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johnnylotto
Member
Last Activity: 04-06-2025, 06:27 PM
Joined: 09-17-2022
Location: Yellville, AR
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  • johnnylotto
    started a topic ASUS K5504VN main board schematics and boardview
    in Schematic Requests ONLY!

    ASUS K5504VN main board schematics and boardview

    Hello, I'm looking for main board ASUS K5504VN revision 2.1 schematics and boardview, for laptop ASUS Vivobook S 15, model K5504V notebook PC.

    [ATTACH=JSON]{"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":3523605}[/ATTACH]
    [ATTACH=JSON]{"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":3523606}[/ATTACH]​Hello, I'm looking for main board ASUS K5504VN revision 2.1 schematics and boardview,...
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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    Finally got some time to follow up and finish this up!

    I'm writing from my now fixed laptop -- all good again! Woo! Amazing what havoc a tiny little scratch that the eye can barely see can do!

    Today I practiced microsoldering a small wire jumper on a practice microsoldering board and coated with UV mask, all went well.

    Then I moved on to the damaged motherboard itself. The two adjacent components were so close to each other with a partial trace still between them that a sturdy solder bridge...
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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    Thank you! I'll give the wire a try!
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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    Woohoo! I think I've got the problem figured out!

    The scratch has disrupted low resistance electrical continuity between PC207 and PJ34 on the board. PJ34 carries 3.4V on the positive side, and this should be going to PC207 positive side, but only ~0.5V is measured. That voltage on positive PC207 goes directly back to the enable pin of PU21. Measuring resistance between those two components when the board is not powered shows open and it should be a short. See attached.

    So while the microscope shows the...
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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    I've received the microscope and am giving it a try. Really impressed. I can actually see the board clearly now, imagine!

    I've taken some screenshots of the area both while dry and while wet with 99% isopropyl alcohol (isopropanol). While the board is wet with alcohol the visibility of the traces is increased.

    In case I need to do some microsoldering once I figure out root cause, I've ordered a JCID AIXUN T3B Intelligent Soldering Station With T210 Series Handle (youtube review [url]https://www.youtube.com/watch?v=Ds2Xq3dwV30[/url]),...
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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    Just ordered this CCD microscope kit to try:

    [url]https://www.amazon.com/HAYEAR-C-Mount-Industry-Microscope-Soldering/dp/B08BF8DC6H[/url]

    Should have it by the weekend.

    More toys! I mean, tools!
    Re: System76 partial power-on, VDD1..../> More toys!
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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    Oh awesome! I didn't know that about the "*", thank you for pointing that out.

    I ordered a pair of ultra fine multimeter probe tips last night as my current probes are too thick to make it easy to measure the small components and close pins.

    I've started shopping the microscope. I'm thinking I'll choose a digital microscope with a CCD camera and USB/HDMI interface rather than stereoscopic microscope for PCB. My price range will probably be around $200 - $300 USD (maybe a bit more) which looks like...
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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    Hi @Sephir0th:

    You're correct about me confusing the pins on PU19: when measured from proper pin 1 of PU19, voltage is ~3.4V, matching what I see on PR225, so mystery solved there, thank you.

    PR225 is indeed that far away from PU21 -- see attached image with layout markings highlighted in red.

    With power off, I did measure from the topside of PC207 (non-ground side of the missing cap solder point) to pin 11 on PU21 which looks like it should be a direct connection, and I get about 1.5 Ohm...
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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    Thanks @Sephir0th! I don't have a digital microscope yet, but think I'll begin shopping one and will probably have one within a few weeks for better pictures. I work fairly long hours during the week, but hopefully I'll get a chance to follow up on your suggestions tonight. More soon!
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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    Hi @Sephir0th, thanks! This is my first time looking at a motherboard in detail and I'm finding this quite challenging to determine to failure and solution! The 3.3VA output appears to have about 1.86 kOhm resistance to ground as measured from PJ6 and also one side of C356, so that seems to be ok.

    [B][U]TLDR Summary:[/U][/B]
    1) PC207 is missing from the board, likely due to an initial forceful fan connector removal
    2) PR225 is giving the same voltages on each end of the resistor when the board is powered...
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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    Thanks for the suggestions @mon2!

    1) EN pin 11 reads about 0.48V, and fluctuates around a little bit. This measures about the same immediately after providing AC power, and also after pressing the power-on switch.

    2) With no power, both sides of PL16 inductor which comes from pins 16, 19 and 20, measure about 40 Ohms to ground.

    Since this problem started, the white color power-on indicator LED mounted next to the power button at the top right of the keyboard area has never come on -- the only...
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    Last edited by johnnylotto; 09-18-2022, 01:22 PM.

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  • johnnylotto
    replied to System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices
    Re: System76 partial power-on, VDD1.05 out fail

    After reviewing the forum further, it appears I can upload the service manual for this MB with schematics. Attached....
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  • johnnylotto
    started a topic System76 partial power-on, VDD1.05 out fail
    in Troubleshooting Laptops, Tablets, and Mobile Devices

    System76 partial power-on, VDD1.05 out fail

    [B][U]Laptop:[/U][/B]
    Hello, I have a System76 Gazelle laptop (model gaze14) which now only partially powers on and does not boot properly.

    [B][U]History:[/U][/B]
    This laptop has served me well for a few years. It's always been a bit noisy with the fans and recently became much more so on both fans, where just opening a vim/notepad session would cause the fans to spin up loudly and make a grating sound, like the ball bearing were mechanically wearing out. So after blowing the dust out of the fans out didn't help, I ordered replacement fans and heat sink component    ...
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  • johnnylotto
    replied to New Members - please post your introductions here
    in Announcements & Related News
    Re: New Members - please post your introductions here

    Hello! New member here from central US: Yellville, Arkansas, in the Ozarks. I work in IT, but on the software side, mostly devOps and SRE, although I have some background experience with electronics in general and computer hardware from quite a few years ago. A non-booting laptop has made me seek this forum out for further electronics education and expertise .
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