Dell 1525 DS2 Intel Tps51120 faulty or not?

[lezsimply]

Good day. I need to confirm if TPS51120 (U56) is faulty or not. 3.3v present on vreg3 pin no.19 and 5v present on vreg5 pin no.21

But no voltage present on L6 (5v_alw) and L7 (3.3v_alw) No voltage output from U26 U28 U29 and U32.

As what I have understand 5v_alw comes out from U26 and U28 fets. 3.3v_alw comes out from U29 and U32 fets. All 4 Fets acquire power from TPS51120 (U56) of pins no. 14,16,25 and 27 through gate (correct me if I'm wrong guys)

Laptop is totally dead but receives power from adapter. battery no longer working. DC jack is ok too.


Here are some voltages present

3.27v present on power button
3.30v present on pin no.8 of U21
3.06v present on rtc1

This is the schematic I found. Hope you guys guys can help out. Thanks very much!

[whaldsz]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

Check first if pin 15 of SIO is high.

If not, reflash U21 or change SIO.

[lezsimply]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

No voltage on pin 15 (S5_enable) and pin 16 (RSMRST) of SIO chip. I suppose to have voltage here when power button is pressed?

And also is it normal to have voltage present on L14 coil approximately 1.80v when there is no adapter or battery attached? This voltage slowly drops until it reaches 0 when I put meter on it. Tested this coil and its not shorted. Voltage also present on U5, R204 and C375 of battery circuit. Thanks again.

[lezsimply]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

In the image below how would I test this component circled in red if its open or not? I know its a diode but I can't seem to find datasheet for it.

Just curious because I only get 19v on one side unlike on some acer and hp netbooks diodes have voltage on both sides. The reason for asking is because dc jack has 2 pins for positive (19v) which separates along the way. The other is connected to this diode labeled D2. I don't have any diagram of the other board labeled DS2 LIO BOARD 48.4W006.021.

This diode has no burnt marks or cracks so I'm assuming its open on the inside. Thanks again

[whaldsz]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

No voltage on pin 15 (S5_enable) and pin 16 (RSMRST) of SIO chip. I suppose to have voltage here when power button is pressed?

And also is it normal to have voltage present on L14 coil approximately 1.80v when there is no adapter or battery attached? This voltage slowly drops until it reaches 0 when I put meter on it. Tested this coil and its not shorted. Voltage also present on U5, R204 and C375 of battery circuit. Thanks again.

You need S5_ENABLE coming from SIO to have 3.3V and 5V ALW.

Since you don't have RSMRST# do one or more of the following:

1. Reflash the bios
2. Confirm that pin 93 of SIO is HIGH.
3. Confirm that you have 32.768Khz at X5.

About L14, don't worry about that for now. The charger IC should enable charging when the battery is inserted.

[lezsimply]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

Thanks for the info.

-0v on pin 93 (AC_IN) of SIO chip
-I'll visit my friend for him to flash the bios.
-Don't have scope for the crystal, that's one of my 5 wishlist on christmas
but I've got same working one to replace it.

I'll post results later thanks again bro!

[whaldsz]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

work on this one first - AC_IN#. it should be high. even if you reflash the bios, you will not get S5_ENABLE high if this is not fixed.

[whaldsz]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

In the image below how would I test this component circled in red if its open or not? I know its a diode but I can't seem to find datasheet for it.

Just curious because I only get 19v on one side unlike on some acer and hp netbooks diodes have voltage on both sides. The reason for asking is because dc jack has 2 pins for positive (19v) which separates along the way. The other is connected to this diode labeled D2. I don't have any diagram of the other board labeled DS2 LIO BOARD 48.4W006.021.

This diode has no burnt marks or cracks so I'm assuming its open on the inside. Thanks again

Your voltage reading is correct. You should only get 19v when positive probe and 0v on the cathode when you measure the voltage with respect to ground.

This is a protection mechanism for a scenario where you accidentally inverted the 19v input (-19v). It does nothing for normal operation but shorts the input when -19v is fed to the motherboard, preventing damage to critical components.

[lezsimply]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

Thanks! That's what I also read from other forums. I'm working on the SIO chip not getting power.

I guess this is my weakness. Its really hard for me to fix laptop which are dead especially when adapter and dc jack are ok. Still got 3 dead laptops here and I don't know if I can fix all of this before holiday comes

To be honest doing board repair on laptops started just this year. I decided to try a different level. I usually fix desktop computers which are more easier to fix. Maybe I just need to go on a training course for this. Thanks again! Need to get back to what I'm doing just took a break

[lezsimply]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

I'm a little bit confuse here

Source of AC_IN for SIO comes from C68 all the way from R48 and Q23. I've got 0 volts on C68 but 4.99 volts on R48. What voltage I must have in drain of Q23 transistor?

On Q23 gate I got 3.26v, is gate of Q23 connected to R240 which have 19v present?

And also regarding resistor R241 one end measures 19v and other measures 6.27v Is this right? Please check the image below. Thanks very much!

[whaldsz]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

Measure the pin voltages of U46. ACAV_IN should be low. With ACAV_IN high, it shorts pin 3 of Q23 to ground, thereby pulling the voltage of pin 3 - AC_IN# to 0v.

[lezsimply]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

So far these are voltages I measured on U46 MAX8731AE Battery IC

pin 22 DCIN 19.48v
pin 2 ACIN 2.24v
pin 11 VDD 3.3v
pin 26 VCC 5.34v
pin 13 ACOK (ACAV_IN) 3.26v
pin 21 LDO 5.37v

R40 to ad+ 19.48v while opposite gives 2.24v to C383 which goes to acin max8713ae
This resistor R40 is a 365kohm but meter says 57k only (Page 39)

[whaldsz]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

So far these are voltages I measured on U46 MAX8731AE Battery IC

pin 22 DCIN 19.48v
pin 2 ACIN 2.24v
pin 11 VDD 3.3v
pin 26 VCC 5.34v
pin 13 ACOK (ACAV_IN) 3.26v
pin 21 LDO 5.37v

R40 to ad+ 19.48v while opposite gives 2.24v to C383 which goes to acin max8713ae
This resistor R40 is a 365kohm but meter says 57k only (Page 39)

ACIN is normal. but ACOK is not. should be 0v. Try to replace this chip.

[Francisco.s]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

ACIN is normal. but ACOK is not. should be 0v. Try to replace this chip.

There will be an error somewhere with ACOK signal.....

[lezsimply]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

So possible fault is Max8731A IC? Just ordered it yesterday but I think it will arrive on Monday. Can't wait to put in on to see results.

I'm on the datasheet now. I want to clarify something regarding ACIN and ACOK. Something is not clear to me I will keep on understanding those statements. Thanks guys!

[Francisco.s]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

So possible fault is Max8731A IC? Just ordered it yesterday but I think it will arrive on Monday. Can't wait to put in on to see results.

I'm on the datasheet now. I want to clarify something regarding ACIN and ACOK. Something is not clear to me I will keep on understanding those statements. Thanks guys!

Post results when you have it.

[lezsimply]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

While still waiting for the replacement ic. Just wanted to ask you guys whats the meaning of the enclosed statement in the image below. Sorry still noob on those kind of stuff. Thanks!

[whaldsz]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

While still waiting for the replacement ic. Just wanted to ask you guys whats the meaning of the enclosed statement in the image below. Sorry still noob on those kind of stuff. Thanks!

I made a serious mistake in my previous posts, didn't see ACAV_IN is connected to resistors R235 and R236. My apologies.

Let us use your schematic to understand the statement from the datasheet, first the pin ACAV_IN is connected to a 5.4V voltage source through a voltage divider R235 & R236. For MAX8731A, REF pin is around 2V, so REF/2 would mean 1V.

There are two scenarios:

1. When AC is detected ( ACIN is around 2.3V which is greater than REF/2 or 1V)
2. AC is not detected, ACIN is less than 1V.


Behavior of ACAV_IN or ACOK Pin:

1. When AC is detected, ACAV_IN pin is like an open circuit with respect to ground or high resistance. Therefore, the voltage seen at ACAV_IN is equal to (5.4v x 15/(10+15)) = 3.24v . This phenomenon makes pin 2 & 3 of Q19 a short circuit because this 3.24v is fed to pin 1 of Q19. This makes the voltage at AC_IN# = 0v, AC_IN# is shorted to ground.

2. When AC is not detected, ACAV_IN is shorted to ground (see Figure 2 of the datasheet) or ACAV_IN is 0v. This makes pin 2 & 3 of Q19 an open circuit because there is no voltage at the gate or pin 1 of Q19. Therefore, AC_IN# = 3.3v.

[lezsimply]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

Thanks for a well explained situation One thing, I cannot find R235, R236 and Q19 on schematic what page is it? Maybe I'm just too tired, for 3 days I had only 8 hours of sleep I've got overflow of repairs this week. Need to finish before 25. Thanks again bro!

[whaldsz]

Re: Dell 1525 DS2 Intel Tps51120 faulty or not?

Thanks for a well explained situation One thing, I cannot find R235, R236 and Q19 on schematic what page is it? Maybe I'm just too tired, for 3 days I had only 8 hours of sleep I've got overflow of repairs this week. Need to finish before 25. Thanks again bro!

page 37 of your schematic diagram. Located upper left corner.