acer a515-52g-4830 5valw 3valw missing

[Kshi]

hello,
this is my third time trying to revive dead laptops.
I got this acer does not have power light

First I test
dc 19v-ok but +5valw and +3valw is missing
i remove the board to test more but i didnt find anything
no shorts no corrosion

but i get +3vlp and +5vlp present
and now i dont know what to do anymore

hope someone can help me and improve my skill

Link to schematic - https://www.badcaps.net/forum/troubl...hematic-needed

[mon2]

dc 19v-ok but +5valw and +3valw is missing
but i get +3vlp and +5vlp present

The LP and ALW rails are linked to the same controllers. There should be a 3v3 regulator and another for the 5v rail.

Remove all power. Measure the resistance to ground of each of the missing rails = ALW rails. If there is a lower than normal resistance, there is a fault on that rail. If the resistance is ok, check if the EN = enable signals are present for the respective ALW rails.

[Kshi]

So I test the 1st mosfet source and drain and i found that is short so i remove it and found a jumper wire below the chip.

I replaced the 1st mosfet but now i get
Drain 19v
source 0v
gate 0v
maybe the charging ic is busted because of jumper on first mosfet?

[mon2]

The tech before you placed a wire to bypass the mosfet? Hack. If this could be justified, the vendor would certainly consider the same reduction in the bill of materials to increase their profits. Rarely would I agree to bypass such parts.

Remove all power. Measure the resistance across the 2nd DCin mosfet @ PQ311:

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

Post each measurement. Each measurement should be high hundreds of k ohms or higher else the mosfet is a suspect.

[Kshi]

This is the measurement i got at PQ311
Source- ol
Gate- ol
Drain- 4.5kohms

1st mosfet is
Source- ol
Gate- ol
drain- 330kohms

[Kshi]

I remove the 2nd mosfet and it seems to be working fine, this what im getting now without it

PQ311
Source ol
Gate ol
Drain 4.5k

I think one of this mosfets is the problem?

PQ312
Source 520k
Gate ol
Drain 4.5k

PQ305
Source 520k
Gate 520k
Drain 4.5k

or the charging ic is broken?

[mon2]

Sorry. Measure the resistance as:

source & drain
source & gate
gate & drain

post each measurement. No power to the board during these checks.

[Kshi]

Pq 310
source & drain 400
source & gate 500
gate & drain ol

PQ311
source & drain 450ohms
source & gate 500ohms
gate & drain ol

[mon2]

These are very low measurements for a good mosfet. Start with removing PQ311 off the board. Flux and remove. Then allow it to cool down and then test the removed mosfet again using the same method. Are the measurements still this low? A good mosfet should be hundreds of k ohms or higher.

If the readings remain low, replace the mosfet. Proceed to test PQ310 again with PQ311 removed. Repeat to replace if the measurements remain low.

Based on the measurements, it appears that both mosfets are defective.

Be sure to measure the resistance to ground of PQ311 (drain pins = 5-6-7-8) = +19V_P2. If this main power rail is low then there is a shorted part onboard and causing the DCin mosfets to die.

[Kshi]

After removing pq311 I get ol in ohms measurement of all s&d s&g g&d pins
but in diode mode the measurement of souce and gate is 400

I remove pq310 same pinout measurement but in diode mode of g&s is 400

is this normal? Or shoul i have value of the pinout in ohms mode

[mon2]

OL means over limit.

Is your meter auto ranging or manual select for the resistance scale? Switch to a higher resistance scale till you see a measurement.

Post the resistance values in ohms. Your scale may be k ohms for example, etc.

[Kshi]

Its manual select 2m,200k,2k,200 I tried all settings but not measuring any

tried to remove 1st mosfet on donor board and i got readings on it

[Sephir0th]

O.L. is fine but only when assuming you made proper contact with your probes. The value in diode mode proves that the Mosfets have not failed open beside diode mode is not suitable for normal resistance measurements.

Since a shorted Mosfet normally wouldn't prevent the voltage from passing the 1st Mosfet from Drain to Source, it's time to inspect the charging controller. Most likely the ALW are not coming up, the charging controller doesn't inform the EC via ACOK.

And i strongly suggest to inspect other possible related spots for previous work.

[Kshi]

O.L. is fine but only when assuming you made proper contact with your probes. The value in diode mode proves that the Mosfets have not failed open beside diode mode is not suitable for normal resistance measurements.

Since a shorted Mosfet normally wouldn't prevent the voltage from passing the 1st Mosfet from Drain to Source, it's time to inspect the charging controller. Most likely the ALW are not coming up, the charging controller doesn't inform the EC via ACOK.

And i strongly suggest to inspect other possible related spots for previous work.

this is the measurement i got on charging ic
ACIN_CHG 4.50v
AC_IN 0.05v
EC_SMB_DA1 0.02v
EC_SMB_CK1 0v
N16860695 0v
AMON_ISL955 0v
BMON_ISL955 0v
N16860688 0v
PROG_CHG 0v
COMP_CHG 0v
CCLIM_CHG 1.6v
FSET_CHG 0v
N16860560 0v
CSON_CHG 0v
CSOP_CHG 0v
ACLIM_CHG 1.3
N16860799 0.92v
N16860474 18.7v
VDD_CHG 5.2v
VDDP_CHG 5.2v
LG_CHG 0v
LX_CHG 0v but sometimes unstalbe 3v to 0v
UG CHG 0.6v
BST_CHG 4.8v
BGATE_CHG 4.2v
VBAT_CHG 0v
OPCP_CHG 4.8v
OPCN_CHG 0.06
CMSRC_CHG 0v
ASGATE_CHG 0v
CSIN_CHG 0v
CSIP_CHG 0v
GND

I cant see any previous work done maybe they only jump 1st mosfet? then jumping that eventually
blown the charging ic?

[Sephir0th]

Add at least the Pincount or even better, add the correct designations from the schematics. To use the boardview as reference is not sufficient here.

[Sephir0th]

EC_SMB_DA1 and EC_SMB_CK1 missing implicates that not only the +3VLP is missing but +19VB too. In your initial post you wrote it is present.

Of course such mistakes can lead the approach into the wrong direction. But it's fine since it was advised to check the charging controller anyway. Correct DCIN, ACIN, VDD and VDDP voltage in combination with no ASGATE to drive the Mosfets normally means a dead charging controller... except the Mosfets were replaced with wrong parts.

other subtle faults are possible too, like PR304, PR305 failed or low resistance at VDD/VDDP. Yes, voltage measurements are not enough and reveal only half of the picture. We need resistance measurements in addition.

[mon2]

AC_IN 0.05v

Review this. This is mated to ACOK on your charger IC pin # 2.

Measure the voltage on PR311.

Remove all power. Measure the resistance across PR311.

ACIN pin #1 has a valid adapter voltage (ACIN_CHG = 4.50v). Based on this voltage, ACOK should be floating since this is an open-drain output. When the line is floating, the 2 resistors @ PR311 & PR313 will build a voltage divider to park this floating line. At this time, the AC_IN signal line is @ 0v. If the charger truly does not like the adapter voltage, the charger IC will pull this line to the logic low = 0v but to me, it is ok and there should be a valid voltage here unless the parking resistors are missing or of the wrong values.

[Kshi]

Sorry for the confusion on my post. +3VLP and +19VP were present before I found a jumper wire below the first mosfet. I replaced the mosfet, and now 19V is not passing through the first mosfet. The problem I have now.

I use mdu1511 to replace EMB04N03H. I don't really think if this is compatible.
I attached value of each mosfets

The resistance of PR304 is 0 ohm, and PR305 is 1.5 ohm. The measurement of VDD to ground is 90k ohms.
Is it that one of the resistors is faulty?

[Kshi]

Review this. This is mated to ACOK on your charger IC pin # 2.

Measure the voltage on PR311.

Remove all power. Measure the resistance across PR311.

ACIN pin #1 has a valid adapter voltage (ACIN_CHG = 4.50v). Based on this voltage, ACOK should be floating since this is an open-drain output. When the line is floating, the 2 resistors @ PR311 & PR313 will build a voltage divider to park this floating line. At this time, the AC_IN signal line is @ 0v. If the charger truly does not like the adapter voltage, the charger IC will pull this line to the logic low = 0v but to me, it is ok and there should be a valid voltage here unless the parking resistors are missing or of the wrong values.

PR311 reading is 65Kohms
in ground 95K ohms in both legs

[mon2]

Confirm that VDD_CHG is present on the one side of PR311. This is important. Measure this voltage to ground.