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AtariLeaf

RF Interference on Composite modded 2600? Homebrews only

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No unfortunately I don't have a spare and the modded system came to me without the rf shield included. I'm assuming because the ground is soldered to the metal strip on the motherboard it would no longer fit?

 

Yeah, you'd have to solder that ground somewhere else or modify the RF shield to fit.

 

..Al

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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 :D

 

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post-2493-0-12110100-1535828270_thumb.jpg

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Yeah, that is strange. It seems your brightness is turned up pretty high, the background for those screens should be black. Is that interference visible if you turn the brightness down? I'm not an electrical engineer so I can't speak to what might be causing this.

 

Of the six games you listed (Draconian, LadyBug, Fall Down, Space Rocks, Juno First, and Colony 7), there are two different boards used between them.

 

Draconian - Melody

Lady Bug - Aria

Fall Down - Aria

Space Rocks - Melody

Juno First - Aria

Colony 7 - Aria

 

That you are getting interference with different games using the same circuit boards is interesting.

 

..Al

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Yeah, that is strange. It seems your brightness is turned up pretty high, the background for those screens should be black. Is that interference visible if you turn the brightness down? I'm not an electrical engineer so I can't speak to what might be causing this.

 

Of the six games you listed (Draconian, LadyBug, Fall Down, Space Rocks, Juno First, and Colony 7), there are two different boards used between them.

 

Draconian - Melody

Lady Bug - Aria

Fall Down - Aria

Space Rocks - Melody

Juno First - Aria

Colony 7 - Aria

 

That you are getting interference with different games using the same circuit boards is interesting.

 

..Al

I turned up the brightness just for the sake of the pictures but yes it's less prominent when I set the brightness to their proper levels.

 

There must be a component on this board that's out of spec but I can't for the life of me think of which one. I know the voltage regulator was replaced but I believe that's it. No caps were replaced as far as I know.

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I got the same as Ladybug shown above on a 2600 I had modded , which I no longer have . It had strange background artifacts when I put in Toyshop Trouble and I think one other game . When I played Omicron , it was so dark you could hardly even see what was going on .

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I think I remember reading comments like yours Brian. I bought Ladybug about 10 years ago so my memories are fuzzy but I do remember hearing similar stories. I think I even started a thread on it at the time. I've come to the conclusion that I can live with it as is. 98% of my collection works fine and I just dial down the brightness on the rest. I mean what am I supposed to do? NOT play Draconian and Lady Bug? Can you even call that living? ;)

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This has come up many times in the past where homebrew games and the Harmony cart cause this interference on certain 2600's. I had the issue on mine and found that there was a capacitor disconnected on my board, but others have had the issue and it wasn't that... I'm not sure it was solved, but there are several threads about it.

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This has come up many times in the past where homebrew games and the Harmony cart cause this interference on certain 2600's. I had the issue on mine and found that there was a capacitor disconnected on my board, but others have had the issue and it wasn't that... I'm not sure it was solved, but there are several threads about it.

 

I have read this on threads in the past but I can't recall exactly what it was. Time for some more research I guess but I'll probably just leave this system as is. As I get more comfy with soldering I'll do more mods on other systems, maybe the UAV mod down the road.

 

If you're positive it's due to the lack of shielding I kinda wonder if the carbon paint I have would solve it, as it claims to be shielding

 

Not positive, but it's a theory that has been postulated in this thread.

Edited by AtariLeaf

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I'll ask the member who sold me the console what the mod was called but the RF is removed completely so there's no chance of stray interference coming from it. I'll try another tv or two tonight, this was one of my Commodore 1702's that I normally use for playing. When I do initial diagnosis for things like his I do usually try other televisions at first but with this only affecting homebrews I didn't think it was necessary but you never know. Could it be a bad cap that causes this? The big 2200uF main cap perhaps?

 

This brings me to my next question - is it possible that with all the new tech in these modern games like Draconian that they're putting some extra strain on the Atari and it affects it like this? I'm no expert so I'm just postulating at this point but other than lack of shielding it's the only difference between a new homebrew and something released in the 70's.

 

Another question - Juno First looks great while Draconian doesn't. What's the differences, board or tech wise, between those two?

 

Juno First runs on the Atari's CPU, the other game runs on the ARM CPU which can cause interference.

 

imo RF is best in any event; a composite mod generally eliminates artifact colors which is unfortunate.

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Juno First runs on the Atari's CPU, the other game runs on the ARM CPU which can cause interference.

 

imo RF is best in any event; a composite mod generally eliminates artifact colors which is unfortunate.

 

Can this cause hardware damaging strain though? It got me thinking that all this extra hardware in these carts that is pushing the CPU too hard, could it actually damage anything on a 2600?

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Can this cause hardware damaging strain though? It got me thinking that all this extra hardware in these carts that is pushing the CPU too hard, could it actually damage anything on a 2600?

 

That's a very good question.

When modern CPU's are under load they generate a stronger magnetic field:

 

https://superuser.com/questions/19968/processor-noise-what-generates-it

 

We can see the bleed, but the stress is within tolerance.

 

I would buy one if there was a run of Harmony carts with tiny Faraday cages around the ARM like old school Televisions have.

 

Something else to consider, how about the cumulative effects from other sources?

 

CF bulbs, microwaves and modern electronics can collectively create enough microcurrent to activate Mr Coffee's microelectric switch which acts like the solenoid when you start your car. Here's an interesting read and a good argument for keeping our old systems unplugged:

 

https://www.aptsources.com/wp-content/uploads/pdfs/Total-Harmonic-Distortion-and-Effects-in-Electrical-Power-Systems.pdf

 

I really like the SuperCharger for the super clear RF like bitd with no faint vertical bars or graininess. Wish it could handle the 8K games.

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So it is possible that playing our new homebrews or a harmony cart can slowly be killing our 2600's? I'm just asking a general question, not necessarily related to my issue.

Edited by AtariLeaf

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It's not as if newer games overclock the 6507. Homebrews have been around for quite a number of years now, and I haven't heard anyone report that their CPU fried due to too much game awesomeness.

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It's not as if newer games overclock the 6507. Homebrews have been around for quite a number of years now, and I haven't heard anyone report that their CPU fried due to too much game awesomeness.

Thanks. I kinda realized it was a silly question but I thought I'd ask anyway

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So it is possible that playing our new homebrews or a harmony cart can slowly be killing our 2600's? I'm just asking a general question, not necessarily related to my issue.

 

It's not as if newer games overclock the 6507. Homebrews have been around for quite a number of years now, and I haven't heard anyone report that their CPU fried due to too much game awesomeness.

 

Good questions and good points.

 

In the course of my parallel research project on Motion Blur Reduction I destroyed two perfectly good classic CRT Televisions - STARBLITZ Party Games beta edition was responsible, it used many different video signals, the ones that broke the sets will stay unpublished settings to avoid damaging anyone's classic set.

 

Here's the research thread on the project for anyone interested:

 

https://forums.blurbusters.com/viewtopic.php?f=7&t=4135

 

Newer games don't overclock the 6507, but if they heavily load the ARM during the vertical blanks instead of the 6507 they create a pulsed interference pattern from creating a relatively stronger magnetic field and then collapsing it, see the links I provided earlier for an explanation.

 

I don't think it's going to degrade anyone's Atari anytime soon, I'd just like a clear display like bitd which is why I prefer to use the SuperCharger for compatible games.

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Harmony cart is unshielded?

 

Yes. I think you'd be hard pressed to find any third-party cartridges for the 2600 that actually use shielding in any way. Atari abandoned shielding for 7800 games, and there are some first-party Atari 2600 chip packages that were never shielded as well.

 

..Al

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And that was fine because there were no high frequency electronics in the cartridges. Insert a modern CPU or a Tesla coil into the cart and you need a Farday cage to keep the noise isolated (that's why old-school televisions have Faraday cages, a ground filter or isolated inverter won't help here).

 

AtariLeaf illustrated interference that can't be eliminated by a composite mod; why not modify a few harmony carts with really tiny Faraday cages to resolve?

 

I would buy one.

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As a cheap experiment why not line the insides of a noisy cart with foil, and ground that foil. See if anything changes.

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As a cheap experiment why not line the insides of a noisy cart with foil, and ground that foil. See if anything changes.

 

If you do this, please be very careful not to to short anything out on the board!!

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They make insulating tape to use for the electronics cavity of electric guitars... It would probably be cheap and perfect to try this. You could just apply it to the inside of the cart shell.

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They make insulating tape to use for the electronics cavity of electric guitars... It would probably be cheap and perfect to try this. You could just apply it to the inside of the cart shell.

 

The foil I use on my 5200 controllers from time to time would be perfect for this I think. I would still want to get some large heatshrink to put around the bulk of the guts of the pcb to make sure that over time the foil didn't start to peel from off the inside of the cart.

 

But yeah..some foil tape cut to size on the insides of the cart should work to at least test this out? I've never noticed any of this because I don't recall ever seen any interference with homebrews or my harmony that wasn't due to me using an RF cable at the time.

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