Two weeks ago, I had an Asus X555 that had no backlight when on battery. But it had steady backlight when on Charger. Then, I replaced the coil with a good one (100uH) from another screen. Then, the problem got fixed meaning that it had steady backlight when on battery.
However, the customer discovered that the backlight fluctuates when it is on battery and the battery charging level is under 50%.
What component does cause this problem?
What should I do now to fix it? Any similar experience?
caspian
Badcaps Legend
Last Activity: Yesterday, 03:32 AM
Joined: 10-03-2015
Location: Mainboard
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ok, so the zener diodes are fine.
Thanks @[B][URL="https://www.badcaps.net/member/66093-eccerr0r"]eccerr0r[/URL][/B]ok, so the zener diodes are fine.
Thanks @[B][URL="https://www.badcaps.net/member/66093-eccerr0r"]eccerr0r[/URL][/B]ok, so the zener diodes are fine.
Thanks @[B][URL="https://www.badcaps.net/member/66093-eccerr0r"]eccerr0r[/URL][/B]Leave a comment:
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there is no visible sign of damage or burning on the zener diodes and the board.
I tested the Zener diodes on board using the diode mode of multimeter. however, I do not know why my multimeter struggles to apply voltage on some of the zener diodes. On one direction, it shows infinite resistance. but on the other direction, sometime it shows 0.6v and sometimes it shows infinite resistance.
I used to use this power supply for voltage injection on laptop mainboards. I do now know why Q1 and Q2 got shorted.Last edited by caspian; 05-26-2025, 08:30 PM.Leave a comment:
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What Zener Diodes on a Linear Power Supply
Dear members,
I have a linear variable power supply with unknown brand name that I used for voltage injection.
Then it failed. I discovered that its transistors (Q1 and Q2) are shorted.
In addition, I discovered that its zener diodes are defective.
I can replace the burned transistors.
But I do not know the model of the zener diodes. the model number is not marked on the zener diodes.
Therefore, I cannot replace the zener diodes.
I do not want to test the zener diodes in a test circuit to discover their model or value.
no schematics are available...Last edited by caspian; 05-26-2025, 12:54 PM. -
I fixed the problem and now the colors are correct. The problem was bridge between the soldered pins of the resistor arrays....Leave a comment:
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This week, I have received a Dell n5010 and I have converted it into Intel Graphics.
After conversion, it gives picture , but the colors are different.
For example, at boot time, the background of the screen should be black and the text should be white, similar to the DOS environment. However, the background is red and the text is white in this laptop.
The other colors are different in Windows too.
I have inspected all the soldered pins and the conversion quality seems good.
the VGA port is not soldered and does not work.
After conversion, the...Leave a comment:
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To convert Asus x550LD rev.2 Dis to uma, only one resistor (marked in the photo) needs to change as below:
1. Disconnect Pin2 of that resister from its underneath pad.
2. Rotate that resistor such that Pin1 stays on its underneath pad and Pin2 connects to GND using a wire....Last edited by caspian; 09-21-2024, 10:50 AM.Leave a comment:
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OK, thank you
Your answer makes sense according to the symptoms that I observed....Leave a comment:
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the extra current is taken by pure mainboard without battery, screen, and other peripherals connected.
However, if I connect battery or peripherals, the drawn current is increased.
HWInfo shows that CPU is taking between 1A to 8A of current. with a typical current of 4A.
The maximum current is taken when Windows is loading.
I do not know what takes this extra current.
Leave a comment:
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Asus K555U taking extra current
Dear Members,
This laptop used to work with a 19v 3.4A adapter.
After 4 years of using it, now, the adapter's output voltage drops to 17v when windows loads up. Then the laptop suddenly turns off.
Today, I have connected a 19.8v 4.5A adapter to this laptop. Then the adapter's output voltage dropped to 19.4v but the laptop worked fine.
In addition, I noticed that the cpu power coils get warm to about 50'C but the mosfets are cool.
All the voltage rails on the mainboard are fine without any reduction except for the 19v rail. All the ICs and coils on the mainboard are... -
How can I modify An EC firmware?
Dear members,
I have an HP Elitebook 2540P laptop with mainboard: LA-5251P REV 1.0
It has a SIO with model: SMSC KBC1098
I think both the EC firmware and the main Bios reside in a single Bios chip.
Problem: KBC1098 is partially defective so that it does not generate ADP_En at Pin 75 and generates 8 amber blinks on the charging LED, indicating some wrong input.
Idea: Now I need to modify the EC firmware so that KBC1098 ignores the wrong input conditions and always generates a high ADP_En and does not enter a failure state.
Is it possible...Last edited by caspian; 05-21-2024, 02:03 PM. -
Is KT808AM compatible to 2SD867 ?
Dear members,
I have a linear Desk variable power supply that has an old Russian Transistor with model KT808AM. It cannot be found any more.
Is it right if I replace KT808AM by 2SD867 ?
Are these two transistors fully compatible according to their specifications and properties?
RegardsLast edited by caspian; 12-30-2023, 10:47 PM. -
Re: *Use Full MOST COMMON I.C FOR LAPTOP YOU SHOULD HAVE IN STOCK*
In the past, I had prepared a list of very popular common ICs for Laptops belonging to 2012-2014. Even though those laptops are quite old now, I print that list here, in case anyone needs it:
BQ24735RGRR_QFN20_3P5X3P5
BQ24737RGRR_VQFN20_3P5X3P5
BQ24725ARGRR_QFN20_3P5X3P5
SY8208BQNC_QFN10_3X3
SY8208CQNC_QFN10_3X3
SY8208DQNC_QFN10_3X3
RT8205LZQW(2)_WQFN24_4X4
RT8207MZQW_WQFN20_3X3
ISL95813HRZ-T_QFN20_3X4
APL5930KAI-TRG_SO8
ISL95833HRTZ-T_TQFN32...Last edited by caspian; 07-31-2022, 04:47 AM.Leave a comment:
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Re: Lenovo CE570 NM-A831 Rev 3.0, acpir in windows 10 setup
In addition, check this out:
[url]https://www.badcaps.net/forum/showthread.php?t=108349[/url]Re: Lenovo CE570 NM-A831 Rev 3.0, ac...t=108349[/url]Leave a comment:
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Re: asus gl502vsk no +vccore
Probably, the CPU and PCH are fine and the problem is somewhere in the CPU VRM circuit.Leave a comment:
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Re: Acer 5750G P5WE0 LA-6901P images only on external screen
Are the resistance relative to GND?
It is strange that both the pads are shorted.Leave a comment:
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Re: Acer images only on external screen
first remove R1 and measure resistance on each pad of it.
Moving R1 to R3 probably has no danger and probably does not solve the problem.
Does this laptop have a dedicated GPU chip?Leave a comment:
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Re: acer 5738g bios
If anyone has more Bios dumps for this mainboard, please upload it:
Acer 5738
Mainboard model:
jv50-mv ddr3 m92 mb
48.4cg08.011Leave a comment:
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Re: acer 5738g bios
I have another bios dump for this laptop but it does not work in my laptop. However, it is probably good....Last edited by caspian; 07-25-2022, 08:53 PM.Leave a comment:
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Re: Acer 5738 SIO replacement
I tried two different ICs, W25Q16BVSIG and MX25L1606 with a known good dump, but they all resulted in turning on but no display.
The original Bios IC was MX25L1605D.Last edited by caspian; 07-25-2022, 11:02 AM.Leave a comment:
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