Wavy Interference in Xbox RGB

[RARusk]

When I got my Xbox several months ago, I managed to get 15Khz RGB out of it for use with my RGB box. I made up a cable and hooked everything up. But when I turned it on, I noticed some wavy interference that "grunged" up the picture a little. I had a newer board revision of the Xbox and thought that this was due to the new video chip inside. I managed to tweak the picture to get rid of some of it but not all. I just resigned myself that this was a problem that I may not be able to fix.

At this point I am working on a Component to RGB converter box that will autosync between 15Khz and 31Khz. This box, like my RGB box, gets its power from the console unit using the +5VDC pin within the A/V port of the console. But some of the chips require -5VDC and I found a Negative Voltage Generator design (using the 555 timer chip) to try to get it. When I put the Generator together and added the +5VDC from the Xbox, I would get a lot of interference. Thinking that it was the Generator design itself, I hooked up the converter prototype to a PC digital switching no-load power supply that I got at a local electronics store. I put in ground and +5 from the supply and turned the Xbox on.

The power supply worked and worked quite well. But when I got a stable enough picture, I noticed that the wavy interference (that had also appeared while prototyping the converter) was gone. I then took apart my RGB box, disconnected the +5VDC line that went to the game console, and hooked up the power supply. Then I hooked up the Xbox and turned everything on.

The RGB came up as clean and pristene as I wanted it. The realization then hit me that the wavy interference wasn't due to the new video chip, it was due to the Xbox internal power supply. The +5VDC I was using from the Xbox was very "dirty". This could also explain the problems that the X2VGA box has been having with some of the Xboxes. That device gets it's power from the Xbox just like my projects and it must be dealing with the same interference.

Of course, I have one fix which is my external power supply. But the more optimal solution is to open up the Xbox and fix the internal power supply unit. Can you imagine what this "dirty" power is doing to the rest of the Xbox's internal components? Is there any leads on how to fix the internal power supply within the Xbox so I can clean up the power?

[benzaldehyde]

Greatest discoveries in human history:

1. Fire
2. Agriculture
3. RARusk figuring out what causes the shimmering on newer consoles (or is this something else?).

:lol:

[Darklegion]

I'm guessing that the the shimmering may be caused by the flicker filters in modern consoles,which try and eliminate the flickering effect on high-res,interlaced images.Older consoles didn't use flicker filters and most games weren't high-res,and thus didn't flicker either so there was rarely any need for a flicker filter.Thats just a guess of course,it could be any number of reasons...or just that newer consoles are just made like shite....which they are :rolleyes:  

[RARusk]

In the case of the Xbox it is the +5VDC pin that is causing the interference. I went back and looked through the X2VGA and VD-Z3 threads. Benzaldehyde has both units and posted his findings. His X2VGA had a shimmering problem so he got the VD-Z3. That had no problems at all when he hooked it up. The difference? The VD-Z3 had it's own external power supply and the X2VGA did not. The X2VGA uses the power from the Xbox to power it. Benzaldehyde also noticed that when he used the X2VGA on a friend's Xbox (which was one of the older versions) it had no problems.

When MicroSoft did the latest version of the Xbox motherboard, they messed up the internal power supply. I would like to fix it since that would be the best way to solve the problem. It would save additional wear and tear on the motherboard since the chips don't like "dirty" power.

I've since added a power cord to my RGB box and hooked up a simple plug to the necessary wires sticking out from my power supply so I can hook my box up the power supply unit. It works great. I'll try to post pictures later.

If you were to hack the X2VGA and hook it up to an external power supply it would work great on ANY Xbox not just the older ones. Hell, I would hack it and get it to work on my PS2 also. Just a matter of cabling.

If there is any other similar shimmering problem on any other console you may want to take a good look at the internal power supply before you start looking at the video chips.

[benzaldehyde]

I should note that I worked with Neoya (if by "working with" I can mean "sent them my XBox and X2VGA for their experimentation") and they were able to correct the problem in the X2VGA. They sent it back and it works just as well as the VD-Z3 now. I'm not sure what they did, but because of my help, I'm sure I could ask. I'll see if I can beat some info out of them.

[RARusk]

Hmmm......very interesting. It would be nice to know how they fixed the problem for the X2VGA+. They must have added some sort of filter for the +5VDC to correct the problem. That would be nice to know.

Below is a picture of my RGB box. The silver box at the top is the power supply. The power supply connection to the RGB box is between the supply and the box. To the left is the detachable RGB cable for my Xbox. The new power cord enters just underneath the connection port. To the right is my monitor and audio plugs.

The case used to be a NAKI Dreamcast VGA case. I grafted a part of a Xbox A/V video box (which has the monitor and audio plugs) on the back. I grafted a 9-pin plug holder on the front side and I use 9-pin plugs for my customized RGB cables. The panels on the sides cover up the cable hole (from the Dreamcast cable). It also has about four layers of flat black model paint to give it it's color.

Inside is a EL1883 sync separation chip and a Sony CXA-1145 RGB chip (wired for amplification).

All in all it serves me well and now I've made it much better with the external power supply.

[RARusk]

Bleh! That picture looked better when I still had it on my Mac. Here's a brighter picture.....

[Endymion]

Bleh! That picture looked better when I still had it on my Mac. Here's a brighter picture.....

That's funny, the first one still looks pretty dark on my Mac.

[atom]

Hi, this is whats happening to your rgb signal. When you run +Volts parallel with a signal line, electrons will jump from the power line to the signal line. This is where shielding comes in. Shielding is pretty much impractical for homemade cables, it is more practical to get power from another source as you did. If you do shield your cables, connect the shield to the ground on the xbox side only. When doing so the shielding will catch the electrons and return to the console.

Also, running power lines perp to signals will take care of the problem, again not practical.

[RARusk]

Interesting. So the problem could possibly be traced to how the newer Xboxes handle ground and ground shielding. I should point out though that I've never had a problem, until now, using the +5VDC from any of the consoles that have ever been hooked up to the box. And I have quite a few. Plus the older Xboxes don't seem to have a problem.

Still, that is very good information. Benzaldehyde said he would try to find out how Neoya fixed the X2VGA+ to get around this problem. Should be interesting if he manages to get the info. Would be very helpful for homebrew projects.

[Darklegion]

I found a great technical article on epanorama.net for everything on grounding shiielding,EMI etc http://www.engineeringharmonics.com/papers/s_vc.htm

[RARusk]

Today I decided to remove most of the wires hanging out of my power supply. Although the +5Vsb line works fine, I can't seem to get the rest of the voltages working (even with a power resistor to create a dummy load - this may be why it had a $2 price tag at the electronics store). So I opened it up to clip the wires away except for the one line that was working. In the process I noticed a switch that I hadn't see before and I decided to plug in the power cord while it was open.

Then came a "pop" and this resulted in me being the proud owner of a dead power supply / paperweight / handy hand-thrown projectile weapon.  

So I reopened my RGB box and restablished the power line to the console.  For now I will have to put up with the "grunge" on my Xbox until I can get a replacement power supply box.

Does anybody know if someone makes a no-load power supply for homebrew devices? Something like a small compact box with a plug that has all of the voltages (positive and negative - max load of about 500Ma) you will need (or want).

I'll continue to play with PC power supplies though. I got good results using my RGB box with one until I fragged the power supply. Just gotta be a little more careful.....

[Darklegion]

Could you take a picture of this effect? My xbox is a 1.4 with a 1.1 power supply and I would like to know what to look for when I get RGB sorted  out and working...as if it doesn't exhibit the effect then most likely you are right about it being the power supply.....unless of course it happens on the mobo side rather than on the PSU.I seem to be getting wavy interference at the moment anyway but it is most likely caused by something else in my case and it is fairly extreme....

[RARusk]

I tried taking a picture of the interference but it wouldn't show up on the digital camera. The interference is just shifting wavy lines on the screen. The problem shows up when using the +5VDC line from the A/V plug so if you are hooking it up directly to a monitor that uses Composite Sync (like a Commodore 1084) then you should have no problems regardless of motherboard revision.

My RGB box uses a sync chip and an amplifier so I use the power from the console unit it is attached to (for now) and therefore I have to work around this annoyance.

[Darkman]

Now that's an interesting thread. Even though I don't have an XBox, I will express my observations with other consoles. I think it must be the power supply, or more precisely - the fact that it is internal. My Dreamcast shows significant interference while my PSone and Gamecube do not. Maybe that has to do with their power supplies being external? Or maybe I'm just talking out of my ass...

[benzaldehyde]

Well, I'm not so sure about that. The Saturn and PSOriginal have no such issues, and neither did my XBox until I tried using the RGB cable with my new XBox (I was kicked off the monitor by my brother playing Skies of Arcadia). Now I see; there is some powerful interference, not just the shimmering. I'll write to Neoya as soon as possible about it.

[RARusk]

Having the power supply internal seems to have little to do with the interference. I own a PS1, PS2, Sega Dreamcast, and an Xbox which all have internal power supplies. I have never had any interference from any of those except from the Xbox. I should also note that, based on some information from Neoya's web site, that this problem seems to occur on the newer motherboard revisions of the Xbox. Older Xbox's don't seem to have this problem. This was verified by benzaldehyde when he took his X2VGA to a friend's Xbox which was one of the older models.

When MicroSoft did the motherboard revision, they also redid the power supply. Probably an attempt to reduce the cost of building the console.

One of the members of the user group I attend suggested a filtering capacitor on the +5VDC line from the Xbox. I got several types (and ratings) of capacitors and tried running the +5 through them. No dice. But I wouldn't be suprised if that is what Neoya did on their X2VGA+ which is supposed to have solved this problem.

If Neoya isn't forthcoming with their solution may I suggest to benzaldehyde that he open up the X2VGA+ and take a picture of the motherboard (especially near the +5VDC line) so we can examine it and see what they have done - if that can be done of course.

By the way, I got another switching power supply and hooked up the +5VDCsb line to the RGB box so my RGB from the Xbox is clean again.  

Now I need to learn to do a proper dummy load so I can get the rest of the power supply working so I can move forward with my converter project.....

[Darklegion]

Neoya seem to have  a problem with the public knowing anything about the internals.They even said a while back that they don't want any pictures of the internals posted on the web.Benzaldehyde should take some good high-res photos of it,and Lawrence can post them all over gamesx
I really do not like manufacturers who are arseholes to the hardware hackers,particularly the ones that scratch off the tops of their chips.

[atom]

Why are you killing yourself over this? Yes, its the power supply. The 5v that is going through the line is static-ee and you need to filter that out. Did you make the cable? If you did, shield the 5v line in the cable. You can even use tinfoil if you need to, just wrap around and make sure you ground it. Just shield the 5v not the whole cable.

If that doesnt work, then... buy a gamecube!

[Aidan]

Shielding the 5V line isn't going to help if the power supply behind the 5v line itself is the cause of the interference. Cleaning up the 5V line with an inductor and capacitor would help reject the interference at the adapter end, in a low pass filter configuration. Guesstimate the lowest frequency of the interference, and then tune up the LC circuit to reject it.

[Aidan]

I'll continue to play with PC power supplies though. I got good results using my RGB box with one until I fragged the power supply.

At a guess you must be on 220 or 240V then? If that's the case, you may just have blown the fuse when you reconfigured the PSU to accept 110V If there's no sign of damage to either the bridge rectifier or the big capacitors, then it might well still be ok, other than the dead fuse.

[RARusk]

Aidan's right about the inductor fix. I used a ferrite device to clean up the interference. More detailed info in my "Wavy Interference Fix for Xbox RGB" topic.