Is the RF shield necessary?

[jacknutting]

A couple of months ago I installed an A/V output mod on a 2600. The set of instructions I was following told me to remove the RF shield and just throw it away. I did so, and it seems to be fine.

 

So now I'm looking to start modding a 7800. Once I get the RF shield loose, can I just throw it away, or does it serve any real function that requires it to be there?

 

My (limited) understanding is that these things are there to satisfy regulations about RF signals being emitted from a device, and that the only downside of leaving the shield off is the slight risk that I might pick up some "noise" on other nearby devices when using the 7800 later. I'd love to have this idea either confirmed or refuted by someone who really knows!

[Keatah]

..or the 7800 could pick up noise. Or transmit it to your nearby display device or its cables. If something comes with a shield, it's best to use it. It's there for a reason. And the FCC as well anyone with a degree in telecom hardware would tend to agree. Keep in mind interference is tricky little beast and there are many factors involved in what makes it rear it's ugly head and when.

 

Whatever directions are telling you to throw parts away are, like, so idiotic. You shouldn't throw anything away, especially classic videogame parts. Just as bad as that one set of instructions telling the installer to cut out the RF modulator and throw IT away too! You don't go cutting parts out willy-nilly. You desolder them with appropriate tools and set 'em aside or affix them to the inside of the unit for the future - for whatever reason.

[jacknutting]

Thanks! This is an interesting counterpoint. I threw away both the RF shield and the RF modulator itself when I modded my 2600. I guess I was following the same set of instructions you're thinking of. I definitely see your point about not throwing away classic videogame parts, but in that case it is a VERY common 2600 model so I don't feel too bad about it But I want to be more careful with the 7800. I will strive to keep it in good shape, and will reattach the shield!

[+sixersfan105]

I agree you should refrain from throwing out retro gaming system parts, but back to the original question, nothing bad should happen in 2017. Yes, the shield is there to keep RF signals from bleeding both in and out. That said, in the 70s and 80s, RF signals were everywhere. Today, there are very few (if any) modern electronics that utilize RF. Something to keep in mind.

[DrSidneyZweibel]

..or the 7800 could pick up noise. Or transmit it to your nearby display device or its cables. If something comes with a shield, it's best to use it. It's there for a reason. And the FCC as well anyone with a degree in telecom hardware would tend to agree. Keep in mind interference is tricky little beast and there are many factors involved in what makes it rear it's ugly head and when.

 

Whatever directions are telling you to throw parts away are, like, so idiotic. You shouldn't throw anything away, especially classic videogame parts. Just as bad as that one set of instructions telling the installer to cut out the RF modulator and throw IT away too! You don't go cutting parts out willy-nilly. You desolder them with appropriate tools and set 'em aside or affix them to the inside of the unit for the future - for whatever reason.

This is completely wrong.

 

The RF shield was only ever required for the 7800's potential to disrupt analog OTA RF video signals in OTHER devices, not the 7800 itself. Analog RF OTA signals have been replaced outright by digital OTA signals for a few years now.

 

You do not need to keep the RF shielding if you're only using an AV mod.

Edited December 13, 2017 by DrSidneyZweibel

[+save2600]

...Analog RF OTA signals have been replaced outright by digital OTA signals for a few years now.

 

There still exists *some* analog OTA TV stations. We get this quirky but fun channel out by us, albeit with some snow:

 

http://www.wrpq.com/tv-channel-43/

 

https://en.wikipedia.org/wiki/W43BR

[Keatah]

This is completely wrong.

 

The RF shield was only ever required for the 7800's potential to disrupt analog OTA RF video signals in OTHER devices, not the 7800 itself. Analog RF OTA signals have been replaced outright by digital OTA signals for a few years now.

 

You do not need to keep the RF shielding if you're only using an AV mod.

 

..and have the harmonics of the logic circuits interfere with other devices. Or accept same style interference. You are in error.

[fiddlepaddle]

You know, it's pretty galling to see someone say nobody is using 40 year old RF devices anymore when specifically talking about using a 40 year old RF device...

[DrSidneyZweibel]

You know, it's pretty galling to see someone say nobody is using 40 year old RF devices anymore when specifically talking about using a 40 year old RF device...

if youre using the rf output of the device you may want to keep the shielding in place.

 

If youve modded the system with composite/svideo/rgb and removed the rf, theres no need for the shielding. It will have no effect positive or negative on the video out out of your 7800 or the video input of your television.

 

And nobody here said nobody is using rf so theres no reason to be galled. The question was do you really need to keep the shielding. If youre not using the rf, you dont.

 

Furthermore, this is only an FCC requirement, based on an extremely dated and vastly overcompensating standard that no 8-bit, 16-bit, or later video game consoles ever exceeded. No other country required such standards, consoles in Japan and other countries dont have the same shielding and there is no ill effect on the video signal or any other rf devices.

 

Purists can do what they feel is necessary to satisfy there own personal rigid standards of OCD purism.

[+-^CrossBow^-]

I personally try and leave the shielding in place whenever I can. However, as was stated with an AV mod in place, the shielding isn't nearly as big a deal. Even still, I keep it for one pretty important reason...

 

The 7800 main board expects those two sections of aluminium to be on the bottom and top. As such, the entire mainboard doesn't fit snug without the shielding in place I've noticed. Same with the Sega Genesis. However, the JPN Mega Drives do not have any shielding at all. But that is also because the JPN Mega Drives do not have RF output to begin with.

[+wongojack]

So, I bought a modded 7800 a few years ago, and I just opened it up. The screw holes were cracked and in bad shape and the case itself was cracked in a couple places.

 

Anyway, if I try to power it on without the RF shield in place, it will not power up. Put the shield back in place and it comes back. I thought I might probe around and try to figure out if the shield is connecting a ground or something, but I wanted to ask and see if someone else has hit this same problem. If so, did you attempt a fix or just leave the shield in place? If you can help me shortcut this troubleshooting, I would appreciate it.

[+-^CrossBow^-]

7800 mainboards should power up and operate without any shielding. I test the 7800s I've modded on my esd mat with the main board just sitting there no shielding at all and they power up just fine. Now what I have had happen, is that the shielding was touching points along the power switch it should not have been and was causing the 7800 to either not power up, or power on randomly.

 

But no, that isn't normal and the 7800 should power up normally without the shield in place at all. If it isn't, and only seems to when the shielding is on, then there is a ground missing that the shielding is completing. I would start with the power switch first and move along the ground plane for components that touch it to see if something has a cold solder joint that makes contact when using the shielding.

[+wongojack]

7800 mainboards should power up and operate without any shielding. I test the 7800s I've modded on my esd mat with the main board just sitting there no shielding at all and they power up just fine. Now what I have had happen, is that the shielding was touching points along the power switch it should not have been and was causing the 7800 to either not power up, or power on randomly.

 

But no, that isn't normal and the 7800 should power up normally without the shield in place at all. If it isn't, and only seems to when the shielding is on, then there is a ground missing that the shielding is completing. I would start with the power switch first and move along the ground plane for components that touch it to see if something has a cold solder joint that makes contact when using the shielding.

 

Yeah, that was where I was going to start. Or, I might just jam the shielding on there and hope for the best - lol

 

If you happen to get a 7800 open and can photograph what you are talking about where the shielding touches points "along the power switch it should not have been" that could be helpful to me and even others who come along after me.

[masschamber]

the rf shielding is the to prevent sending and receiving interference, without it rf will have more interference. Av mod and it won't really matter.

[+-^CrossBow^-]

Easy..the power switch is located in the lower left and the shielding can easily touch the points on the top edge of the power switch where the solder points are located. The other issue, and this is rare but I've seen it happen. Atari wasn't the greatest about clipping the leads very well on many of the components and I've seen those short out on the bottom RF shield sometimes. So when I mod a console for someone, I will go over the bottom of the board and trim up any leads that didn't get trimmed at the factory properly or were just folded over.

[John Stamos Mullet]

the rf shielding is the to prevent sending and receiving interference, without it rf will have more interference. Av mod and it won't really matter.

If your 7800 is av modded, it's not using RF. the whole point of av modding these is to remove RF interference.

Edited August 22, 2018 by John Stamos Mullet

[masschamber]

If your 7800 is av modded, it's not using RF. the whole point of av modding these is to remove RF interference.

exactly

[+-^CrossBow^-]

Believe or not RF is actually still quite prevalent all around us. All wireless communications including Bluetooth uses RF. RF meaning Radio Frequency. So if anything there is more RF around us than ever imagined 20 or 30 years ago. And don't forget the whole reason that analog TV was finally put to pasture was because the FCC required more for use in our current cell phone infrastructure.

 

The point is, that RF is still very much all around us and actually more of it. Besides...I've still done AV mods on consoles that during testing would still show interference in the video signal even on composite until I put the RF shielding back on. So yes, AV modding a console helps considerably with this, but you can still have interference that affects the ICs in the system that create the initial video signal and still have that show up. Like the jail bars on the Sega Genesis in composite and s-video which is interference from the color sub-carrier and dirty power rail that runs near the RGB lines from the VDP to the encoder.

 

Or the jail bars many report with the 5200 AV mods also on composite and s-video? So in my opinion...if you can find a way to put that RF shielding back on...do so.

[Andromeda Stardust]

I trashed the lower shield of my NES while trying to carve a hole in it with a dremel tool to install the CopyUSB NES addon. Years later, I trashed the upper shield after installing the blinking light win. Your mileage may vary, but generally there is no harm in removing shielding. You'd be surprised at how many modern devices have no internal shielding at all.

 

Rule of thumb, if the shield gets in the way of a mod install, toss it. But if it isn't getting in the way, you may as well leave it in place. Worst case scenario, you get interference after tossing the shield and you can no longer replace it.

 

Also some game consoles use the shielding as a heat sink extension for CPUs or regulators. Best to leave them in place if any component with the potential to get warm is bolted onto it.

[Jinks]

I trashed the lower shield of my NES while trying to carve a hole in it with a dremel tool to install the CopyUSB NES addon. Years later, I trashed the upper shield after installing the blinking light win. Your mileage may vary, but generally there is no harm in removing shielding. You'd be surprised at how many modern devices have no internal shielding at all.

 

Rule of thumb, if the shield gets in the way of a mod install, toss it. But if it isn't getting in the way, you may as well leave it in place. Worst case scenario, you get interference after tossing the shield and you can no longer replace it.

 

Also some game consoles use the shielding as a heat sink extension for CPUs or regulators. Best to leave them in place if any component with the potential to get warm is bolted onto it.

Your a one man wrecking crew with that dremel!

[nick3092]

Believe or not RF is actually still quite prevalent all around us. All wireless communications including Bluetooth uses RF. RF meaning Radio Frequency. So if anything there is more RF around us than ever imagined 20 or 30 years ago. And don't forget the whole reason that analog TV was finally put to pasture was because the FCC required more for use in our current cell phone infrastructure.

 

The point is, that RF is still very much all around us and actually more of it.

To this point, I would say either modern parts or modern designs have probably increased resistance to RF, as it's still very much around. Even looking back at vacuum tubes, they used to require external shields around the outside of the tubes to avoid picking up hum or causing the tube to go into oscillation. But later on In the twilight years of tubes, they figured out how to build shields inside the tubes, so you didnt have to put on external metal shields. No reason to believe they haven't done something similar with solid state parts now days.

[+-^CrossBow^-]

To this point, I would say either modern parts or modern designs have probably increased resistance to RF, as it's still very much around. Even looking back at vacuum tubes, they used to require external shields around the outside of the tubes to avoid picking up hum or causing the tube to go into oscillation. But later on In the twilight years of tubes, they figured out how to build shields inside the tubes, so you didnt have to put on external metal shields. No reason to believe they haven't done something similar with solid state parts now days.

Oh and I'm sure that is true..but we are talking about 30 - 40 year old electronics here and those components aren't designed to be internally shielded.

[+wongojack]

The problem on my 7800 is that the heatsink behind the cart slot is loose. With the top shield off, I figured out it would power up if I held the heatsink in a specific position. It was just a coincidence that the RF shield sorta held it in place. I think that the voltage regulator attached to the sink must be coming loose. I'll have to pull the board completely out of the case and check the contacts (probably reflow them). I think the modder must have made it loose twisting the fasteners that hold the RF shield in place - strike 1 modder.

 

That kinda sucks because the AV mod on this is the old Longhorn Engineer one and involves a bunch of small wires that could come loose. The modder also hot-glued the jacks in and I might have to pull them out - strike 2.

 

The reason I was opening the unit in the first place is that the 2600 colors were completely off. I had to adjust the pot to get them right - strike 3.

 

 

Good thing I bought this years ago for a really good price . . .

[Keatah]

Some modern parts have shielding built in. 'pends on the app. And some parts have special shapes of wires and layouts inside them to further their RFI resistance.

 

If a vintage console had/has shielding then it it should be maintained and repaired as if it were part of the circuit. It was put there for a reason. Don't be a tough macho-man and discard shielding willy-nilly. If you have to mod something, and the shield gets in the way, figure out a way to work around it and with it. That's smart.

 

If a console has a shield that's causing heat issues. Stick a tiny fan in there to circulate air, or thermally couple the part to the shield for added cooling.

 

An added benefit of shielding is to protect not only against RFI but static electricity buildup too. And 40-year old electronics can get all the help available in that department if we want another 40 years out of them.

 

Furthermore it is possible to generate RFI (from outside the console by another device) in just the wrong way to cause the console to lock hard in a state it would never ever do on its own. And this sort of temporary failure can shorten the life of the console, or kill it on the spot.

 

I inadvertently did this with my cellphone, bringing it close to a SouthBridge.. And bam, instant lockup on dial-out. Not long after, the USB ports failed and the SB started running hot and the system would slow down complaining of disk errors.

Edited August 23, 2018 by Keatah

[Keatah]

Oh and I'm sure that is true..but we are talking about 30 - 40 year old electronics here and those components aren't designed to be internally shielded.

 

Quite right, they're designed to be externally shielded. Hence the prevalence of shielding in classic rigs.