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Flickering on music PC screen

I am using a CAPS (Computer Audiophile Pocket Server) v2 as a music player (http://www.computeraudiophile.com/content/405-computer-audiophile-pocket-server-caps-v20/).

The problem I am having at the moment is with some screen flickering. The monitor is a BenQ 24" TFT connected via VGA cable to the CAPS. The flickering is fast, over the whole screen and not obvious unless you look carefully. It is more pronounced with light colours. The flickering is constant and seems to worsen (I think) with increased CPU activity.

I don't think that it is the monitor or the cable (I have tried the monitor with a different source, and have used a different cable).

One other potential clue - some time ago I had a problem with a (very) high-pitched constant noise coming from the CAPS. After much investigation I finally located the source - an internal component called the "external drive magnetic buzzer", labelled AC-1205GG. There was a small hole on top of this component, and when I covered this with glue the noise mostly disappeared.

I wonder if these two problems are related, as they both seem to be due to some kind of electrical noise getting through. My knowledge of electrical engineering is poor however and I'm not sure to go from here. I did wonder if it is a grounding issue but I don't know how to test this. Any help greatly appreciated!

Thanks

Flickering on music PC screen

Reply #1
That link won't load for me but if possible don't use VGA. A cheap video card can easily cause poor image quality on VGA. If you must, set the resolution lower.

Flickering on music PC screen

Reply #2
Is the video card driver installed correctly?  On that system it should be an Intel GMA 3150.  If device manager says you have a Standard VGA adapter then the driver is not installed correctly and the video performance will suffer greatly.

Flickering on music PC screen

Reply #3
Thanks for the replies.

Saratoga - VGA is the only output on the CAPSv2. I require the native resolution of the monitor for display purposes. I tried your suggestion of reducing the resolution anyway - and tried a few different ones - but this had no effect on the problem.

Washu - I checked the video card driver - and it says Intel Graphics Media Accelerator 3150 - which is the one you mention.

Any more suggestions much appreciated! Any any comments on the grounding issue?

Flickering on music PC screen

Reply #4
Lately I have seen quite a few posts about DAWs on this fourm when they are more suitable on KVRaudio, Gearslutz and TapeOP. Are there any plans to make it more clear to people that this site is about audio codecs and things similar to that and not computer problems? If I am wrong about the purpose of this site then please correct me.

EDIT: Forgot one word.

Flickering on music PC screen

Reply #5
Saratoga - VGA is the only output on the CAPSv2. I require the native resolution of the monitor for display purposes.


Not going to happen with that monitor.

I tried your suggestion of reducing the resolution anyway - and tried a few different ones - but this had no effect on the problem.


How low did you go?  For cheap VGA, I would try 1024x768 and compare.  Back in the day you could get good quality higher with VGA, but a good video card was essential.

Washu - I checked the video card driver - and it says Intel Graphics Media Accelerator 3150 - which is the one you mention.


Thats not going to matter.

As well as using low resolutions to reduce the effect of poor analog quality on the VGA output, I would also try your monitor in another PC with VGA just to make sure the VGA input on it works ok.  Finally, trying a different monitor entirely might not hurt. 


Flickering on music PC screen

Reply #7
I am using a CAPS (Computer Audiophile Pocket Server) v2 as a music player (http://www.computeraudiophile.com/content/405-computer-audiophile-pocket-server-caps-v20/).

The problem I am having at the moment is with some screen flickering. The monitor is a BenQ 24" TFT connected via VGA cable to the CAPS. The flickering is fast, over the whole screen and not obvious unless you look carefully. It is more pronounced with light colours. The flickering is constant and seems to worsen (I think) with increased CPU activity.

I don't think that it is the monitor or the cable (I have tried the monitor with a different source, and have used a different cable).

One other potential clue - some time ago I had a problem with a (very) high-pitched constant noise coming from the CAPS. After much investigation I finally located the source - an internal component called the "external drive magnetic buzzer", labelled AC-1205GG. There was a small hole on top of this component, and when I covered this with glue the noise mostly disappeared.


That device is supposed to provide a short term ca 90 dB SPL  ca. 3 KHz tone for information or as a warning. It should not be activated all the time and it should not affect video quality.

The problem you describe may be due to a defective display - its backlighting subsytem may be failing to provide a steady source of illumination. Have you tried another display?

Flickering on music PC screen

Reply #8
Dodgy VGA output on the CAPSv2?

At work, one of my monitors is a 22" 1080p and that runs without issue over VGA, just the cable that cable with it.

Have you checked what is actually being output? There's normally some way on the monitor to display refresh rate etc. Some are more detailed than others. Being VGA it should have an auto-adjust setting to let it sync itself. I assume you've tried all this?

Flickering on music PC screen

Reply #9
It might be a noisy source signal. I had a TV that flickered when using VGA output from a laptop when the power adapter was still connected to the laptop. When I removed the power from the laptop the flickering almost disappeared completely.
HDMI/DVI to the TV did not have this issue.

Flickering on music PC screen

Reply #10
Is it a CRT monitor by any chance?  If so, try upping the refresh rate to however high it goes - the default is usually 60hz which flickers on a lot of CRTs, that can usually be bumped up to 75hz or 80hz.

LCD monitors wouldn't flicker due to the refresh rate - but a bad backlight sounds plausible. Try hooking up a different monitor (at the same resolution and refresh rate) if you have one.

Flickering on music PC screen

Reply #11
Monitors with PWM-controlled backlights may produce flicker.
http://www.youtube.com/watch?v=RlUHBQDlYgA

Flicker Free Monitor Database
http://www.tftcentral.co.uk/articles/flick...ee_database.htm

Last week I and my colleagues went to a restaurant with LED lighting, most of them did not notice the flicker but I noticed that. The whole environment looked like virtual reality (Matrix?), everything have a "frame rate" and I was scared and left. My colleagues said those are my illusions but I've proved they were wrong. Some LED lights do have visible flickering.
http://www.youtube.com/watch?v=C12QxTJL1KU

Flickering on music PC screen

Reply #12
My guess is that motherboard's built-in power supply is just noisy (in an acoustic sense). Also check the AC brick itself: Mine emits a high-pitched squealing noise. Not sure about the monitor flickering (ground loop?). I have seen shimmering VGA video when connecting to modern displays, but usually over longer cable runs.

I think that device you glued over is supposed to emit diagnostic tones, and it wouldn't be subtle if it were doing that.

Oh, and for what it's worth from someone who spent way too much money building a pair of deluxe ITX PCs: These days I seek out readymade solutions first (Intel NUC, Shuttle X50 et al) as they can be had for a fraction of the price and may wind up working better. Yes I own an Origen M10 case and it looks very nice, but in retrospect (and in the spirit of the HA way of doing things!), more and more, I'm seeing the beauty in spending money on things that actually matter and not fetishizing the hardware so much.

For instance, here's a cheap fanless notebook PC from Hewlett-Packard, it's got a faster dual-core processor and the price includes a 32 GB SSD and Windows license:

http://store.hp.com/webapp/wcs/stores/serv...am-notebook-11#!

BTW,  the extra cost of Windows 7 Pro or Ultimate is of no value whatsoever in this application unless (bragging rights aside) you need to connect your music PC to a domain controller or need the security of BitLocker disk encryption.

Flickering on music PC screen

Reply #13
Really appreciating all the input here. Apologies for the delay in this reply. I am still experiencing the same problem and have been trying bits and pieces to no avail. I tried a ferrite core around various cables, but no help. To address the points raised since my last message:

saratoga: I tried a bunch of resolutions, including 1024x768. There was no difference with any of them - the same flickering continued. I tried connecting a laptop to the same monitor via VGA; the problem was actually still there but much better, to the degree that it wasn't really a problem. I don't have a different monitor at the moment to try.

bennetng: I looked at the youtube video of the Benq screen flicker. That looks like roughly the same kind of problem as mine - though I wouldn't say that mine is as bad as how the screen appears in the video. My screen is an Asus PA248Q - not particularly old and it gets very good reviews online. I can't imagine that this problem is just normal for the monitor.

probedb: I have tried both the available refresh rates on the monitor - 59Hz and 60Hz - makes no difference to the problem.

LithosZA: interesting point about the problem with the power adapter - however I cannot remove the power adapter, as then the machine would have no power.

slks: no it is not a CRT monitor - it is an Asus PA248Q - http://www.asus.com/uk/Monitors_Projectors/PA248Q/. As mentioned above, I don't have a different monitor to try just now.

bennetng: really interesting stuff about PWM monitors; I looked at http://www.tftcentral.co.uk/reviews/asus_pa248q.htm, which analyses the PWM at different brightnesses. It says that at 100% brightness there is no PWM and hence no flicker. I eagerly tried increasing the brightness of my monitor to 100% - but to no avail; the problem remains. I also tried adjusting most of the other possible settings, but no help.

4season: interesting about the motherboard's power supply being noisy. I checked the power brick and there is no audible noise from the brick.

Thanks again for the input. I am still here with the same problem. Hope the above replies help to get closer to the answer!

D



Flickering on music PC screen

Reply #14
Not sure if anyone is still reading this, but some more testing. I tried a VGA to HDMI converter (a small fairly cheap one that is USB powered, but got good reviews on Amazon) - though the flicker was still there! Appreciate any further advice if anyone is reading still.

 
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