Flickering single display in multi-head XRandR setup

Gene Heskett gheskett at wdtv.com
Fri Mar 25 13:29:54 UTC 2016

On Friday 25 March 2016 07:19:44 Andreas Mohr wrote:

> Hi,
> On Fri, Mar 25, 2016 at 11:03:36AM +0100, martin f krafft wrote:
> > Hi Andreas,
> >
> > Thank you for taking your time to reply. I've since followed up
> > having found the problem, and I think it must be one of the DP ports
> > on the graphics card.
> Ooook.
> > Now, you write:
> > > Perhaps unthinkable, but the connectors of the card might be
> > > implemented / wired up asymmetrically, e.g. due to an ickily
> > > varying length of traces, or EMI issues.
> >
> > This leads me to believe that the connector hardware itself could be
> > at fault. Seriously, is DP *that* finicky and subject to connection
> > failures? I'd have thought that it being 2016, the industry would
> > have finally gotten the hang of it, especially after screwing up
> > HDMI so badly.
> Hmm, I was writing that focussing on PCB-side implementation etc.,
> but of course mechanical connection issues (including soldering
> issues) likely are more dominant (when doing failure diagnosis,
> one likely should focus on more "mechanical" / electro-physical parts
> such as connectors, fuses, capacitors, transformers, ... initially,
> since these are much more prone to failure
> due to their inherent wear and tear - movement, thermo-related etc.).
> Nice to hear that this seems nailed now.
> Andreas Mohr

Speaking as a Certified Electronics Technician, which I am, I can often 
refine the mechanical part, not to a flaky connector, although its 
possible, but far more often it will be found to be a surface mounted 
low voltage electrolytic capacitor that has failed by loss of an 
internal connection.  Overall, the failure rate of those is 100x that of 
any other part on the average PCB. The failure mechanism is a high 
Equivalent Series Resistance, and it takes a meter designed to read this 
ESR, to find the problem, something 99.9% of the digital meters today do 
not have as its a completely different circuit that measures it.  
Special meters that do measure it can be had even as a kit you build, 
but the best of the lot is the Capacitor Wizard, at about $200 USD a 

Worse, the U.S. industry, since General Cement is gone, cannot sell me a 
tweezer-like soldering iron needed to remove them so fresh ones can be 
put in their place.  And even the GC iron sold 20+ years ago had to be 
run on a powerstat set for as low as 60 volts else it ran so hot it 
destroyed the board.

That is why so much of our electronics is now a one shot deal, plug it in 
and use it till it fails, and when it fails, go to the store and get 
another to plug into that function/position.  No repair is possible at a 
cost that makes repairing it feasable.  Toss in that such people are a 
dying breed and are not being replaced by the younger generation. I did 
do that, since 1949 for a living, but now at 81, my hands are losing the 
steadiness needed.

Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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