Solved Video Interference

jefflongo

Broke BitBuilt
Staff member
.
.
Joined
Dec 15, 2016
Messages
1,017
Likes
1,361
Location
Santa Barbara, CA
Portables
3
So I noticed that there's some interference on my video signal. After moving stuff around while it was on, I diagnosed that the source of the interference is my custom regulator coming too close to the video line. I used some shielded cable for the video line from an official Nintendo AV cable to try to prevent this.

I connected only one end of the shielding to ground (I'm still unsure if you're supposed to ground both ends.. Some say yes others say no because of ground loops or something, also I don't really have a place to ground the other end as the video line is connected to a switch to switching between internal/external AV and yes I could connect the ground on those cables together but it seems rather unsafe to have ground that close to other connections and 5v for the screen on the other end of the switch). Regardless, the shielding clearly isn't doing its job. What can I do to fix this?20170421_121120.jpg 20170419_135244.jpg
 

Shank

Moderator
Staff member
.
.
Joined
Jan 31, 2016
Messages
1,286
Likes
2,723
Portables
6
Is your regulator causing airborne interference or electrical interference? Move the regs as far away from the video signal as you can. If you still get interference, then it is electrical, otherwise, it is airborne. Most airborne interference on the regulators comes from the inductor, and can often be solved by moving the regulator as far away from the video line as possible. If its electrical, you are in for a tough time.

On a project I had, a custom regulator was causing nasty airborne interference, and I couldn't move the regulator. I helped reduce it by bending some sheet aluminum into a box around the offending regulator and grounding it. It added some mass and weight, but it solved my problem.

I was told that adding an inductor in series can help clean up a voltage signal. Just be sure to add inductive spiking protection. Other ways to clean up a dirty voltage signal include running capacitors of varying sizes between the signal and ground, and filters.
 

jefflongo

Broke BitBuilt
Staff member
.
.
Joined
Dec 15, 2016
Messages
1,017
Likes
1,361
Location
Santa Barbara, CA
Portables
3
Is your regulator causing airborne interference or electrical interference? Move the regs as far away from the video signal as you can. If you still get interference, then it is electrical, otherwise, it is airborne. Most airborne interference on the regulators comes from the inductor, and can often be solved by moving the regulator as far away from the video line as possible. If its electrical, you are in for a tough time.

On a project I had, a custom regulator was causing nasty airborne interference, and I couldn't move the regulator. I helped reduce it by bending some sheet aluminum into a box around the offending regulator and grounding it. It added some mass and weight, but it solved my problem.

I was told that adding an inductor in series can help clean up a voltage signal. Just be sure to add inductive spiking protection. Other ways to clean up a dirty voltage signal include running capacitors of varying sizes between the signal and ground, and filters.
Well when I physically move the regulator away from the video signal line the interference disperses so it sounds like it's airborne. I don't think I could put aluminum around the regulator because the bottom would surely short (see pic). And I don't really see how I could move the regulator anywhere else in the case. I just thought shielding the video cables would have sorted this out.

20170328_160145.jpg
 

JacksonS

.
.
.
Joined
Feb 17, 2016
Messages
301
Likes
576
Location
Boston, MA
Portables
6
Try connecting ground to the other end of the shielding. It shouldn't be able to cause any issue unless you have a poor ground connection somewhere else. When you put it all inside a case, you can route the video cable away from the regulators.
 

jefflongo

Broke BitBuilt
Staff member
.
.
Joined
Dec 15, 2016
Messages
1,017
Likes
1,361
Location
Santa Barbara, CA
Portables
3
Try connecting ground to the other end of the shielding. It shouldn't be able to cause any issue unless you have a poor ground connection somewhere else. When you put it all inside a case, you can route the video cable away from the regulators.
I'll try grounding the other end. The issue is that the place where my regulator has to reside is very close to the source where video is pulled from so I may not be able to separate the two so well.
 
Joined
Apr 29, 2016
Messages
83
Likes
100
I always connect both ends of the shielding to ground and I do not experience interference as a result. Judging by your set up, the best way to do this would be to use a DPDT Switch instead and use 1 pole for the ground connections and the other pole for the signal.

Also, I would recommend more than just 1 ground connection between the motherboard and the screen. I typically wire no less than 3 ground wires to the screen (1 from the MB to the Screen Control Board, 1 to complement Power and 1 to compliment the video signal.
 

jefflongo

Broke BitBuilt
Staff member
.
.
Joined
Dec 15, 2016
Messages
1,017
Likes
1,361
Location
Santa Barbara, CA
Portables
3
I always connect both ends of the shielding to ground and I do not experience interference as a result. Judging by your set up, the best way to do this would be to use a DPDT Switch instead and use 1 pole for the ground connections and the other pole for the signal.

Also, I would recommend more than just 1 ground connection between the motherboard and the screen. I typically wire no less than 3 ground wires to the screen (1 from the MB to the Screen Control Board, 1 to complement Power and 1 to compliment the video signal.
Yeah right now I'm using a DPDT switch for video signal and power to the screen so that I don't have an ugly blue screen on wasting power when using AV out. Trying not to use multiple switches to accomplish for 1 task but I mean I suppose I could try to find a 3pdt switch. I'll worry about that later. I'll put more ground on the screen as well although I wasn't seeing any issues with it.
 

Madmorda

Painting Queen
.
.
Joined
Oct 27, 2016
Messages
725
Likes
1,718
Location
Texas
Portables
2
My gcp suffered from intermittent interference ranging from very light to extremely annoying. I still have it very occasionally very lightly, but shielding my video cable and moving it farther away from my regulators made it significantly better. In my wiip, the regs are all crammed into a corner awkwardly so I can avoid this as much as possible. If you can't make it go away entirely, you could try using shielded wire for the power line to the screen as well just in case.
 
Joined
Apr 29, 2016
Messages
83
Likes
100
Yeah right now I'm using a DPDT switch for video signal and power to the screen so that I don't have an ugly blue screen on wasting power when using AV out. Trying not to use multiple switches to accomplish for 1 task but I mean I suppose I could try to find a 3pdt switch. I'll worry about that later. I'll put more ground on the screen as well although I wasn't seeing any issues with it.

Did your screen's controller board come with a control panel? Those usually have a power switch that you can use. I ask because using multiple switches for this is essentially unavoidable UNLESS you use a switching TRRS port for Video out. Then the switch for that can be used for the screen and video when a TRRS cable is plugged in.
 

jefflongo

Broke BitBuilt
Staff member
.
.
Joined
Dec 15, 2016
Messages
1,017
Likes
1,361
Location
Santa Barbara, CA
Portables
3
My gcp suffered from intermittent interference ranging from very light to extremely annoying. I still have it very occasionally very lightly, but shielding my video cable and moving it farther away from my regulators made it significantly better. In my wiip, the regs are all crammed into a corner awkwardly so I can avoid this as much as possible. If you can't make it go away entirely, you could try using shielded wire for the power line to the screen as well just in case.
I don't think that shielding the power line would make a difference because the interference occurs when the regulator itself is course to the (already shielded) video line
 

Madmorda

Painting Queen
.
.
Joined
Oct 27, 2016
Messages
725
Likes
1,718
Location
Texas
Portables
2

jefflongo

Broke BitBuilt
Staff member
.
.
Joined
Dec 15, 2016
Messages
1,017
Likes
1,361
Location
Santa Barbara, CA
Portables
3

Madmorda

Painting Queen
.
.
Joined
Oct 27, 2016
Messages
725
Likes
1,718
Location
Texas
Portables
2
Could it be the ground then? I'm assuming you've got both your composite signal and ground going to the external screen.

I'm just throwing out ideas since your shielded wire isn't doing what it's supposed to. Assuming you used good quality cables and have both ends of the shielding grounded, all I can think of is power/ground interference, or else you'll have to move the regs away or deal with the interference.
 

ShockSlayer

the real
.
.
Joined
Jan 16, 2016
Messages
1,512
Likes
3,940
Location
standing up
Portables
please do not ask!!!! I will NOT respond
Use shielded wire for each voltage line coming off of the regulators. Your picture shows only 1 ground going in for 3 regs, that's probably why.
 

jefflongo

Broke BitBuilt
Staff member
.
.
Joined
Dec 15, 2016
Messages
1,017
Likes
1,361
Location
Santa Barbara, CA
Portables
3
Could it be the ground then? I'm assuming you've got both your composite signal and ground going to the external screen.

I'm just throwing out ideas since your shielded wire isn't doing what it's supposed to. Assuming you used good quality cables and have both ends of the shielding grounded, all I can think of is power/ground interference, or else you'll have to move the regs away or deal with the interference.
Yeah I haven't grounded both ends of the wire, cause I was originally told not to but I'm going to try it tomorrow.
 

ShockSlayer

the real
.
.
Joined
Jan 16, 2016
Messages
1,512
Likes
3,940
Location
standing up
Portables
please do not ask!!!! I will NOT respond
Wait, who told you not to?
 

jefflongo

Broke BitBuilt
Staff member
.
.
Joined
Dec 15, 2016
Messages
1,017
Likes
1,361
Location
Santa Barbara, CA
Portables
3
Wait, who told you not to?
if only one side is grounded, than it is just a wire. There needs to be a connection on both sides for current to flow. that is how it works afaik.
edit: I just googled it and I may be wrong in this circumstance. http://www.mouser.com/pdfdocs/alphawire-Understanding-Shielded-Cable.pdf
Yeah it looks like gman's right, you are only supposed to ground one end. It says in his link, "Ground the cable at one end. This eliminates the potential for noise inducing ground loops." I'm going to have to fix this in my portable! Maybe it will improve my video quality :)

Edit: @jefflongo , gmans link also explains types of shielding, and the stuff you are using right now probably won't work too well (As you seem to have a experienced). You will want to find some with the copper wire wrapped around the video line.
 

ShockSlayer

the real
.
.
Joined
Jan 16, 2016
Messages
1,512
Likes
3,940
Location
standing up
Portables
please do not ask!!!! I will NOT respond
Yeah pretty sure that's a completely different context; I've dealt with ground loops before and this isn't it. Just think of it like a normal AV cable: ground is connected on both the RCA plugs and the multiAV plug.

Connecting it at both ends gives it a proper return path. Signals like return paths. Don't run any extra unneeded GND wires either, if your only GND connections to the screen/GC/regulators are through the shielded wires, you'll be in good shape.
 
Joined
Apr 29, 2016
Messages
83
Likes
100
What they are missing is that having both ends of the shielding soldered to ground also increases the number of ground connections between each board which in turn helps with interference. This is exactly why many consumer A/V cables have shielding soldered to the sleeves of each plug despite having ground connections on the pinout.

My advice? Give it a try with both ends soldered. If that doesn't work, shield the power lines.


Yeah pretty sure that's a completely different context; I've dealt with ground loops before and this isn't it. Just think of it like a normal AV cable: ground is connected on both the RCA plugs and the multiAV plug.

Connecting it at both ends gives it a proper return path. Signals like return paths. Don't run any extra unneeded GND wires either, if your only GND connections to the screen/GC/regulators are through the shielded wires, you'll be in good shape.
Bingo, but hey, what do we know?
 

Madmorda

Painting Queen
.
.
Joined
Oct 27, 2016
Messages
725
Likes
1,718
Location
Texas
Portables
2
It seems like most ppl online say to only ground at one end, although they do seem to be talking about different applications.

That said, I just checked with my multimeter and when plugging the wii into our LCD screens using official cables, both ends are definitely grounded. I can't crack open my real tv to prove that the ground on AV cables actually is connected to ground inside it, but I'd put money on it.

Bottom line, if it's good enough for Nintendo, it's good enough for me.
 
Top