and on 3.3v coil 16.5ohm

Can you please help me debug it ?

[mon2]

Re: LA-E541P no power on

I can see that I have 20v on PR303 (current sensor)

Unable to locate PR303 - can you check again the label for this component?

I see that i have no 3v3_ALw nor 5v_ALW. (5V_3V_EN is missing)

These ALW rails require the presence of the enables and B+ voltage rails to supply the output rails. B+ is after the 2 x DCin mosfets.

Start with the voltage to ground reading of:

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

of the 2 x DCin mosfets @ PQ740 and also PQ712.

ACOK pin # 2 of PU703 ; voltage to ground ?

To ENABLE each of these 2 x DCin N-channel mosfets, the gate must be higher than the voltage being passed between source / drain pins.

So the gate voltage must be ~25 volts to enable. Otherwise the drain pins on PQ712 (2nd mosfet) should be @ 0 volts.

[mcplslg123]

Re: LA-E541P no power on

Resistance on 3V as well as 5V coil is too low. it should be a few Kohms. PU502,pin15 resistance and PU501,pin17 resistance??

[koby058]

Re: LA-E541P no power on

Hi

I meant PR913 have 20v

Gate is 24.9v and the drain of PQ712 is 20v

ACOK is 20v

PU502 pin15 is 2.4 when on the 200M option of mm
PU501 pin17 is 1.2 when on the 200 option of mm

[mon2]

Re: LA-E541P no power on

The enable for these ALW rails is based on resistor PR506. confirm that this resistor is present. Measure the voltage to ground on both sides of this resistor.

The voltage on ACOK seems very high. This is an open drain output that has a local pull-up resistor (pr741). Confirm again the voltage to ground of this pull-up resistor on the ACOK PIN.

[mcplslg123]

Re: LA-E541P no power on

Clearly +3VLP(LDO) is shorted to Ground. You need to inject 1V at PC509,pin1 with dc supply and observe what is getting hot. Very likely kbc and/or PCH.

[mon2]

Re: LA-E541P no power on

Can you post a pic of your meter face used for the resistance checks? Wish to understand the scale of the measurements.

[koby058]

Re: LA-E541P no power on

Hi

since no board-view, i cannot find PR506 but i can say for sure that ENLDO_3V5V is present on pin 11 of PU501 its 4.5v and on pin 11 of PU509 its 0.49v

It is the 5V_3V_EN on pins 12 of those that is missing.

Pin 2 of charger IC is 20V

On PC509 pin1 i have 1.3ohm resistance

Attached photo of my MM

[mon2]

Re: LA-E541P no power on

See attached. Can you confirm the reading and the meter scale used for this test?

If indeed 1.3 ohms on the 200 ohm scale, then you have a shorted component on this power rail.

As suggested by @mcplslg123, remove all power -> dial up your power supply to 1 volt (never higher to be safe from killing the CPU) & 2-5A.

Then red meter of the power supply on this LDO rail and black power supply lead to ground.

Review which part heats up or even cracks under this event. IPA works well to mist up while the part heats up. It may even be the capacitor @ PC509 but we need to confirm.

Post your updates.

[koby058]

Re: LA-E541P no power on

confirmed

I will push voltages and update

[koby058]

Re: LA-E541P no power on

It took me 3v to get the short to draw 0.4amp. i found out that the EC is getting hot

Is it fixable ? can it be change ? can the job be done without a programmer ?

[mon2]

Re: LA-E541P no power on

dial up your power supply to 1 volt (never higher to be safe from killing the CPU) & 2-5A.

You should have kept the voltage down to 1v but increase the current level of your power supply.

Is it possible that a component near the EC is causing the heat ? Do you have a thermal camera or using IPA ?

[koby058]

Re: LA-E541P no power on

I have a thermal cam, i cannot control the current in the short killer only the voltage.

i felt the EC getting very hot on my fingers

I have this one

https://www.aliexpress.com/item/4001...901b1802RJPde5

[mon2]

Re: LA-E541P no power on

Awesome - we have the same one.

Sounds like the EC is defective but personally do not have experience in this area. Wait on comments from others. If the EC features an external flash device then you only need to replace the EC itself.

[mcplslg123]

Re: LA-E541P no power on

EC is NPCE388XXX and its programmable.So you need a new EC + sio programmer.

[koby058]

Re: LA-E541P no power on

Can the chip be bought already programmed for this computer ?

[mcplslg123]

Re: LA-E541P no power on

Can the chip be bought already programmed for this computer ?

Yes, it can be bought pre-programmed but this facility may not be available iin every country.

[koby058]

Re: LA-E541P no power on

can you point me to it so i can ask?

[mon2]

Re: LA-E541P no power on

@koby058, this guy is advertising this controller and programming services:

https://www.ebay.com/itm/16363203812...H4a9h#shpCntId

You can try also some of the shops on Aliexpress which may be a lower cost.

[koby058]

Re: LA-E541P no power on

thanks, i will ask the owner if he want to invest

thanks all