Patch Lady – who knew a cmos?

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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
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Susan Bradley Patch Lady/Prudent patcher

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GreatAndPowerfulTech

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

GaryK

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Perturbance

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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.

Windows - commercial by definition and now function...

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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…?

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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….

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

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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.

Always create a fresh drive image before making system changes/Windows updates; you may need to start over!

We all have our own reasons for doing the things that we do with our systems; we don't need anyone's approval, and we don't all have to do the same things.

We were all once "Average Users".

Computer Specs

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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

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[Canadian Tech]

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

• This reply was modified 4 years, 6 months ago by Canadian Tech.
• This reply was modified 4 years, 6 months ago by Canadian Tech.

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