I have an AIO HP 24-xa0057C (bought at Costco). The screen usually flickers with horizontal patterns

[LeisureSuitLarr]

I have an AIO HP 24-xa0057C (bought at Costco). The screen usually flickers with horizontal patterns, but sometimes, occasionally, works perfectly. I noticed that the little blue light on the back above where you plug in the power cord, flickers somewhat in synch with the times that the screen flickers. Does that mean I probably have a bad power supply or power connection?

[itsmyname]

@LeisureSuitLarr -- Does that mean I probably have a bad power supply or power connection?

I would suspect the latter. 

Can you plug the power-cord into a different wall-outlet, or to a different socket in your power-bary?

> bought from Costco

How long ago?

If something like a week, exchange it at Costco.

If less than a year ago, exercise the HP Warranty to get it repaired/replaced, at HP's expense.

[LeisureSuitLarr]

It’s beyond any return or warranty window, since I bought it about 3 years ago.  I’ve tried it in multiple power outlets.  I took it to a repair shop and he had it several weeks and couldn’t figure it out.  He replaced the monitor 3 times, the internal display connector once.  He didn’t consider that it might be a bad power supply, but it makes sense to me considering the way the blue light flickers in the back.  I haven’t checked it with the voltmeter, because even if it reads 19.5V it might not maintain that voltage under a load, and I’d have to open up the case to take a voltage reading under load.  I’ll do that if another power supply gives me the same result.

[itsmyname]

@LeisureSuitLarr --  I’d have to open up the case to take a voltage reading under load.  

Maybe you do not have to open it up.

I have a "RioRand(r) Monitor Energy Consumption & Cost Electrical parameter Display" device.

Web-site: www.RioRand.com

It connects into a wall-outlet, and you plug your device into its three-prong female socket.

It shows the power-levels going "through" it, on its screen.

Hopefully, you don't have a major electrical problem in your home's "circuit-breaker box".

I have 220 Volts coming into that box, on three wires (positive, negative, ground).

The "positive" and "ground" connect into the 10 circuit-breakers on the left-side panel.

The "negative" and "ground" connect into the 10 circuit-breakers on the right-side panel.

My 220 V devices, e.g., clothes-dryer, connect to "positive" and "negative".

My problem was a frayed wire into one panel of the breaker-box, causing major power-fluctuations to all the electrical outlets into some of my rooms.  I had to get an electrician from the provincial power-company to rewire my house, from the "periscope" (one end of the main feed from the nearest telephone-pole) into both sides of my breaker-box.  I am quite happy that the frayed wire did not cause an electrical fire!

[LeisureSuitLarr]

I opened up the case and could not find an easily identifiable place to tap into the incoming 19.5v dc unless i got access to the back of the motherboard, which would be a real difficult thing to do with this model. And I'm afraid of shorting something out on the top side of the motherboard if I go probing willy-nilly, since everything is so small including the traces.

I took voltage readings across the power diode that lights up with power.  It was measuring 5-6 volts when on steady, and varied down to about a half a volt when it was off or flickering once I turned on the power button to the computer.

That obviously explains why the light was not on steady but if the power to the diode is getting corrupted, what is the next logical step to check to fix my flaky monitor problem?   If the voltage is being drawn down like that for the diode, then why do all the other computer components seem to be working ok except for the internal display?  It would seem that other components would be compromised if something on the motherboard was messed up and overloading the amp draw to the point of sucking the voltage down like that?

[itsmyname]

@LeisureSuitLarr -- just a guess, but what if you purchase a UPS, and connect your computer's power-cord to the UPS?  That should give you "smooth" power into the power-adapter.  Have you tried a different power-cable (or power-brick) ?

[LeisureSuitLarr]

I tried another power brick and power cord and got the same result.

I'm thinking that it almost has to be the motherboard.  With the AIO computer with an intermittent screen flickering problem,

it almost has to be either the power, the motherboard or the display.

The HDMI out external display works fine.

Since I've replaced the power brick, and the repair tech tried replacing 3 internal displays, that either leaves the motherboard or something I am not considering, right?  The alignment of the stars to the moon?

I've reloaded all of the drivers including the display drivers, and reset the system to factory.  I believe that I re-flashed the BIOS but it's been a couple months, I can't remember for sure.

[itsmyname]

@LeisureSuitLarr -- it almost has to be either the power, the motherboard or the display.

I think that you have ruled-out a "power" issue.

If the output seen on the 3 displays is always "corrupt", it's probably not the displays themselves. Maybe, the cable that connects the display to the motherboard is physically damaged, or not fully-connected at both ends?

If the external HDMI-output is fine, then some of the "integrated display" circuits on the motherboard are OK. Without a detailed diagram of the motherboard's circuits, one does not know if there are separate circuits on the motherboard for the "internal" versus the "external" display.

[LeisureSuitLarr]

the repair guy said he also tried swapping out the connector from the motherboard to the internal display.  His thesis was that, as you have said, maybe it was a loose or damaged connector.  Sorry I did not mention that.

So yes, it seems logical to me that if I am getting a randomly flashing or on or off blue power light on the back when the PC is on then something is going on with the motherboard.

I don't know if it a coincidence but this problem started after working fine for maybe 3 years, right after my daughter used the integrated flash card reader for the first time.  She had no problem using it, but then the problem started.  It makes no sense to me that there would be any cause/effect from that.

I'm to the point where I might have to pay HP the $99 for the one-time service call fee, but I'm not confident that even they would know how to help me, based on some of the reviews of that service.

[itsmyname]

@LeisureSuitLarr --  It makes no sense to me that there would be any cause/effect from that.

Once, I inserted a damaged USB device into a USB socket on my computer. 

It turns out that it had an electrical short-circuit inside it.

That short-circuit "burnt-out" some circuits on the motherboard, causing that USB socket to go "dead".

So, that is "cause-and-effect" in my case. Maybe yours, too.

>  if I am getting a randomly flashing or on or off blue power light on the back when the PC is on then something is going on with the motherboard.

If that lamp is part of the power-supply, I would be concerned about the power-supply, not the motherboard.

Is your computer connected to a "surge-protected" power-bar, or to a UPS (Uninterruptible Power Supply) ?

Either device should provide "smooth" power to the power-supply. 

Maybe, "non-smooth" power is causing the lamp to blink ???