Video Cable Shielding (how to reduce "noise")

[Tchay]

http://en.wikipedia.org/wiki/Shielded_cable

No this isn't a guide. Rather, I was hoping some of youashen could give me some input on shielding and how to utilize it.

It remains a mystery to me, what exactly will reduce static and "noise" on my 5" LCD screen when using progressive scan. Sometimes it seems to be grounding, sometimes noise to the capacitors of the component chip, and other times something different entirely.

I don't want to call my GCP complete until I get the picture quality perfect. I am using shielded cable for my R,G,B lines. A shielded cable for component. BUT normal wires for V and H sync. I relocated the 3 capacitors of the component chip.

I want to know how to make a shield around the component chip, the AV chip, and the video board points of the 5" LCD screen. I tried using aluminum foil and covering it with tape and wrapping it around the components, but that does nothing. I'm pretty sure a true shield must be grounded, but its impossible to solder to aluminum foil.

Sorry to ramble, but I think this an new topic that is relevant to pretty much every portablizer.

 

[megalomaniac]

previously i informed you i was not having any signal issues...
well as time went on and i moved a lot of things around here i started seeing some of the issues you described..
i was getting a little bit of noise with YPBPR signal but i think it was due to the breadboard setup i was using..(it turned into a mess)
now that ive made a dev board, all signal comes thru clean again..no shielding

ill be doing further testing of the chip for RGBhv vs YPBPR..
maybe ill see something different once i try RGBhv
until i do some testing, maybe you can provide some info to help my testing process:

1. whats your VGA connector wiring configuration?
2. have you tried another monitor? (RGBhv with PSone or PC monitor)
3. have you tried a TV? (YPBPR)
4. if you did try these, was portable monitor connected to power and also on?
5. can you disconnect the portable monitor and try video out to another monitor? ( or provide separate isolated power supply to portable monitor)

 

[public-pervert]

your shield around the video chips need to be grounded. already you did that?

 

[Tchay]

previously i informed you i was not having any signal issues...
well as time went on and i moved a lot of things around here i started seeing some of the issues you described..
i was getting a little bit of noise with YPBPR signal but i think it was due to the breadboard setup i was using..(it turned into a mess)
now that ive made a dev board, all signal comes thru clean again..no shielding

ill be doing further testing of the chip for RGBhv vs YPBPR..
maybe ill see something different once i try RGBhv
until i do some testing, maybe you can provide some info to help my testing process:

1. whats your VGA connector wiring configuration?
2. have you tried another monitor? (RGBhv with PSone or PC monitor)
3. have you tried a TV? (YPBPR)
4. if you did try these, was portable monitor connected to power and also on?
5. can you disconnect the portable monitor and try video out to another monitor? ( or provide separate isolated power supply to portable monitor)

1. I have the component cable stripped of its original shielding. I have 4" of IDE cable going to the motherboard (its 19 or 20 connections total), then I have R,G,B going to their respective points on the video board of the LCD module, but they are shielded. Then I have H and V sync going to their spots of the video board, not shielded. The 3 capacitors are relocated with thin IDE cable (about 1" length) and are not shielded. I noticed the interference going away as I moved the capacitors away from the motherboard and power lines. The component chip has been grounded a lot. ALSO, whenever I use the controller, or sounds are made, I get noticeable interference.

2. I have not. I don't have an HD TV or anything to use unfortunately.
3. I haven't tried a TV, only TV I have accepts composite only.
4.
5. I can certainly wire the component chip to another monitor. Would I be able to use a computer monitor???

I still feel like its something to do with power, ground, or a noise issue. Since its a tiny portable, all my power lines and ground lines are VERY close to these video wires. They are all squished next to eachother.

 

[bud]

You could try putting a toroid and a diode on the screen's power line. It worked when I built that PMP. If you need so more info, there's a few posts about it in my exclusive projekt thread.

 

[ShockSlayer]

^That has worked for me a few times, but you can't beat shielded wire. Might help though, try it.

All signal wires going to the screen should be shielded.
All shields should be connected to ground.
Heck, shield your power wires too. Pretty much ANYTHING going to the screen would benefit from shielding.

Just because you can't solder to aluminum doesn't mean you can't make a connection. Also you can solder to aluminum, I've done it. Just sand it a bit or somethin'. Worst case scenario, just spread out the wire and pinch it, then tape that Sega. The aluminum sheet was an invention I came up with back during the GCP2. It's best application is used as a last resort.

Also, make sure you use GOOD shielded wire. Not thin stuff, usually official A/V cables have good flax.
And even though it's shielded, still keep it off power lines and fan lines and high interference stuff. Oh, and audio amp lines too.

I want a nice clear video of the problem, too, so we can make sure it's actually interference.

Do some other general trouble shooting, don't use batteries, use the 12v AC adapter. Some of what you are saying sounds like the screen's not getting enough power; I've had similar symptoms with PSOne screens as the battery was approaching critical.
Also, shorten those relocated caps as much as you possibly can, sounds like your onto something there. Play around with moving things.

SS

 

[megalomaniac]

The reason for asked trying with another monitor or to supply an isolated power to the monitor is because i dont think shielding is the problem.



for those who have not seen my pic at the GCforever thread, take note:
no shielding
no quality cables
no batteries <---
no cut/modified board <---

the MX chip is completely removed from the official GC cable and all related board circuitry recreated on breadboard.
by the looks of the setup, this should be more susceptible to video interference based on ugly looks...
yet no real video issues have developed which were not caused by common breadboard dev (readjust jumper cables, move a cap little to the left/right, talk dirty to it, etc, etc)
since i am using an AC adapter and uncut board, i can only think the audio and controller contributing to interference sounds more like the mainboard itself injecting noise into the video chip rather than the video chip itself or video chip shielding.

 

[ShockSlayer]

Yeah, that makes sense, but he's got power wires running right up up against his signal lines, which is a big no-no. I don't see anything of the sort on yours, it's all long and in the open, but trust me when I say that power lines can cause a heck of a lot of interference even just close.

SS

 

[Ashen]

Yea, I seem to have issues like this EVERY time I go to close up a portable. Things seem to work fine until everything is crammed together. My issues usually seem to be with video wires being too close to power wires. Try moving your video wires as far away from other stuff as possible. Especially power wires. Shielded cables will only help so much.

 

[Tchay]

Lots of good tips guys. Too late to work on it tonight (roommates asleep) but I will knock this sucker out tomorrow.

Due to my setup, I HAVE to have power lines running through some of the capacitors of the video controller board. Now I don't think they are an issue to the video board as I have ALMOST gotten rid of interference sometimes from moving other stuff around.

I am going to use shield for H and V sync. Then I will use shield for the screens power line. I don't think I can shield the mobo power lines as I'm not sure I have anything thick enough for the current, and some of them are glued/sealed in. It would be a PAIN to redo them, if you know what I mean.

I will also shield the component chip's power line. SS, I tried sanding the aluminum and it got very flimsy and solder still wouldn't stick. But I might try your taping idea. I just want to cover up some areas. After reading up on "noise" it makes total sense that my video is slightly borked. I'm surprised its not worse now that I think about it.

Oh and SS, I've started making screw posts and it looks like I should be able to close up the unit without any gaps

ALSO, I'm ganna hit up Daftmike. He'll know what needs to be done.

EDIT: @megalomaniac, NICE breadboard setup! Stick around. Modretro could really use you

 

[Tchay]

Okay! So I made some aluminum shields (SS, turns out that althoug solder wont stick by itself, with a wire and solder it will stick). Then I fixed up some other stuff, but what really fixed the problem was the H and V sync. After I used shielded cable for those two lines, the noise was barely noticeable. Then I shielded the caps and I honestly can't see any noise.

I have some toroids in the mail, but I have NO ROOM WHATSOEVER to put them anywhere. I have truly optimized every milimeter of space in this case.

thx for the help everyone!

 

[ShockSlayer]

When in doubt, shield it out.

SS

 

[Ashen]

Awesome man, close that Sega up!