DVI problems

[WernerB]

I have a Sapphire AGP X1300 256M that has VGA and DVI outputs. It is rated at 1680 x 1050
60 Hz. The monitor is Scepter X22WG LCD which has a native resolution of 1680 x 1050,
60 Hz also and DVI and VGA inputs as well. As long as I use VGA, everything works nomally,
but DVI has major problems with anything higher than 1280 x 1024. The problem manifests
itself with flickering pixels and other artifacts all over the screen. It sounds like a timing
problem to me, but where in the chain, video card, cable or monitor? I would be greatful
for any advice or sugestions.
Thanks,
wb

 

[MrWizzard]

The only way to attack the problem is to start changing each of those things that you mentioned one by one and see when the problem disappears.

That could be difficult depending on what you have access to though.

 

[WernerB]

That is one solution that is pretty obvious, but I don't have spare monitors and video cards laying around.
Thanks anyway,

wb

 

[hmorphone]

I would swap out the DVI cable. There is one of those monitors, I forget if it's this one, that is notorious for coming with a faulty DVI cable.

 

[WernerB]

Thanks, I will give that a try, I have a DVI cable from my Samsung 171T monitor, which I have just retired for the 22" Sceptre.

wb

 

[xtknight]

Could be lack of bandwidth on the video card, faulty DVI cable (or you're using it too long distance), or a faulty monitor.

 

[WernerB]

Thank you all for your suggestions. It turned out to be a baaad DVI cable. Now, I have to fight with New Egg / Sceptre to get it replaced.
Wish me luck,

wb

 

[lotusbellicose]

How does it "turn out to be a bad DVI cable?"

VX922 with a 7800 GS card.

I just purchased a VX922, and with DVI, I cannot go past 1024x768. It is fine up to then, but if I select 1152x864 or higher, I get flickering pixels (mostly same color), outlines, and some embossing-type artifacts.

I suppose I can pull out an analog cable, but I was hoping to use DVI. If the ANALOG cable works with Analog mode, does it mean the DVI cable is bad?

Thanks.

 

[Peter]

With NVIDIA cards, the DVI signal might be poor straight from the source. The 7 series should be over that problem though. You'll never know until you've tried a known good cable.

 

[lotusbellicose]

Well, the analog cable works just fine. Bummer.

Later I will try to airspray out the ports and cable. Otherwise, I guess I'll e-mail Viewsonic for a new DVI.

 

[WernerB]

How does it "turn out to be a bad DVI cable?"

Probably poorly assembled, the bandwidth required is in the Gigabyte range and it
does not take much to screw the whole thing up.

wb

 

[lotusbellicose]

Guess it was a badly formed question. Guess my question was how one "finds out" it is a bad DVI cable; what process of elimination does one follow.

Haven't nabbed an airsprayer yet. If that doesn't work clearing out the vid card and cables, then I suppose it is Viewsonic-calling time on Monday.

 

[WernerB]

For once, customer service really seems to have worked. I may wind up with
two replacement cables. After some initial hesitation, New Egg appearantly thought better of it and has already shipped a replacement cable.

In the meantime, I complained to Sceptre and they informed me they are shipping a cable also.

Perhaps one or the other will actually work. I will keep my fingers crossed,

wb

 

[lotusbellicose]

Provantage.com won't do anything but give an RMA and accept the entire package in return for an entirely new VX922.

So... I sent an authentically pleasant e-mail to Viewsonic, requesting a replacement cable. We'll see how that goes. **update, the Q & A section did not look like it was going to Customer Service or Tech Support, so, I don't think it qualified as an e-mail.) I did find an e-mail address, vsparts at viewsonic dot com that requested model number and serial number with a request for replacement parts, though. See below**

With the weather (snow all over TX [these people don't know how to drive, help!!]), I've been stuck away from home since I had the issue, so I haven't had a chance to airspray the ports, reverse the cable. I'll be trying that this evening, and posting my results. Also, expect the Viewsonic response to get posted here.

 

[lotusbellicose]

Ports sprayed clean and cable reversed.
Friendly e-mail sent to Viewsonic. **This e-mail was sent back telling me to use their "new" Contact us page. Then I found a form on the contact US page @ Viewsonic... http://www.viewsonic.com/support/index.htm, then click the blue link "Click here for form in English." This brought up a form, which I hope will ACTUALLY FINALLY make it to Viewsonic..."**

Analog cable continues to work flawlessly.

Results on the DVI cable wax and wane, always erroring past the cutoff resolution.

We'll see what Viewsonic has to say.

 

[WernerB]

Well, the cable from New Egg arrived on Friday, 1/19 via ups 3 day service and it works flawlessly. I disected the defective cable and found that when they put the heatshrink
over those ferrite sleeves, (those fat lumps at each cable end) they partially melted the cable at on end. I t was not an actual short but a serious discontinuety in
the characteristic impedance of the cable at that point.

 

[Peter]

Excellent analysis. If the vendor cares, you should hand that detail feedback in for QA. (Good manufacturers are starving for input like this.)

Originally posted by: WernerB

A serious discontinuity in
the characteristic impedance of the cable at that point.

... and for the less technically inclined,

Originally posted by: TranslatorMan

The cable was teh b0rk.

 

[nullpointerus]

LOL

 

[WernerB]

Originally posted by: Peter
Excellent analysis. If the vendor cares, you should hand that detail feedback in for QA. (Good manufacturers are starving for input like this.)

Originally posted by: WernerB

A serious discontinuity in
the characteristic impedance of the cable at that point.

... and for the less technically inclined,

Originally posted by: TranslatorMan

The cable was teh b0rk.

I also received the replacement cable directly from Scepter two days a go and it works fine. It looks identical
to the defective cable, but this one works fine, no problems. So the bad cable I received originaly was apparently
an isolated incident.

Peter, as you might have guessed from my defect analysis, I am a retired electrical Engineer and I know how
important feedback from the field is in improving QC. The trouble with this supply chain and many other
similar ones, is that the feedback never gets back to the manufacturer. If I send them what I found, it
will go to their west coast address, which invariably consist of a sales office and a warehouse.
The information very rarely if ever gets back to the manufacturer, who is in China in this case.
Further more, the cable in all likelyhood was made by a subcontractor, so I am sure you get the picture.

wb

 

[Peter]

Yes I do, I'm a not-retired engineer in this industry ... I do know how important it is to have your local distribution feed the problems back to the factory - and I also do know how rarely this happens.

You got to start somewhere, and when there's no feedback at all, then the probability for improvement is zero. Provide feedback, and it is greater than or equal to zero