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RF Interference on Composite modded 2600? Homebrews only


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#1 Atarileaf

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Posted 07 May 2018 - 05:40 AM

I posted this on Atariage but I thought I'd try here too.

 

I purchased a modded Vader from a user who I've bought other things from before and he seemed to know his stuff and in fact this system does work very well and gives a nice picture on normal carts - except for one odd issue - some of my homebrew carts seem to give off what I can only describe as RF interference which seems impossible since the RF modulator has been removed. It only happens with some homebrews and not others and I'm assuming has something to do with the extra tech or lack of shielding in either those carts or on the board itself. Draconian, Lady Bug and Fall Down are the worst offenders but Space Rocks, Juno First and Colony 7 are fine.

 

Is there anything I can do to fix this situation? Pics below

 

draconian interference.jpg

 

draconian interference mod.jpg



#2 RickR

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Posted 07 May 2018 - 09:42 AM

My first suggestion would be to try a different composite cable-set.

That is a weird one. Please let us know if you solve it.
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#3 CrossBow

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Posted 07 May 2018 - 05:46 PM

Since you said it only happens on some homebrews, I'm inclined to agree with your guess about the lack of shielding inside the homebrew carts. Could be they are picking up something in the RF range that is causing the video interference. 

 

have you tried to move the console around or perhaps other crazy stuff like tilt it on its side with a game in it and such to see if you can make those lines more around and change? If you can, that confirms it is outside RF causing an issue.

 

Also was the RF shield removed from the 2600 when it was modded? I always..ALWAYS tried to keep the RF shield in place as the RF modulator isn't the only thing to get affected by unwanted RF noise. Even the newer mod boards can be affected by outside RF radiation.

 

Although we don't use analog over the air signals anymore or RF modulators, we actually use more RF in the world today and all around us than we ever have before. Bluetooth, your Wi-Fi in your house..etc..all exist in the RF ranges. Even your cell phone, that is why we had to get rid of the old analog signals, because we needed them for other stuff. It is also why many of the older consoles tend to look even more on modern displays. Newer displays do NOT have the filters and such in them that our old TVs did to help filter that crap out of the video signal.


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#4 Atarileaf

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Posted 07 May 2018 - 06:19 PM

Thanks guys, different cables didn't make any difference and the rf modulator was removed by the AA user from whom I bought this unit and the RF pattern does move so it's not static lines but moving the console around doesn't seem to have any effect but since the lines are always in motion I'm not absolutely certain that's true.

 

Another user on AA said a couple of resistors should have been removed to improve the video but he never said which ones and I'm not sure if that in itself would solve an RF bleed issue

 

Is there a way to shield the mod somehow or would that not have any effect. 


Edited by Atarileaf, 07 May 2018 - 06:25 PM.


#5 CrossBow

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Posted 07 May 2018 - 06:41 PM

Well..when I mod consoles, I try and put the mod boards within the original confines of the logic. Thereby they are able to be covered in the original RF shield that the system came in. Now having said that, I've also heard some people state that an AV mod looked better when they put the RF shielding on the system but put the AV mod board outside of the shielding. Again, if you can move the system around and the interference pattern changes in the process, that is definitely interference causing it. Only other way to try and shield the mod board if you haven't the original RF in place, would be to add wire and move it so that it sits under the main pcb. At least that way, you are shielding it by using the main pcb as the shield itself. 

 

Also take some foil and lightly wrap it around the cart to see if that helps. If so, that indicates the issue is the lack of shielding on the homebrew carts. 


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#6 Atarileaf

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Posted 07 May 2018 - 08:09 PM

The tin foil trick didn't work but when I was touching two of the wires and held them in my fingers just so the picture cleared up. The one wire is what I'm assuming is the ground as it's just soldered to that metal strip on the board and the second wire is the video wire that goes to the yellow composite out. It's attached to the top middle portion of the little mod breadboard. Those two wires moved just so clears up the picture. This would explain why when I first got the console Draconian looked fine. It was only because I had to open the console to do a slight adjustment on the color pot (fast foods purple pickles were blue) and then put it back together that I noticed some homebrews were showing this interference. I must have moved the very tenuous wire configuration to cause the problem 

 

All three gray wires are very thin and fragile looking and are tied together with what looks like a small green zip tie. Should these wires not be tied together like this? Are the wires themselves incorrect for this type of mod?


Edited by Atarileaf, 07 May 2018 - 08:09 PM.


#7 Atarileaf

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Posted 08 May 2018 - 07:07 AM

I'll try to post some video of what I'm talking about since it's hard to explain. Probably won't be until tomorrow though. Seeing Infinity War for the first time tonight :)



#8 CrossBow

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Posted 08 May 2018 - 10:15 AM

My first guess is that the ground itself isn't making a good connection. you said if you press on them just right, the picture clears up? As for them being zip tied together, that isn't an issue and is good that they were trying to keep them nice and tidy. 

 

I'm thinking the video out wire on the top center of the perfboard might not be making a good connection and this is why when you held it just so, the picture cleared up. Try just moving that one around a bit and see if it helps? If it does, then that wire needs to be hit with some more solder and heat most likely to secure it in place on the perf board better.


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#9 RickR

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Posted 08 May 2018 - 10:32 AM

I agree with CrossBow.  No offense meant to whoever did the mod. (I really dislike when people get super nitpicky about these mods). 

 

I think the most critical part of the mod is the ground wire that goes from the mod board to all three video/audo jacks.  I like to use as thick a wire as possible for that....and solid core. 

 

See if this helps:  unplug one or both audio jacks from the console and see if that fixes the interference. If yes, then that ground wire is probably loose at one of the solder points on the jacks. 


Edited by RickR, 08 May 2018 - 10:34 AM.

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#10 Atarileaf

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Posted 08 May 2018 - 02:34 PM

Thanks again for the advice guys I'll try those to.orrow night and report back

#11 kamakazi20012

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Posted 10 May 2018 - 04:28 PM

I did one of these mods for StormSurge last year, but the mod was a bit different and used thick wiring. if I remember correctly, I had to remove a resistor along with the transistor. I know mods vary but if I can find that manual you might try removing a resistor.

I agree with others...the RF shield should have stayed. It doesn't take much to interfere with a VCS signal. Try a different power outlet as well that is not shared with any high power devices like a TV or A/C unit. Lamps can mess with them as well.
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#12 Atarileaf

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Posted 10 May 2018 - 05:18 PM

Thanks I will try that. Hopefully tomorrow night. I was supposed to work on it a couple nights ago but I've been swamped with work and other family responsibilities that's kept me from working on the mod. I still want to post a video of what it's doing when I fiddle with the wires and show the solder points better


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#13 CrossBow

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Posted 10 May 2018 - 05:52 PM

Again the fact that the image changes at all when you touch or move the wires, is sure proof there is a loose connection. Or..worse...there could be a break in the wiring within the insulation itself. But i'm inclined to think that one of the connections and most likely the video connection on the perfboard is the one to be looking at first.

 

I do use solid core wire...sometimes. But if you plan to service the system much in the future, then it is best to use a larger gauge stranded copper wire instead to give yourself more flexibility. Or...like I do, I actually use header pins and connectors so that I can quickly unplug stuff to work on it. Because of that, I do use thin solid core kynar wire for connections that won't need to be moved around, and always make sure that my power and ground wire is thick gauge for best connections. Also important to run the video and power separate if at all possible in that I keep their wiring away from each other to prevent any noise that way. Although it isn't such an issue with DC voltages like it would be with AC voltage. That is the other reason I try and attach my video ground off the same gound as the TIA. If you just use the ground around the edge of the PCB, you do stand a risk of some non filtered noise running along that plane. Also not a bad idea to keep the ground separate from the audio and video since the audio actually uses AC voltage signals. 

 

The other more expensive option (and the one I would actually choose...) would be to rip that out and install a UAV in it instead.


Edited by CrossBow, 10 May 2018 - 05:56 PM.

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#14 Atarileaf

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Posted 10 May 2018 - 06:28 PM

Thanks crossbow. I gotta leave but here are a couple quick pics. The perf board is glued down so it may be hard to access without doing more damage. The other pic is the 3 composite connectors and the way they are soldered

Attached Thumbnails

  • 20180510_182344.jpg
  • 20180510_182139.jpg

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#15 Atarileaf

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Posted 11 May 2018 - 07:23 PM

Well I removed the little ties holding all 3 wires together and moved the ground and video wire as far away from each other as possible but it made no difference. I guess i should try replacing the video wire and finding a thicker wire somewhere. I assume I'll have to pry the perf board off so i can get underneath it. I'm stumped with this as I've never dealt with mods before and the reason I bought a modded system was because I'm not comfortable with that level of solder work yet. 

 

If there's a manual for this mod out there I'd appreciate being directed to it.



#16 Atarileaf

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Posted 12 May 2018 - 08:18 AM

I found these instructions online - http://www.coolretro...ation_Guide.pdf

 

So first I'm going to remove the two resistors it mentions to remove to see if that does anthing - R209 and Q202

 

If that doesn't work I'm going to replace that wire that runs from the perf board to the yellow composite and hope that does the trick.

 

Problem is, what kind of wire? I don't think I just have wire laying around the house. If I buy some, Console5 sells it but it doesn't look any thicker or more insulated than what's already in there. In fact the person who installed this mod might have bought his wire from them - https://console5.com...0cm-length.html


Edited by Atarileaf, 12 May 2018 - 08:25 AM.


#17 Atarileaf

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Posted 12 May 2018 - 09:14 AM

Removing the resisitor had not effect. Q202 was already removed, I just removed R209. I guess I have to source some wire



#18 Atarileaf

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Posted 12 May 2018 - 02:30 PM

Might all be a moot point. The perf board is hot glued to the motherboard and I was able to cut it off the atari board fine but to get the glue off the underside of the perf board is impossible without destroying it. I may just live with it as is and chalk it up to a learning experience. The mod is fine with normal games but these unshielded homebrews are giving it a fit. Which is a shame since homebrews are what I play the most.



#19 CrossBow

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Posted 12 May 2018 - 07:33 PM

If the glue is in fact hot glue...then you only need to use Alcohol and it will soften the hot glue and allow you essentially just peel it off he boad. But you really have to saturate it in there and make sure it seeps in under the glue.

 

As for the kind of wire, I also use basically the same kind of wire. I don't think the wire is to blame so much as a loose solder connection or possibly a break in the wiring that can't be seen within the insulation.


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#20 RickR

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Posted 12 May 2018 - 09:12 PM

I also wonder if it may be the power adapter or the 7805 regulator/transformer.  Do you have a different power adapter to try? 

I think there has to be a simple fix for this...instead of having to tear it apart and replace wires.  I just feel like it can't be the wires -- if it was, it would pretty much have the issue with all games.  It's gotta be a shielding or power issue. 






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