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RF Interference on Composite modded 2600? Homebrews only


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#21 Atarileaf

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Posted 12 May 2018 - 09:35 PM

Thanks again for the replies. I did try different power adapters with no change and the 7805 was replaced by the AA modder. I was wondering if it could even be the big 2200UF cap or the green chicklet cap being the issue. Strong enough for regular carts but some more demanding homebrews causing a strain? He said he only replaced the 7805 and cleaned the power and a couple other switches. I do wish I had the rf shield to at least try putting that back to see if it makes a difference. I don't have an extra one for a vader but I do have a heavy sixer rf shield. I know it won't fit but I wonder if just to test, I place the top part of the shield over the IC chips to see if it makes a difference, or is that crazy?

 

I'll try removing the glue tomorrow and take a look at of the underneath of the perf board, see if there's any bad solder joints and report back.


Edited by Atarileaf, 12 May 2018 - 09:40 PM.


#22 CrossBow

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Posted 12 May 2018 - 09:45 PM

Well..now see the original 7805 is only a .5amp rated regulator because that was all that was needed. If you add components to a console, it will draw and require more current to provide it all the juice it needs. This is why I advise that any modded 2600 and 7800 have their 7805s replaced with higher current versions of at least 1amp. It might be I've not seen of these issues because I use my 7800 for all my 2600 and 7800 game playing, but it could also be because I've replaced out the 7805 with a 1amp dc-dc converter to provide better regulated power.


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#23 Atarileaf

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Posted 13 May 2018 - 07:02 AM

 Is it common knowledge to swap out a stock 7805 with a more robust version when modding? If so I didn't know and haven't read anything about it in the modding guides I've been reading. I'll ask the modder if it was 1amp or not, if not I'll swap it out. I know the refresh kits console5 sells include 1amp versions and I have one or two of those kits here.

 

On a different note, going though the forums here I saw Osgelds sale post about his modded systems for sale (I was originally going to buy his but he doesn't ship to Canada) Anyway this line in his sale post caught my eye:

 

Removed RF modulator and installed composite video mod featuring a FMS636x video buffer/driver/filter

 

 

It got me wondering if this filter is something I should look at as a possibility to solve my issue because I'm sure my mod doesn't have one.


Edited by Atarileaf, 13 May 2018 - 08:08 AM.


#24 CrossBow

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Posted 13 May 2018 - 10:49 AM

Very possible. Osgeld is basically installing a board that has a completely different encoder on it for the video. So it takes the signals from the TIA and then puts them through his buffer instead and then you get nice video. So I'm sure his mod board setup doesn't have this interference. 

 

I'm not sure the costs of Osgeld's modded 2600s, but a UAV only costs about $25 shipped and I know it produces excellent results as well. Additionally, you have the output jacks already in place on that 2600, So with the UAV you would only have to solder maybe a few more wires off the 2600 to the UAV and then solder the current wires off your RCA jacks to the UAV as well.

 

It is too bad you are in Canada because I'd be happy to look at it for you and see if I can clean it up or even offer a UAV install replacement on it for you. But as you said, you are in Canada and the shipping would likely be pretty scary to say the least. 

 

I'm located in the middle of the US and shipping a 7800 in a good sized box to ensure it is well protected costs me from $23 - $28 USD as it is...


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#25 Atarileaf

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Posted 13 May 2018 - 11:18 AM

Thanks Crossbow I really appreciate the offer and you're right shipping would be crazy. I also agree a UAV is the way I'll probably go if I can't get this sorted. Is the UAV the one where you solder wires directly to the pins on the TIA? This Vader is one of the ones that has a resistor between two pins of the TIA to bump up the color, something I only discovered yesterday evening.



#26 RickR

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Posted 13 May 2018 - 11:36 AM

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? 



#27 CrossBow

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Posted 13 May 2018 - 04:04 PM

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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#28 Atarileaf

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Posted 13 May 2018 - 05:28 PM

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

Attached Thumbnails

  • 20180513_172215.jpg
  • 20180513_172342.jpg


#29 RickR

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Posted 13 May 2018 - 06:24 PM

A little bit too heavily applied.

 

Now that you have that thing loose...do you get any change in the interference if you move the little board around?



#30 Atarileaf

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Posted 13 May 2018 - 08:03 PM

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

 

 

 



#31 CrossBow

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Posted 14 May 2018 - 06:44 PM

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.


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#32 Atarileaf

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Posted 14 May 2018 - 08:15 PM

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.



#33 RickR

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Posted 14 May 2018 - 08:18 PM

I agree, it's the ground.  And your arm isn't that hairy :)

 

My mod board connects to ground at the very first pin of the RF board. 



#34 Atarileaf

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Posted 14 May 2018 - 09:08 PM

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, 14 May 2018 - 09:10 PM.


#35 RickR

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Posted 14 May 2018 - 09:39 PM

The mod board I like to use looks like this:

 

Atari 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.  

 

 


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#36 Atarileaf

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Posted 15 May 2018 - 05:10 AM

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?



#37 CrossBow

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Posted 17 May 2018 - 03:52 PM

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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#38 Atarileaf

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Posted 17 May 2018 - 05:48 PM

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. 



#39 kamakazi20012

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Posted 17 June 2018 - 01:05 AM

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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#40 Atarileaf

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Posted 17 June 2018 - 07:26 AM

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, 17 June 2018 - 07:28 AM.

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