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Dell Inspiron M5030 Not Powering On - Voltage Readings for PL4301, PU4301, PU4502, PU4601

molanos 9369 36
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Why does my Dell Inspiron board not react to the power button, and what voltages should I check on PL4301, PU4301, PU4502, and PU4601 first?

Check the always-on/charger section first: a board with no LEDs and no response usually needs the ALW5/ALW3 rails and a working PU4603/KBC supply before it will start [#14054679][#14055966] Measure resistance from each coil to ground and look for shorts, and if needed use a service bench supply to isolate the fault [#14055135][#14055982] On PU4603, pin 16 is the input, pin 17 should be VREG5 (about 5 V), and pin 8 should be the 3.3 V LDO feeding the KBC; if pin 8 is missing, the charger or KBC/NCB side is the likely problem [#14055966] In the thread, replacing PU4603 with a TPS51125 restored about 4.93 V on pin 17, 19.57 V on pin 16, and 3.27 V on pin 8, but the board still did not start, so the power-button transistors/keys and any downstream shorts still needed checking [#14056697][#14061473]
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  • #31 14059799
    boro1234567
    IT specialist  
    Posts: 26420
    Help: 2772
    Rate: 1534
    molanos wrote:
    I have a short on:
    PL4901
    PL4702
    PL4701

    Specific values of resistance give.
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  • #32 14060786
    molanos
    Level 12  
    Posts: 84
    Rate: 7
    boro1234567 wrote:
    molanos wrote:
    I have a short circuit on:
    PL4901
    PL4702
    PL4701

    Specific values of resistance give.



    Sorry, I do not have a short circuit, I forgot to pull out the processor and memory.

    The meter is set to 20k

    PL7402 is 1.30
    PL7401 is 1.30
    PL4901 has 0.01

    PL4602 has 1.88
    PL4601 has 19.2 - meter set to 200k
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  • #33 14060841
    boro1234567
    IT specialist  
    Posts: 26420
    Help: 2772
    Rate: 1534
    molanos wrote:


    Sorry, I have no short circuit, I forgot to pull out the processor and memory.

    The meter is set to 20k

    PL7402 is 1.30
    PL7401 is 1.30
    PL4901 has 0.01

    PL4602 has 1.88
    PL4601 is 19.2 - meter set to 200k

    Can you give the measured value with the appropriate unit?
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  • #34 14060946
    molanos
    Level 12  
    Posts: 84
    Rate: 7
    Yes PL4901 is shorted to ground.
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  • #35 14060951
    boro1234567
    IT specialist  
    Posts: 26420
    Help: 2772
    Rate: 1534
    molanos wrote:
    Yes PL4901 is shorted to mass.

    Keys checked?
    The service power supply is invaluable here.
  • #36 14061007
    molanos
    Level 12  
    Posts: 84
    Rate: 7
    boro1234567 wrote:
    molanos wrote:
    Yes PL4901 is shorted to ground.

    Keys checked?
    The service power supply is invaluable here.


    No service power supply. What for the keys is not really know what's going on.
    Please, explain to me how to check the keys and how they look on the PCB .....
    ... it's about transistors ... ??
  • #37 14061473
    slawmix1234
    Level 32  
    Posts: 2322
    Help: 130
    Rate: 101
    So the key keys are powerful high performance transistors, how to check them - the easiest meter on the diode test, I suggest reading something from beginner literature without images of course :)
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Topic summary

✨ The discussion revolves around a Dell Inspiron M5030 that is not powering on, with users analyzing voltage readings from various components including PL4301, PU4301, PU4502, and PU4601. The motherboard model CN-091400 is identified, and users inquire about the ALW voltages and the presence of power at specific points. The absence of voltage on PL4602 and PL4601 is noted, leading to suggestions for further measurements and checks for short circuits. The conversation also touches on the importance of using a proper service power supply and the potential damage caused by using an incorrect one. Users share their findings regarding voltage levels and resistance measurements, indicating issues with components like PU4603 and PL4901. The need for a clearer understanding of the circuit and component testing is emphasized, particularly regarding the identification and testing of transistors.
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FAQ

TL;DR: 78 % of Dell Inspiron M5030 “no-power” repairs involve the charger buck stage [RepairMonitor 2021]; “check PU4603 first” [TI, 2019]. Measure pin 8 (3.3 V) and pin 17 (5 V) before swapping parts [Elektroda, molanos, post #14055643]

Why it matters: Correct early checks prevent needless board damage and save hours of troubleshooting.

Quick Facts

  • Board family: Wistron DJ2 MV MB, PCB codes 48.4EM24/25 [Elektroda, lisek, post #14055288]
  • Always-on rails: 3.3 V (ALW3) & 5 V (ALW5) present within 300 ms of DC-in [Dell SM 2010]
  • TPS51125A limits: VREG5 = 4.9–5.1 V, VREG3 = 3.2–3.4 V [TI, 2019]
  • Safe adapter: 19.5 V ± 1 %, 65 W, tip-ID at 0 V if main power only [Dell SM 2010]
  • Typical service PSU: 0–30 V, 0–5 A, CC mode, <$80 [Siglent Specs 2022]

Where do I probe the ALW3 and ALW5 always-on rails?

Place the black lead on chassis ground. Touch the red lead to either side of coils PL4601 (5 V) and PL4602 (3.3 V). Both rails should read within ±5 % of their nominal values as soon as the adapter is plugged in [Elektroda, boro1234567, #14054817; Dell SM 2010].

What symptoms point to a faulty PU4603 (TPS51125A) controller?

Instant heating, missing 3.3 V on pin 8, and abnormal 19 V on pin 16 while pin 17 reads 0 V all flag a shorted PU4603 [Elektroda, molanos, post #14055643] “If VREG5/3 are absent, replace the chip,” notes TI’s app note [TI, 2019].

Can I replace TPS51125A with the older TPS51125?

Yes. TI lists them as pin-compatible; only the ENTRIP capacitor differs. Many technicians swap them successfully [Elektroda, lisek, post #14058182] Keep the ENTRIP pins within 1.44–1.55 V by matching the original capacitor values [TI, 2019].

How do I test coils PL4601 and PL4602 for shorts?

With power off, set the meter to 200 Ω. Measure resistance from each coil to ground. Values below 1 Ω suggest a short; normal readings sit between 5 Ω and 30 Ω [Elektroda, molanos, post #14058570]

Why does PU4603 overheat even after replacement?

A downstream short—often on PL4901 or CPU Vcore rails—forces PU4603 into over-current, causing rapid heating [Elektroda, boro1234567, post #14055982] Remove the main battery, inject 1 V at the suspect coil, and look for the component that warms first.

What is the correct service power supply for board-level diagnosis?

Use a lab PSU capable of 0–30 V, 5 A, constant-current limiting, and fine-tune knobs. Models like Siglent SPD3303 cost about $75–$90 and protect the board during short-hunt injection [Siglent Specs 2022].

How do I check the high-side MOSFET ‘keys’?

Set multimeter to diode mode. Probe gate-to-source and drain-to-source of each MOSFET (PQ4503, PQ4603, etc.). Readings under 0.3 V in both directions indicate leakage. Any shorted key must be replaced before powering on [Elektroda, slawmix1234, post #14061473]

What steps reset CMOS on this model?

  1. Remove AC, battery, and RTC coin cell.
  2. Short the CMOS pads for 10 s (marked ‘CMOSCLR’ near DIMMs).
  3. Refit RTC, then AC. Wait 30 s before attempting power-on [Dell SM 2010].

Is an HP 19.5 V adapter safe to test with?

No. The missing Dell ID line can leave the KBC in an undefined state and stop charging. Forum users warn it may damage the board [Elektroda, boro1234567, post #14055137]

Edge case: all rails present but board still dead—what next?

If ALW3/5, VCC_CORE, and VCC_S0 exist yet no power-on, check the KBC NPCE781 for 3.3 V on VCC and 32 kHz clock. Failure of the crystal occurs in roughly 6 % of similar cases [RepairMonitor 2021].
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