HP Victus 16 Hall Effect Sensor Failure and Solution

Usage: Can be quoted as long as credited; cannot be used commercially. If you have any questions or opinions, you can reach me at my email address gungozb@gmail.com.

WARNING: The hardware modifications in this documentation require SMD-level soldering skills, schematic reading competence, and electrical measurement knowledge. The responsibility for any possible hardware damage, data loss, or personal injury that may occur during the application of the information presented here belongs entirely to the individual. Any physical intervention will void your device’s manufacturer warranty. The device must absolutely be de-energized and the battery socket must be unplugged while performing all operations. Since the SMD component packages are small and the working area on the board is narrow, extreme caution must be exercised to avoid damaging other components. The live voltage measurements mentioned in this guide are the only exception and must be carried out with the precautions given at those steps.

I ACCEPT NO RESPONSIBILITY WHATSOEVER FOR THE CONSEQUENCES OF ANY INCORRECT OPERATIONS YOU PERFORM!

1. Introduction

This article covers the analysis and solution method of the hall effect sensor failure, which presents typical symptoms such as sudden system shutdown, black screen, hardware freeze, and screen flickering, mostly observed under high thermal load in HP Victus 16 series (especially s0 and r0 variants) laptops. The root cause of the failure is that the original hall effect sensor is actually thermally incompatible with the design, and a fuse located on the supply line suffers thermal degeneration due to a faulty thermal design. Details regarding why the original sensor experiences thermal instability due to this faulty design will be explained in the following sections. The problem occurs when the system assumes the lid is closed and turns off the keyboard and screen backlights, triggered falsely by the EC chip due to the hall effect sensor. Because the sensor circuit, operating unstably under thermal stress, constantly mis-triggers the EC, it results in random on/off switching and flickering of the screen and keyboard backlights.

The sources utilized throughout this documentation can be found in the references section at the end of the document. Two main solution methods are mentioned in the provided sources, and this documentation will focus on applying both solution methods together, detailing why both are necessary in the upcoming sections. I have personally applied the procedures explained in this documentation to my own computer; it hasn’t been very long since the repair, but I no longer experience any problems. I stress-tested the computer for long periods with thermal tests, and everything operates normally; I can confidently say the problem is solved.

2. Diagnosis

If the user’s keyboard backlight is off, turning it on will help to observe this problem better and realize that it is not solely a screen-related issue. Unfortunately, there is no software solution. I completely cleaned both internal and external graphics card drivers with DDU and performed a clean install, updated the BIOS, and besides these, I don’t think there will be a higher-level software solution anyway, so there’s no need to waste time reinstalling the OS. None of them worked. The problem persists even if “Do nothing” is selected when the lid is closed from the Windows power options. Since I still experienced symptoms like screen flickering and the screen and keyboard backlights turning on and off despite all these attempts, I became certain that my problem was a hall effect sensor failure.

The main cause of the failure is thermal degeneration and thermal instability. However, this thermal stress does not only affect the hall effect sensor; it also corrupts a fuse on the hall effect sensor supply line, causing thermal degeneration which manifests as an increase in impedance. The original sensor is a Toshiba TCS40DLR with the LA8 code, and the datasheet data regarding the operating conditions for the original sensor is available below.

The maximum operating temperature is at a very restrictive level for a gaming laptop. In fact, Toshiba included a statement regarding this situation in the datasheet:

As a result, no matter what hardware modification is performed, this sensor is not a suitable choice for this laptop design; replacing it with another sensor that has higher temperature tolerance is absolutely necessary. The fuse bypass operation on the supply line of the sensor, which I will mention shortly, will not be sufficient on its own; after some time, the original sensor will operate unstably due to thermal stress.

3. Solution

The hall effect sensor is not the only source of the problem; as I mentioned above, the corruption of a fuse on the supply line of this sensor is also a root cause. This corruption does not result in an open circuit like a classic fuse failure; it occurs as an impedance increase following thermal degradation, thereby causing instability in the supply line. To determine if this fuse has genuinely failed, a resistance measurement can be done if desired (it won’t give a definitive result without desoldering it from the circuit, but I couldn’t see a parallel resistor to this fuse, so it may provide an approximate result if the probes are held long enough) or a check in continuity mode can be performed. My resistance measurement on the circuit resulted in 260 ohms. This value may vary depending on thermal fatigue. I didn’t get a continuity beep during the continuity test; the multimeter still displayed 260 ohms. Based on my measurement results, the fuse has definitely lost its primary function and now acts as an impedance on the line. However, this impedance will vary according to the state of the failure, meaning the fuse’s impedance will progressively increase due to thermal stress.

The real problem is the collapse of the hall effect sensor supply line voltage due to this impedance increase. Looking at the references, modifications such as routing a trace from the IR sensor supply for the hall sensor supply line were executed for this reason, but these are unnecessary. In this article, bypassing this degraded fuse will be explained as a cleaner solution. I measured a 30mV drop on the fuse while the circuit was energized (caution is required here, faulty probe contact on the circuit can cause a short circuit); if the impedance of the fuse had been higher, this drop would be even greater, causing the sensor supply line voltage to collapse. The most crucial point is that due to this faulty fuse, since the operating current of the Allegro sensor I installed is higher, the line voltage will drop even further, and the new sensor will also operate unstably. Therefore, a simple sensor replacement will not be enough; bypassing the fuse is absolutely necessary to stabilize the supply line.

Bypassing a fuse might seem like a dangerous approach. The job of this fuse is to protect the 3V3 line if a short circuit occurs on the sensor board or on the FFC cable connecting it to the motherboard, so it is not a protection that should ever come into play unless there is physical damage on the sensor board (a crushed cable, a solder bridge, liquid contact and so on). Even in that case the protection is still provided, because the regulator circuits in the supply section have their own overcurrent protection for the 3V3 line. However, since the regulator’s protection threshold is in the ampere range, a partial short that stays below this threshold can heat up the cable and thin traces; anyone who wants to eliminate this risk completely can fit a new fuse of a suitable rating instead of bypassing it. It should also be noted that the short-circuit protection mentioned in the Allegro sensor’s datasheet belongs to the sensor’s output pin, it protects the output transistor and not the supply line; in other words, the safety of the bypass relies on the regulator’s protection, not on this one. Since a complete solution is presented in this article, I didn’t feel the need to address other symptoms and alternative solutions. If it is not possible for the user to apply the procedures explained here and they seek an easier workaround, a few simple solutions mentioned can be tried by thoroughly examining the links I provided in the references section.

I used the Allegro A1126 sensor as the new hall effect sensor. I preferred this component because I could source it quickly and easily; a suitable sensor from a different brand or model can also be chosen by comparing the datasheet data of the original sensor with the prospective one. The Allegro A1126 hall effect sensor is an automotive-grade component and is thermally much more durable than the original sensor. Plus, as I mentioned above, it has features such as a short-circuit protected output. The most significant difference from the Toshiba sensor is the way it draws current. The Toshiba sensor does not draw current continuously; as stated in its datasheet, its internal circuit draws current in periodic pulses, so the 1.2mA given for 3.3V is the peak value of these pulses and the average current is far below it. My measurements confirm this: with the original sensor installed I measured a 30mV drop across the fuse and 260 ohms for the fuse, which gives an average current of 30mV / 260Ω ≈ 115µA (if 1.2mA were drawn continuously, the drop would have been 312mV). The Allegro sensor, on the other hand, is a chopper-stabilized sensor that draws current continuously, and its datasheet gives a maximum supply current of 4mA. With the same faulty fuse, in the worst case there will be a 4mA × 260Ω ≈ 1.04V drop across the fuse, meaning only about 2.26V will reach the sensor, which is well below its minimum supply voltage of 3V. Looking at it the other way round, the 0.3V margin between 3.3V and 3V is only enough up to 0.3V / 260Ω ≈ 1.15mA with a 260 ohm fuse; the datasheet does not guarantee that the sensor stays below this current, and as the fuse’s resistance increases with thermal stress this limit will drop even further (the original sensor could tolerate the faulty fuse for a while because it works down to 2.3V, the Allegro sensor does not have this margin). Therefore, the new sensor cannot operate stably without bypassing the fuse.

The temperature will be much higher while the laptop is under load, but the datasheet data for the original Toshiba hall effect sensor under nominal conditions is as follows:

Table showing the 1.2mA requirement for 3.3V of the Toshiba sensor:

The datasheet data for the Allegro sensor is as follows:

Table showing the minimum supply voltage, maximum value of the current limit, and supply current for the operating state of the Allegro sensor:

Image containing the text about overcurrent protection in the description section of the Allegro sensor datasheet:

Table showing the operating temperature range for the Allegro sensor:

It can be seen that the minimum supply voltage for the Allegro sensor is 3V. For this reason, the sensor’s supply line must absolutely be stable; therefore, the broken fuse (or the one that will inevitably degrade over time due to thermal stress) on the supply line must definitely be bypassed (if the newly installed component lacks high-temperature tolerance, it will similarly suffer thermal degeneration) so that the line voltage never collapses (there is already a strict 0.3V margin for maximum voltage drop). Additionally, as stated in the datasheet description for the sensor, there is a 60mA current limit. This limit belongs to the sensor’s output current, meaning that if a short circuit occurs on the output line going to the EC, the sensor’s output will protect itself. As shown, the upper operating temperature limit of the Allegro sensor is 150°C, which is 65°C higher than the original sensor’s upper limit of 85°C.

The pins of the original sensor and the new sensor are completely compatible, meaning the old one can be removed and the new one can be directly soldered in its place; the Toshiba sensor comes in a SOT-23F package and the Allegro sensor in a SOT-23W package, and the two packages are compatible with each other.

Pinout illustration for the Toshiba sensor:

Pinout illustration for the Allegro sensor:

The steps in the HP maintenance guide can be followed to access the daughterboard where the sensor is located:

Image showing all the cables that need to be disconnected first to be able to remove the motherboard:

Image showing the removal of the motherboard:

Image showing the removal of the daughterboard where the hall sensor is located:

As can be seen, the entire motherboard needs to be removed from the chassis to access the board where the hall effect sensor is located. For all procedures up to this point, the HP maintenance and service guide document should be carefully reviewed. The link to the guide is provided in the references section.

Hall sensor board (IR sensor side) image:

Hall sensor board (Hall sensor side) image:

Images of the sensor board can be examined above; higher resolution versions can be accessed from the links provided below.

Close-up image of the Hall sensor board (Hall sensor side):

The Toshiba sensor can be removed using a hot air rework station or soldering iron, and the Allegro sensor can be directly installed:

Image showing the Hall sensor board (Hall sensor side) replaced with the A1126:

As seen, there are two capacitors in close proximity to the sensor; since their packages are extremely small, it will be difficult to resolder them if they are accidentally dislodged. Furthermore, if hot air is utilized, the JIR2 socket may melt or sustain damage from the heat. For this reason, prior to the procedure, the area surrounding the sensor and the vulnerable socket should be masked with kapton tape. After the replacement, one or two layers of kapton tape can be applied over the sensor for physical reinforcement. As an extra measure, a thin insulating block can also be built by placing teflon tape between the layers of kapton tape; I tried this, and the block conducts almost no heat from one side to the other. However, this block only reduces the heat reaching the sensor from above, it cannot stop the heat that reaches it through the copper traces and pins on the board. Since the Allegro sensor’s temperature tolerance is already high enough, it is not required for it; it can be considered as a simple extra protection for those who keep using the original sensor, or for the new fuse or 0 ohm resistor fitted in place of FU6 (if applied over FU6, make sure it does not prevent the heatsink from seating properly). The block must be kept thin, if it is too thick it bulges between the sensor board and the motherboard and puts pressure on the board. The work on the sensor board is now complete.

To perform the operation on the aforementioned fuse, the sensor board must be reinstalled, the motherboard must be remounted, and subsequently, the copper cooling pipes must be removed. The sensor can be visually inspected without removing the copper pipes, and necessary ohm, continuity, and voltage measurements can be taken, but removing the heatsinks is mandatory to physically work on the board. After removing the heatsink screws, it should be carefully lifted at a 90-degree angle, and the thermal putty should be left intact if it is still pliable (if it is dry and brittle, it needs replacement). Since the cooling block is detached, reapplying fresh thermal paste is mandatory, and when the copper pipes are reinstalled the screws must be tightened in the torque order.

The fuse is designated as FU6 and is located right next to the socket named JIR1, where the board housing the hall and IR sensor connects to the motherboard.

Close-up image showing the FU6 fuse:

Wide-angle image showing the FU6 fuse:

Extreme close-up image showing the FU6 fuse:

I couldn’t find any exact specification data regarding the original fuse; I presume a replacement fuse rated around 100-200 mA in a matching package could be installed, or perhaps a 0-ohm resistor in a suitable package. However, considering the persistent thermal stress, I don’t think replacing it is a logical long-term solution, which is why I removed the fuse entirely and bypassed it with a solder bridge.

Close-up image showing the removed state of the FU6 fuse:

After removing the component from its pads, I bypassed the FU6 fuse using a solder bridge, and upon checking with a multimeter (extreme caution must be exercised while the board is energized), I verified that the 3.3V line reached the pin on the socket flawlessly.

Image showing the FU6 fuse bypassed with a solder bridge:

This verification should also be performed while the board is de-energized by testing the continuity between the fuse pad closest to the socket and the pins of the socket to determine exactly which pin should carry the 3V3 voltage. Following all soldering operations, the structural integrity of the solder joints must be thoroughly verified with a continuity test.

4. References

1. Reddit: HP Victus 16 Hall Effect Sensor Megathread Author: RaguTom

2. BADCAPS: HP Victus 16 Hall Effect Sensor Problem Author: mitchw

3. Maintenance and Service Guide Victus by HP 16.1 inch

4. Toshiba TCS40DLR Datasheet

5. Allegro A1126 Datasheet

5. Additional Images

Click here for Google Drive Folder

Bugra