Hello, Lenovo Thinkpad E14 Gen.2 Type 20TA, GE4B0/GE5/B0 NM-D011 Rev. 1.0 board. Arrived in the following state: the device is always on and goes in a cycle: the "on" LED lights up, goes out after a few seconds and lights up again, cannot be turned off with the button. Inspection of the board is ok. The charger switches from 5V to 20V. I read that it seems to be a typical problem: the input MOSFETs QB5, QB6 do not open enough and get very hot due to the fact that TPS65994ADYBGR does not supply 28V to the gates. In my case, there were 21.4V on the QB5 gate, 28V on the QB6 gate, but the input MOSFETs do not heat up. The board is leaking, it seems to be approximately in the TPS area. The type-c jack is ok. The TPS strapping is ok. I changed the TPS (took from 2 sources), changed the input MOSFETs, no changes. The voltage of 21.4 V is not constant, but has a sawtooth shape, as if it is trying to reach 28 V and drops to 20 V. Consumption is 4-5 mA. Voltage and resistance on the TPS are ok, there is exchange on CC1 / CC2. I removed the capacitors that could theoretically affect (CB74, 75, 81) and the DB18 diode - no changes. Please tell me what else to look at, what could be leaking, are there really 3 TPS and all of them are defective? Thank you
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For each mosfet in the power path, test the resistance with no power to the board.
Measure:
source / drain
drain / gate
gate / drain
Post each measurement. Each should be hundreds of k ohms or higher else the mosfet may be defective. Test QB5 & QB6 for now.
The gate voltage on an N-channel mosfet must be boosted to a higher value than what is being passed between source / drain pins to enable. If you see 28v on QB6, I can only assume that QB5 should be similar unless QB5 is defective. -
Thank you.
Measured:
QB5
source / drain 1,08kohm
drain / gate 3mohm
gate / drain infinity
QB6
source / drain 1,08kohm
drain / gate 3,1mohm
gate / drain infinityComment
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The source / drain on each is too low. Flux and remove the mosfet(s). Test them again when they are on your workbench. Both may be defective.Comment
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Thank you, you have right, one of them (was new !!!) was defective, replaced both, now I have 28v at both gates, power consumption 8-12mAComment
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I think you are referencing QB5 & QB6 = AON7466 N-channel mosfets?,Q85 Drain 4,5v source 4,5v
Q86 Drain 4,5 v ssource 0,4 v
Datasheet:
https://www.aosmd.com/sites/default/...ts/AON7466.pdf
Being N-channel, the gate voltage must be higher than the voltage being passed between source / drain pins to enable this solid state switch.
What is the voltage to ground on the GATE pin # 4 of QB5? QB6?
Remove all power. Meter in resistance mode. Measure the resistance to ground of the SOURCE pins (1-2-3) - pick any of these pins. We are testing if there is a shorted part on the main power rail which may be causing this mosfet to remain disabled. Driven by the TBTA_GATE_VSYS signal.
Also, what is the source of UB7? Was it from a donor board or a vendor? Not sure at this time if the chip needs to be pre-flashed to use as this is the PD controller for the logic board so there is a need for firmware. Perhaps the firmware is injected by an outside host on the board or local flash IC or even the main BIOS.Comment
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The drain pin measurements do not make sense. The Vin is ~5v from the USB Type C power adapter so the most you should see is ~5v on the drain pins. Can you confirm the meter you are using is with fresh batteries?
Remove all power. Meter in resistance mode.
Measure the resistance across the mosfet pins:
source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)
Post each measurement. Test both dcin mosfets.Comment
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Q85 source, drane 7,15M OHMThe drain pin measurements do not make sense. The Vin is ~5v from the USB Type C power adapter so the most you should see is ~5v on the drain pins. Can you confirm the meter you are using is with fresh batteries?
Remove all power. Meter in resistance mode.
Measure the resistance across the mosfet pins:
source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)
Post each measurement. Test both dcin mosfets.
source gate 9,20M OHM
gate drain infinity
Q86 source, drane 7,15M OHM
source gate 9,05M OHM
gate drain infinity
When I connect the MOSFET Q86 to a wire it works but the battery must be connected when I remove the battery the device stops workingComment
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The mosfets do not look to be shorted but are not enabled under normal wiring.
?? Provide more details. Which wire? Which pin? Also the mosfets are QB6 - right? Not Q86. Q86 is not showing in my schematic.When I connect the MOSFET Q86 to a wire it works
Also, with the 'wire connection' - can the power adapter power the logic board or do you still need the battery? The battery cannot power the board unless you connect this bypass wire?Comment
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Measure the voltage again on the drain pins of these mosfets. Red meter probe on drain pin (5-6-7-8); black to ground. This voltage should be the Vin from the USB-C Vbus pin.Comment
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Hi everyone,
This is my first post so I'm hoping to get some help on this awesome forum. As a preface, I'm an amateur at electronics, especially troubleshooting complicated devices like laptops. However, I'm trying to develop a skill for it so I can learn how these devices work and how to repair them without continuing the wasteful tradition of throwing them away and buying new. 🤮
I've had a Lenovo Ideapad 5 14ITL05 for a few years now, with motherboard LA-K321P. I would never leave it plugged in unless I was using it, and always turned it off after I was done, but last week... -
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Hello guys,
I have a shorted MOSFET K8A60DA with the following characteristics:
Type Designator: TK8A60DA
Marking Code: K8A60DA
Type of Transistor: MOSFET
Type of Control Channel: N -Channel
Maximum Power Dissipation (Pd): 45 W
Maximum Drain-Source Voltage |Vds|: 600 V
Maximum Gate-Source Voltage |Vgs|: 30 V
Maximum Gate-Threshold Voltage |Vgs(th)|: 4 V
Maximum Drain Current |Id|: 7.5 A
Maximum Junction Temperature (Tj): 150 °C
Total Gate Charge (Qg): 20 nC
Rise Time (tr): 25 nS
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Hi there,
It seems no schematic or boardview is available for Lenovo LOQ 15ARP9.
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Top markings:
16 UUB
3A0601
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Hello everyone,
I'm working on repairing a Music Store Professional GO! SUB 18A bass subwoofer, and I need some help troubleshooting an issue with the power amplifier board. The board uses an IR2153 driver and originally had two SLW20N50C MOSFETs. Unfortunately, these MOSFETs burned out. I replaced them with two TK20J60W MOSFETs; however, these also failed almost immediately.
Here are some details:- SLW20N50C (original):
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- Typical RDS(ON): 0.21 Ω
- Continuous Drain Current: 20 A at 25°C (13 A at 100°C)
- Pulsed Drain Current: 80 A
- Avalanche
- SLW20N50C (original):
Comment