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Atarileaf

RF Interference on Composite modded 2600? Homebrews only

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Wow, the UAV looks really nice.  Do you happen to know if the wiring gets any easier if you skip the S-Video out and just do composite?  I guess the inputs would all remain the same, just skip the outputs you don't need, eh? 

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Wow, the UAV looks really nice.  Do you happen to know if the wiring gets any easier if you skip the S-Video out and just do composite?  I guess the inputs would all remain the same, just skip the outputs you don't need, eh? 

 

I will be honest and state that I've not installed a UAV onto a 2600 yet. But others have and stated it looks great. As for how much simpler, I'm not entirely sure. I can tell you that the UAV is a replacement encoder, so as such you still have to wire all the needed lines to the UAV board for it to process that video correctly. But yes, if you only need composite output from the UAV, then you would only need two wires from the output side of the UAV. Composite and ground.

 

The UAV does NOT handle audio though, so that has to be done separately. Bryan (Who makes the UAV), also created an audio amp replacement board that is very easy to install. But sadly when I checked with him on this, he stated he didn't have any made up and not making more because I believe he plans to incorporate the audio into the newer revision of UAV he is also working on.

 

I hope that on the resistors you "removed" that didn't completely remove them? All that is needed is to simply cut one of the legs off the resistors to disable them from the circuit. This way if you need them back in place (Like would be needed when putting in other mods that require them or if you wish to take it back to stock condition), then you only have to apply a small dollop of solder to the leg you cut and you have it repaired back in circuit again.

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Ok I got the hot glue off thanks for the tip on that. Here are close up pics of the top and bottom of the little perf board. Does the solder look Ok? Sorry the flash may make it hard to see

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Ok here is some video that will hopefully show you better than I can describe it. It does seem to clear up when held or moved just so. As I mention near the end, I can't tell if it's the board or the wires coming from the old RF connections. Sorry for the hairy arm :D

 

 

 

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Defintely a grounding issue... I can tell from when you are touching the side of it there at the beginning. Or at least that is what it looks like to me.

 

That was the bottom of the perf board I was touching sorry it was probably hard to tell. What would you recommend to grounding it better? It's currently just soldered to a metal strip running along the board.

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Interesting. The ground wire on this runs from that metal strip to the 3 rca plugs. In ones I've seen onnline it goes in from that first rf pin, into the mod board and then out to the rca plugs. The only wire going out from the mod board is the video wire. Was this ground wire installed incorrectly or in the wrong place?

Edited by Atarileaf

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The mod board I like to use looks like this:

 

post-41-0-03686900-1526348243.png

 

And yes...you use ground and power from the RF board pins, and then ground goes out to the jacks from the little board.  

 

PS - one other thing -- when you mentioned you don't have wire.  Do you have a "Harbor Freight Tools" near you?  I'm not sure if they are in Canada or not.  But they sell a variety pack of wire spools in a nice stand for cheap.  

 

 

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The mod board I like to use looks like this:

 

attachicon.gifAtari 2600 mod.png

 

And yes...you use ground and power from the RF board pins, and then ground goes out to the jacks from the little board.  

 

PS - one other thing -- when you mentioned you don't have wire.  Do you have a "Harbor Freight Tools" near you?  I'm not sure if they are in Canada or not.  But they sell a variety pack of wire spools in a nice stand for cheap.  

 

 

 

Thanks for the tip on the wires Rick :)

 

I'm really starting to think this mod isn't installed correctly. I see boards similar to the one you show in this picture and the ground goes both in and out from this little board. Mine just goes in from the first rf pin but that's it. The other ground is soldered from that metal strip to the rca jacks so perhaps the video out wire on the perf board isn't being ground properly on that board? I may order one of these and redo it since it's a similar set up to what I'm already working with and again, the ground goes out from the mod board which I think is what should happen right?

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Basically any circuit requires voltage to operate in most cases, and to get a circuit to be a circuit...you need voltage and ground for it to go to. So yes, most of these mod boards should require a ground signal going into the mod board, and then you can either use that same ground point to go out to the RCAs, or you can ground the RCAs separately to another point along the main PCB.

 

If a mod board has grounds on it, I tend to use them. If it only has the one ground for it self, then I will nearly always separate the ground from the video and audio.

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Basically any circuit requires voltage to operate in most cases, and to get a circuit to be a circuit...you need voltage and ground for it to go to. So yes, most of these mod boards should require a ground signal going into the mod board, and then you can either use that same ground point to go out to the RCAs, or you can ground the RCAs separately to another point along the main PCB.

 

If a mod board has grounds on it, I tend to use them. If it only has the one ground for it self, then I will nearly always separate the ground from the video and audio.

 

Sounds reasonable and I'm guessing normally separating the ground would be fine and indeed it is fine for normal carts but some homebrews seem to be giving this particular set up some fits. I'm hoping that redoing the mod with a board like the one I linked to will help alleviate that difference. 

 

I'm assuming my problem is pretty rare if not completely unique. I don't think I've read of too many having a mod work perfectly fine for normal carts but have an rf interference style seizure when it comes to homebrews. The fact that I can clear up the image by moving the perf board does seem to indicate a grounding issue as you said. I suppose I could try to ground out from this perf board but when I look at the rats nest of solder joints underneath I think the smarter move is to get a new similar board and start from scratch. 

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Wow. You have two grounds going on here which I didn't catch before. The ground signal going to the RCAs on the console should be coming from the ground connection where the RF modulator use to be and not the grounding plane for the RF shielding. Your video is proof that when you are touching the mod circuits that it is using you for a ground source. An RF shield over the board where it is suppose to be would clear most of that up.

 

Also of note...it is a big no-no to run a 2600 without that shield for one reason...static electricity. During a testing phase of the four switch 2600s, Atari discovered that any static discharge from human hands when they touched any of the four metal switches could fry the circuitry inside...namely RIOT, 6502, and/or TIA. There is suppose to be two thin metal strips to avoid static. One thin strip for the POWER and TV TYPE switches and the other for the GAME SELECT and RESET switches. The thin metal foil-like strips have adhesive on the bottoms and grounds those switches to the RF shield. You can still get those new but I am not sure about the shield. I would bet putting those on there would solve this problem.

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I did get in my mod kit from ebay, similar to the one RickR posted a picture of in post 35. I'll install it next weekend when I get time. I didn't think grounding to the metal strip was the way it was supposed to go. I can get an RF shield off another vader I suppose and you're right I should get that metal tape to ground the switches I don't know why they're missing. I'm assuming the person who modded it thought the rf shield wasn't needed anymore. Of course I'd have to remove the current ground since it would be in the way of putting the shield back so the new mod kit is probably the best way to go anyway and I can run the ground from the mod chip as it should be.

Edited by Atarileaf

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You don't need the same exactly stuff as before. All you really need is a decent size piece of wire to solder the outer casing of each switch and then eventually solder that down to the RF ground plain somewhere. But if you really want to use foil tape like before, then you can just buy a small roll of Chrome repair tape from an autoparts store and cut it as needed. It is basically the same stuff.

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Well after several months I finally got around to installing a new mod from ebay. I took the original apart and started from scratch. Unfortunately the problems still persist so it's not the mod itself after all. I'll attach pictures but if you go to the first post you can see the output is the same. Lady bug in particular looks horrible but I had that problem from the beginning even on unmodded systems through RF. It's hard to tell on the Draconian picture but there are wavy lines all through the picture. So should I take an RF shield from another Vader and put it in this one? The original was thrown out by the person I bought the modded system from. Or is there another possible reason for this RF looking interference on a composite modded system.


 


Again this only seems to happen with 3 homebrews - Draconian, LadyBug and Fall Down. 


 


Space Rocks, Juno First, and Colony 7 seem fine and all original games look great too. So other than 3 games this mod seems to work fine. It seems to be a homebrew issue but Al mentioned he's never seen anything like it and considering how many hundreds of homebrews and systems he tests, I trust it's something peculiar to my Vader.


 


PS - This was my first attempt at modding a system myself so other than the original problem being present, I'm pretty proud of myself icon_mrgreen.gif


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I hadn't thought of power...but could be. The original VRs are only like what.. 500ma rated? And that could have been pushing it already to near that limit with all the components installed. Wonder if a newer and higher output 1amp version 7805 would help?

 

Especially when the newer homebrew games also take up some juice to power the additional chips in them that they have. 

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It's a possibility. The AA user who did the original mod did say he replaced the voltage regulator but I don't think he mentioned if it was 500ma or 1amp. I may have some extra's from Console5. I believe these were the ones I bought, I believe they're 1amp https://console5.com/store/7805-5-volt-regulator.html

 

PS - I didn't take a pic but I used strips of that metallic tape and bridged the switches on each side and then from the innermost one to the metal strip that runs along where the rf shield would normally sit. I hope that is sufficient to preventing and static issues. So far so good though.

Edited by Atarileaf

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Yes the metal strips where you placed them should be fine. I still would have tried to solder on some wire instead to make sure it was all grounded properly. I still think part of the issue is that you don't have actual RF shielding on the system anymore. I see this kind of thing even on modded consoles like my Colecovision, Intellivision, and especially the 7800 if I don't find ways to put the RF shielding back on. 

 

And yes I believe console5 only has 1amp and up output VRs that he sells. I bought my 2amp output versions from him last time I believe and that is what I have running in my sega Genesis.

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Also you can literally grab your ground for these AV mods from anywhere. Take any multimeter and you will see that all grounds have continuity with each other in these old systems. So..to make it easier I will usually just find the nearest ground point around the circuit I'm grabbing my signals from to be sure it is proper. In the case of the 7800 UAV mod I use the grounds off the UAV board itself. But honestly you could just grab the ground off of any part of the large ground plane around the main board and attach that to to your RCA connections and be fine.

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Well if I come across any 4 switch parts machines in the future I'll just grab the rf shield out of one of those. Wouldn't I have to cut a slot out of the shield since I'm running one wire soldered to the base of a resistor that sits inside the shield area?

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Yes, you would still need to cut a small notch out of the RF shielding for the audio input wire you have there. (I assume the yellow is audio input since it is tied to two resistors, one for each TIA channel?)

 

Unless there is just enough space to wedge that wire between the audio tuning coil? But you would have to desolder it from the resistors, thread the wire through the RF opening for that coil to come through and then solder it back down. Things like that are why I solder on header connectors to most of the wiring so I can easily take it loose for full disassembly without have to desolder stuff.

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