Diode replaced from a doner board, voltage now around 2044 but some times rised up till 20.7 than stabilized around 20.6. resoldered the 10ohm resistor in place and measured VCC... same identical situation as before... Could it be that the IC is struggling to manage the output of the second MOSFET, perhaps due to a varying demand for current from Vcc? It might be that, for some reason, it shuts down and then immediately attempts to restart, only to encounter the same conditions forcing it to vary its current draw again. This could create a sort of loop, which would then manifest as fluctuating current consumption and cause the measured Vcc voltage to vary continuously?
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With no power to the board, meter in resistance mode, what is the resistance to ground of pin # 28 = Vcc?
We are checking if perhaps the 1uf @ PC314 is shorted. That is, once yo mate the dual diode & PR312 (10 ohm) resistor, the voltage should still remain stable. This is based on the assumption that there are no shorts on PU301 and that PU301 is not defective. Regardless of the issues with other parts, the VCC leg of this circuit should be stable.
Can you also test PQ302 (if not done already)?
With meter in resistance mode, test:
source / drain
source / gate
gate / drain
pins. Each should be hundreds of k ohms or higher if the (battery) mosfet is ok.Comment
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with PR312 in place, negative probe on ground positive on vcc ..6.85Mohm, reversing probes 0.5Mohm. Without PR312 negative probe on ground 8.3Mohm, reverse 1.94Mohm
PC314 not shorted
PQ302 seems to be ok no low resistance in any probing combination.
No low impedance on any of the pin of PU301Comment
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Each mosfet resistance test should be hundreds of k ohms or higher - is this correct?Comment
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I removed PQ304 and measured VCC again... Perfectly stable! Could it be something related to the PQ304 load side? I wondered. The MOSFET has also been replaced with no luck. Without it, the IC seems to function properly, providing the correct gate voltage and showing a perfectly stable VCC.
Next, I tried removing both current sense resistors (PR335 and PR304), and, as expected, I got 19V_P2.
What's still driving me nuts is the 4.27V reading I get on the +19VB side...
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still measuring Mohm value on +19VB... Apparently no direct short on this rail but someting get weird when powerd up. Can we exclude problems on PU301 side? Injecting voltage on this rail without a short would it make any sense?Comment
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If the resistance is not low then voltage injection will not help. Voltage injection is helpful to smoke out shorted parts.Comment
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Yes, I agree. However, how can I determine what is happening at +19VB that prevents the charging circuitry, which seems to be functioning correctly, from delivering voltage to the rest of the board? If there is no short circuit, what should I check next? The only assumption I can make at this point is that the short might not be on the main rail. However, I haven't been able to identify any shorts on any of the coils.
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To further narrow down the issue, I selectively removed the jumpers connecting the main power rail to various sections of the circuit in order to identify the faulty section responsible for the malfunction, which causes the +19Vb power rail to shut down due to the primary power circuit entering protection mode. This method allowed me to pinpoint the jumper labeled PJ403, associated with the 3V3 generation circuit connected to the PU401.
However, no short circuit was detected at the output of the 3V3 generation circuit. This suggests that the issue might extend to other components or sections sharing the same power rail, making it more challenging to pinpoint the exact cause. How would you proceed from here?
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Measure the resistance to GND on +3VLP aka LDO?Comment
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the resistance value on +3VLP is 32Kohms measured on PC411 with red probe on ground, viceversa I don't get a fixed value.
Considering that PJ403 powers only the circuit of PU401, I decided to reconnect that jumper and open PJ401, which is instead related to +3VALWP. However, at that point, I once again lose the +19VB.Comment
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I have an HP 15-DY laptop in because the battery is not charging.
If I use a charged battery, the laptop powers on but the battery will not charge, however the orange charge light does turn on. The laptop loses power as soon as I disconnect the battery.
I've replaced the BQ247 chip with a known working one and I get the same issue and the same measurements.
Measurements are as follows:
BQ728 IC
VCC (Pin 20) => 19V
CMSRC (Pin 3) => 0.8V (This is a problem but I can't figure out what's causing the low voltage)
ACDRV (Pin... -
Hello from France
My daughter spill some water on her laptop... Lenovo Ideapad Gaming 3 15ACH6, and she doesn't seen anything wrong after just remove the water with towel.
Then, later the laptop won't start anymore.
I've made a basic troubleshoot with my own laptop (same series)
So, the computer battery is totaly out. With my battery, the computer works !
But, with PSU connected, the latptop detect the power.. the harware led white is on, the amber one too and on the screen there is a 'batt charging' message.
But... -
Hi all, I have a Asus TUF Gaming F16 (2024) FX607J motherboard with liquid damage. The oxide on the board was removed before giving it to me. This made it more difficult to repair. Also they did not give me the power supply.
When I connect the 20 volts with the bench power supply I get 4.3 volts on the main power line. If I remove the power sensing resistor I get 20 volts on one side (first 2 mosfets are ok) and 4.3 volts on the main power line (see photo). How is this possible?? I thought the 4.3 volts was coming from the battery mosfet so I unsoldered it and tested it. It is ok too. I... -
Hi people, i have an acer nitro 5 with motherboard model gh51m la-k861p , it came with the resistor pr103 blow up, i repaced that resistor, i check the coils plb2, pl301, pl501 and has no short to ground, i conect the charger and it doesnt power at all, i check pqb3 on pin 5 to 8 and its 19v, pin 1 to 4 its 0
so i repaced, pqb3, pqb4, and makes no change, still no acdrv, i replaced bq24781 and makes no change, still no acdrv, if someone can help pls, thanks, this are the schematic and boardview
[MOD EDIT] LINK to schematic & boardview -> https://www.badcaps.net/forum... -
Hello my precious masters;
Lenovo LOQ - LA-N221P Rev 1.0 I need the code/model number of the PU301 integrated circuit on this mb. The integrated circuit is burnt and cannot be read. Can you help me with this?
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