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  1. #1
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    820-3787 PPDCIN_G3H fluctuating around 2V

    Hi guys,

    I have this liquid damaged board here that makes me scratch my head. I seem to miss something here.

    I replaced u7100, U4850, U7090, Q7135, R7150, F7140, F7141. Also reworked the current sensing around u7100.

    PPDCIN_G3H is fluctuating around 2V.

    BUT ! If I remove U7100 I have green/orange light, stable 16,6V on PPDCIN_G3H, PP5V1_BIAS present and 3.41V on PP3V42_G3H.

    Resistors around U7100 measure all fine ( R7110 97k instead of 130k), no shorts.

    Any hints how to continue ?

    all the best, K

  2. #2
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    Re: 820-3787 PPDCIN_G3H fluctuating around 2V

    I removed again f7140 and f7141. On the ppbus side I have about 0.4 diode drop (final reading after 5 - 10 seconds) but if I switch the probes my values start negative and then going up. switching back again the same. means on ppbus ( or inherited bus) I have a beep for about 2
    1.5 to 3 seconds when switching the probes.

    Since removing theese filters I have:

    pp3v3_sus 0.5v

    ppvrtc_g3h 3.4v

    both quite zero before.


    I am reading more schematics and scratching my head....thinking of injecting ppbus. before I will inspect all main components on ppbus and the sub buses of it.

    CHGR_ACIN is 3.9v. Just saying. Dont know it this is a correct value.

    Never yet attached a battery.

    Relating the 2 v on ppdcin i descibed in the first post.....on attaching the charger it takes about 5 seconds before I have 16 V ( with u7100 soldered it remained fluctuating around 2v.)

  3. #3
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    Re: 820-3787 PPDCIN_G3H fluctuating around 2V

    check components around Q7180. if all ok replace Q7180.

  4. #4
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    Re: 820-3787 PPDCIN_G3H fluctuating around 2V

    hey gurmon, thanks for your answer. all components around q7180 and the mosfet itself look fine. all the surroundings measure fine. Do you think I should replace it even though I have ppdcin_g3h present (with delay indeed, as I described) without ISL beeing installed ?

  5. #5
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    Re: 820-3787 PPDCIN_G3H fluctuating around 2V

    if q7135 was shorted I am supposed to replace q7130 along with it, right ?

 

 

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