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  • Patch Lady – who knew a cmos?

    Posted on Susan Bradley Comment on the AskWoody Lounge

    Home Forums AskWoody blog Patch Lady – who knew a cmos?

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      • #2306504 Reply
        Susan Bradley
        Da Boss

        So the other day someone plugged in a usb dongle to an HP Z240 workstation.  And it turned off.  And wouldn’t turn back on again. So I purchased a rep
        [See the full post at: Patch Lady – who knew a cmos?]

        Susan Bradley Patch Lady

        1 user thanked author for this post.
      • #2306506 Reply
        gkarasik
        AskWoody Lounger

        Just had a power supply die last week. Where are we now astrologically?

        GaryK

        1 user thanked author for this post.
      • #2306507 Reply
        Microfix
        AskWoody MVP

        Reading the supplied manual or pdf is usually my 1st port of call.
        I much preferred the CMOS short jumpers on a 3 pin header method.

        No problem can be solved from the same level of consciousness that created IT - AE
      • #2306527 Reply
        anonymous
        Guest

        The laptop I used in college (this particular one predated USB ports, in fact) once failed hard in between one use and the next. I shut it off to go have lunch, and after lunch it wouldn’t turn back on. No BIOS screen, nothing at all, not even a beep.

        Eventually, when I got through to a real tech support person, I was told to unplug the laptop, remove the battery, and hold the power and reset buttons for 60 seconds. I did, and it worked; the laptop booted just fine, and continued in service until it was finally time for a newer, faster one.

        I have no doubt that a CMOS clear was what I accomplished, but as to what caused the original problem, I never did have any clue. A stray cosmic ray, for all I know.

        So, I sympathize with your experience. It might be that a physical problem with the USB drive/port triggered your failure, but then again…?

      • #2306539 Reply
        Simon_Weel
        AskWoody Plus

        Ah, the HP z240 with it’s proprietary power supply connectors. Nice going, HP. To fit a regular off the shelf power supply, you need an adapter cable. And when switched on, the BIOS doesn’t detect the power supply fan, nagging you to press F1 to continue….

      • #2306562 Reply
        agoldhammer
        AskWoody Plus

        For those of us who build our own work stations, the CMOS battery is the first thing to do when a weird problem happens.

      • #2306621 Reply
        bbearren
        AskWoody MVP

        More than a decade ago, when I was still doing computer repair on the side, I replaced the PSU on a client’s HP twice.  On both occasions, HP diagnostics indicated the PSU as being the culprit.  I had replaced the CMOS battery the first time I had it.

        When it died the third time and my client called asking if I knew what I was doing, I had very recently purchased a PSU tester.  I brought his HP to my shop and tested the PSU, it was all good, correct voltages everywhere, yet the HP diagnostics said “Bad PSU”.

        I replaced the motherboard, and that cured the problem.

        Create a fresh drive image before making system changes/Windows updates, in case you need to start over!
        "When you're troubleshooting, start with the simple and proceed to the complex."—M.O. Johns
        "Experience is what you get when you're looking for something else."—Sir Thomas Robert Deware

      • #2306699 Reply
        GreatAndPowerfulTech
        AskWoody Lounger

        I’ve seen this issue ma few times over the years.  A PC won’t start. Testing the power supply comes first. If that doesn’t work I pull the 2032 battery and clear the CMOS via jumpers or the motherboard short. About ten percent of the time that does the job. I presume that the always-on low voltage, of todays computers, somehow sees a USB, or other, short as code that “confuses” the CMOS. That’s the only explanation I came up with. Maybe an electrical engineer here can explain it better.

        GreatAndPowerfulTech

      • #2306827 Reply
        Canadian Tech
        AskWoody_MVP

        I have never seen a MB with a CMOS reset switch. Sounds like a good idea. I have however seen cases in which CMOS is the culprit. CMOS batteries issues can cause a plethora of strange behaviours.

        99% of CMOS batteries are a standard 2032. I buy the branded ones on Amazon.ca for about $0.70. Really not expensive.

        On desktops, I replace the 2032 as routine maintenance after about 4 years. When I replace it, I use a sharpie to put a date on it. After that, I replace them after about 3 years. Simple and cheap.

        On laptops, very different story. A few can actually be seen and removed easily, but very few. Most are buried deep and require a lot of disassembly just to find. Then in almost all cases you find a battery encased in shrink wrap with leads soldered and leading to a plug, which goes into the MB. That is an OEM part that you may or may not be able to find and may cost $20. I found a simple way. I remove the battery assembly. Cut off the shrink wrap. Carefully pull the leads off the old battery. Then use very thin copper tape to tape those leads on to a new 2032. Then cut off a short piece of shirnk tubing over the battery with leads taped on. Then apply the heat to shrink the tubing. Trim excess if needed.

        CT

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