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Lenovo Z50-70 ACLUA/ACLUB NM-A273 Dead Board: Voltage Issues, PD304 Diode, PQ301 Replacement

janko23 9816 17
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What voltage should be present after the PD304 diode on a Lenovo Z50-70 NM-A273 motherboard, and what should I check if the board still has no fan or display?

The voltage behind PD304 is not a fixed value; it depends on the adapter-ID/power-detection circuit, and if the board starts and the battery charges, that line is considered correct [#16843172] Do not inject 1.4 V into that node, and instead check the basic rails and detection path: +3VLP/+3VL from the 3 V/5 V converters, the adapter-ID signal, PQ995, and PR336 [#16847434][#16847773] Also verify the low resistance of the CPU and integrated-graphics power coils, because a short on those rails can keep the board dead [#16843172] Another hint from the thread is to inspect the PQ302/PQ301 control chain from the charger/BQ24737 side and confirm ACOK/BQ24737_VDD, since PD304 is tied into that control path [#16845381] The original poster later found the fault involved PQ301, the KBC, and the BIOS, and traced the PD304 line to the KBC through PR322 [#16855812]
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  • #1 16841592
    janko23
    Level 14  
    Posts: 320
    Help: 1
    Rate: 12
    Lenovo Z50-70 ACLUA / ACLUB NM-A273
    Laptop drove up dead. The voltage on the center pin of the 1.3V power socket. The voltage jumps 0.20V-1.29V behind the PD304 diode. Damaged PQ301, after replacing 4407A, the board started responding to the switch. So after pressing power, the diode lights up, after plugging in the battery, the charging diode flashes. The battery is charged with the voltage of about 14.8V, after removing the battery it is 1.9V. Unfortunately, only that much, the fan does not move, the image is missing etc. PQ302 4n -5.2V, the rest 1,2,3,5,6,7,8-20V. Voltage on UC3 (BIOS) -3.3V.
    The voltages appear on only three coils, PL302-1.9V PL304-5.1V PL303-3.3V. At rest it is 0V.
    The converter BQ737 substituted with BQ727 I had - no changes.
    What voltage should be behind the PD304 diode? . I will be grateful for any help.
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  • #2 16842671
    Dydelmax
    Level 39  
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    Hello.
    Enter the current consumption of the board with and without batteries before and after pressing Power.
    Did you check the BIOS?
    Do you have a schematic for this album?
    best regards
  • #3 16843038
    lisek
    Service technician RTV  
    Posts: 39712
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    The subject of this Link will help you find MS and explain some things.
    * there are only 9 topics about this MB
  • #4 16843172
    sk1977
    IT specialist  
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    janko23 wrote:
    What voltage should be behind the PD304 diode?
    - depends on the power of the power supply - it identifies the power of the power supply. If the board starts and the battery is charging - the voltage is correct.
    Also, do not look for a problem with the charger chip. Check that you do not have low resistance on the converter coils - in particular the CPU power supply and integrated graphics.
    Helpful post? Buy me a coffee.
  • #5 16843497
    janko23
    Level 14  
    Posts: 320
    Help: 1
    Rate: 12
    Bios pre-programmed, no schematic.
    The PL705 on the coil is only 13 Ohm. What voltage should be behind the PD304 diode? Thanks for the help in advance. best regards
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  • #6 16843891
    adamadi33
    Level 43  
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    Is PU 401 there, do you have + 3VLP or + 3VL?
  • #7 16845124
    janko23
    Level 14  
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    I cannot locate PU401
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  • #8 16845217
    adamadi33
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    Well, you have 3V / 5V converters on two SY8206BQNC systems.
    Lenovo Z50-70 ACLUA/ACLUB NM-A273 Dead Board: Voltage Issues, PD304 Diode, PQ301 Replacement
  • #9 16845381
    lisek
    Service technician RTV  
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    If it doesn't help anymore?
    Remember that (PQ302) P-ch and with him N-ch (PQ301)

    Lenovo Z50-70 ACLUA/ACLUB NM-A273 Dead Board: Voltage Issues, PD304 Diode, PQ301 Replacement Lenovo Z50-70 ACLUA/ACLUB NM-A273 Dead Board: Voltage Issues, PD304 Diode, PQ301 Replacement
    Lenovo Z50-70 ACLUA/ACLUB NM-A273 Dead Board: Voltage Issues, PD304 Diode, PQ301 Replacement Lenovo Z50-70 ACLUA/ACLUB NM-A273 Dead Board: Voltage Issues, PD304 Diode, PQ301 Replacement

    BQ should give a signal for PQ990B> this one should open PQ307B ...> this one opens PQ301 and PQ302.
    See what about the BQ24737_VDD?
    ACOK signal active.
    In the datasheet it is described as #, which is if 0? that's ok.

    ps
    These PD304 or AZ-5425-01f
    * identical in Compal_nm-a181, only numbering of transistors PQ312a / PQ312b

    Lenovo Z50-70 ACLUA/ACLUB NM-A273 Dead Board: Voltage Issues, PD304 Diode, PQ301 Replacement

    No LED> from this forum Link_ problem
    Availability Link_ about PLN 29 and datasheet in app.
    Attachments:
    • AZ5425-01F_Datasheet.pdf (190.82 KB) You must be logged in to download this attachment.
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  • #10 16845767
    adamadi33
    Level 43  
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    The diagram is not exactly like this board, but similar.
  • #11 16845852
    lisek
    Service technician RTV  
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    The 4th time is with
    Lenovo Z50-70 ACLUA/ACLUB NM-A273 Dead Board: Voltage Issues, PD304 Diode, PQ301 Replacement

    System PU904 (SY8206BQ) / PU905 (SY8208CQ QFN-10) i.e. 3.3V / 5V

    Lenovo Z50-70 ACLUA/ACLUB NM-A273 Dead Board: Voltage Issues, PD304 Diode, PQ301 Replacement
  • #12 16847166
    janko23
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    Both circuits produce a voltage of 3.3V and 5V. At the moment I have 0V behind the PD304 diode. Can I try to give these 1.4V from the middle pin of the socket?
  • #13 16847434
    sk1977
    IT specialist  
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    janko23 wrote:
    Can I try to give these 1.4V from the middle pin of the socket
    - no. Unless you want to introduce another bug.

    Check the basics - voltage on:
    ADAPTER_ID_ON # - for n. 84 NCBs.
    on all PQ995 feet
    BQ - voltage on n. 5

    PR336 - in case of problems with identifying the power supply, you can temporarily solder it.

    Measurement without batteries, only power supply - original, functional, with adequate power or service power supply with a properly prepared plug.

    Enter the hob's current draw before pressing the switch and after pressing it.
    Helpful post? Buy me a coffee.
  • #14 16847568
    lisek
    Service technician RTV  
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    You can give about 1.2V per pin from an external power supply. ADAPTER_ID / power supply on the board / + of course + 19V
    Should take off
  • #15 16847773
    adamadi33
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    Check this 3V regulator there are two such 3V and 5V.
    On the 3V system, you should have + 3VLP or + 3VL and check the resistances on this pin.
    There is pin 5 of the LDO on the system, i.e. +3 VLP.
    If there is no LDO there is a problem.
    You didn't need to replace the Charger chip.
    If you want to get help, answer the questions.
    Provide voltage from the regulator 3 V from 1 pin to 6 pin?
    Lenovo
    65 W, 20 V power supply:
    285 ohms from ID to GND.
    90 W, 20 V power supply:
    548 ohms from ID to GND.
  • #16 16847853
    sk1977
    IT specialist  
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    adamadi33 wrote:
    Check this 3V regulator there are two such 3V and 5V etc.

    Yet:
    janko23 wrote:
    PL304-5.1V PL303-3.3V


    lisek wrote:
    You can give about 1.2V per pin from an external power supply. ADAPTER_ID
    - for what?
    If there is no this voltage and there is EC_ON as evidenced by + 3VALW, then either the resistance in this circuit is low, or the KBC does not work properly, or the PQ995 or small items are damaged (assuming that the power supply, power supply socket is OK).

    You can
    sk1977 wrote:
    PR336 - in case of problems with identifying the power supply, you can temporarily solder it.
    - which will omit PQ995 and give a starting point for further actions.

    The author has not yet provided basic information with which to start - e.g. if the current consumed by the board is around 20mA - the KBC is damaged in 99% and there is no point in looking for other reasons.
    Helpful post? Buy me a coffee.
  • #17 16848599
    lisek
    Service technician RTV  
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    There at the damage. PD304. (Then this diode, as a damaged one, is a resistor of approx. 5/70 ohm in both sides, this can be measured after hitting the circuit) usually it falls on KBC (there is a small hole in the housing).
    * Measure the whole track from pin to kbc, will you eliminate other broken pieces?
  • #18 16855812
    janko23
    Level 14  
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    Hello, unfortunately after replacing the NCB (programmed). Bios rewritten. After switching on, the power LED went on, the battery LED blinked 5 times, both went out and then turned on again blinking from the battery 5 times. After a few such runs, both went out, and unfortunately the power does not light up anymore.
    The resistances of the keys without power supply with RAM, relative to mass. Other measurements of the battery contacts 1.9V, bios 3.3V, power 3.3V, rtc- 2.8V, short to ground behind the PD304 diode. Resistance from the middle pin to the pin behind PD304- 827 Ohm.

    PL307 -278Ohm
    PL701 - 152Ohm
    PL302 - 0.35MOhm (result after 30sec of measurement)
    PL705 - 12 Ohm
    PL706 - 12 Ohm
    PL9 - 253 Ohm
    PL304 - 75 kOhm (as PL302)
    PL303 - 368 Ohm
    PL302 -0.35 MOhm (result after 30 seconds of measurement)

    NCBs:
    21-0.02V
    26-3.34V
    72-1.43V
    86-3.34V
    93-3.34V
    111-3.34V
    124-0V
    128-3.34V

    The voltage from the pd304 diode goes to the n72 KBC, through the PR322 resistor, unfortunately I can't locate it.


    The problem was PQ301, KBC, BIOS. At the end, I messed up a bit myself, rearranging the general cargo to KBC. Thank you for your help. best regards
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Topic summary

✨ The discussion revolves around troubleshooting a dead Lenovo Z50-70 ACLUA/ACLUB NM-A273 laptop board, focusing on voltage issues related to the PD304 diode and the PQ301 component. The user reports fluctuating voltage readings at the power socket and behind the PD304 diode, along with a non-responsive fan and display. Various responses suggest checking current consumption, verifying BIOS functionality, and examining the power supply and converter coils. The importance of measuring voltages at specific points, such as the 3V and 5V regulators, is emphasized. The user also mentions replacing components like PQ301 and the BQ737 chip without resolving the issue. Further troubleshooting steps include checking resistances and ensuring proper voltage levels across critical components.
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FAQ

TL;DR: If idle current is ~20 mA, "the KBC is damaged in 99%"; start by checking PD304, ADAPTER_ID, and 3.3/5 V rails. [Elektroda, sk1977, post #16847853]

Why it matters: This FAQ helps bench techs quickly revive Lenovo Z50-70 NM-A273 boards that power but don’t POST, saving diagnosis time.

Quick Facts

What does the voltage behind PD304 tell me on NM-A273?

It encodes the power-supply identification. The KBC reads this level to accept the adapter. If the board starts and the battery charges, that voltage is considered correct. Low resistance on CPU or iGPU rails can still block POST, so check those coils too. “It identifies the power of the power supply.” [Elektroda, sk1977, post #16843172]

What are the correct Lenovo adapter ID resistances for this model?

Typical values measured from the center ID pin to ground: about 285 Ω for 65 W, and about 548 Ω for 90 W Lenovo 20 V adapters. If your reading is far off, the KBC may not authenticate the adapter and the board will not sequence. [Elektroda, adamadi33, post #16847773]

Is it safe to inject ~1.4 V into the center ID pin to test?

Do not feed 1.4 V into the ID pin. That risks creating a second fault. Instead, log current draw, confirm ADAPTER_ID_ON#, and check the PQ995 path and PR336 option. “Unless you want to introduce another bug.” [Elektroda, sk1977, post #16847434]

Which power rails must be present before pressing Power?

Confirm the always-on 3.3 VALW and 5 V rails from the SY8206/SY8208 regulator pair (PU904/PU905). Lack of these rails means the EC/KBC will not assert EC_ON and nothing else will sequence. Inspect those converters first. [Elektroda, lisek, post #16845852]

How do I interpret very low idle current on bench supply?

If the board draws around 20 mA at idle, suspect a failed KBC. In the cited case, such current indicated KBC damage with very high likelihood. Replace or reprogram the controller only after ruling out shorts on the ID line and PD304. [Elektroda, sk1977, post #16847853]

How is power passed through PQ301 and PQ302 during adapter insert?

The charger IC asserts control so PQ990B opens PQ307B, which then drives PQ301 and PQ302 to pass 19 V. Verify BQ24737 VDD and that ACOK# is active. Faults in this chain stop system rails from rising even with a good adapter. [Elektroda, lisek, post #16845381]

What is the KBC and how does PD304 failure affect it?

The KBC (keyboard controller/EC) sequences power and reads the adapter ID. A shorted PD304 can present low resistance both ways on the ID line and often takes out the KBC, sometimes leaving a visible hole. Inspect and replace as needed. [Elektroda, lisek, post #16848599]

How do I test for a PD304 short on the bench?

With power removed, measure resistance across PD304 in both directions. A failed part often reads low in both polarities. Then buzz from the jack’s center pin through PR322 to KBC pin N72 to find other damaged parts on the ID path. [Elektroda, janko23, post #16855812]

What battery voltage should I see during charging on this platform?

Around 14.8 V during charge is typical for the Z50‑70 pack. After removing the battery, a measurement of about 1.9 V reflects board-side sensing and not pack voltage, which is normal for this scenario. [Elektroda, janko23, post #16841592]

Where do I find the 3VLP/+3VL rail and what generates it?

The +3 VLP (LDO) and the 3.3 V rail originate in the 3.3 V SY8206BQNC regulator. Check pin 5 for the LDO output. Absence of LDO indicates a regulator-side fault rather than a charger issue. [Elektroda, adamadi33, post #16847773]

Can I bypass adapter identification to continue diagnostics?

Yes. Temporarily bridge PR336 to bypass PQ995 and feed a valid ID-level to the KBC for testing. Use only with a known-good 20 V Lenovo adapter and remove the bridge after diagnosis. [Elektroda, sk1977, post #16847434]

What should I verify on the BQ24737 charger?

Confirm BQ24737_VDD is present and that ACOK# is asserted low (active). Without these, the upstream FET chain will not enable, and system rails will not come up. Trace the enable sequence through the named FETs. [Elektroda, lisek, post #16845381]

My board lacks PU401; is my diagram wrong?

This board uses two SY8206BQNC devices for the 3.3 V and 5 V rails, not a single PU401 block. Locate SY8206 packages near the coil pair for 3.3/5 V to continue checks. [Elektroda, adamadi33, post #16845217]

How-to: quick power-up triage on NM-A273?

  1. Measure idle current; if ~20 mA, suspect KBC.
  2. Check ADAPTER_ID_ON#, PQ995 path, and bridge PR336 only for testing.
  3. Verify 3.3/5 V rails are present before pressing Power. [Elektroda, sk1977, post #16847434]

What finally fixed the case discussed in the thread?

The fault stack was PQ301, a bad KBC (replaced and programmed), and a rewritten BIOS. After these, the board resumed normal signaling and charging behavior. [Elektroda, janko23, post #16855812]

Edge case: the fan never spins but LEDs blink five times—what then?

Blink sequences with no fan can still point to ID-line or KBC issues. In the case described, repeated five-blink cycles preceded total loss of the power LED, and the repair required KBC and BIOS work. [Elektroda, janko23, post #16855812]
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