Is the RF shield necessary?

[John Stamos Mullet]

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.

The shielding is there for the singular purpose of preventing RF interference. Both coming and going. If you remove and disable the RF components, and use an AV mod, there is no longer a need to shield anything, since the RF unit is no longer functioning - and therefor no longer causes, nor receives RF interference.

[+-^CrossBow^-]

The shielding is there for the singular purpose of preventing RF interference. Both coming and going. If you remove and disable the RF components, and use an AV mod, there is no longer a need to shield anything, since the RF unit is no longer functioning - and therefor no longer causes, nor receives RF interference.

The RF modulator isn't the only component effected by RF...that is what we just stated.

 

And I've seen it for myself. Even with the UAV mods if I move the wiring around etc, I can see interference patterns appear. Heck I installed 75ohm terminators in the unused BNC connections on the back of my Extron video selector to help minimize the inference I was still getting from the BNC connectors acting like antenna when not in use. There is not RF required for the extron, but yet the internal components still receive some interference from RF signals stray in the air and it was built in 2003 and costs several $$$$ when new.

 

Just because you aren't using the RF modulator doesn't mean that RF still isn't an issue in these older electronics.

[Keatah]

The shielding is there for the singular purpose of preventing RF interference. Both coming and going. If you remove and disable the RF components, and use an AV mod, there is no longer a need to shield anything, since the RF unit is no longer functioning - and therefor no longer causes, nor receives RF interference.

 

Most vintage consoles have a small box on the mainboard, the RF modulator, that's inherently shielded already, it's a small metal and enclosed box. Shielding its parts 2x does little to improve things beyond 1x.

 

The other components are why shielding is needed. Maybe not for the exact direct operational frequency, but also for their harmonics. Think beating frequencies and rattling walls. Resonating headaches.

 

The C64, IIRC, even has small metal dividers/boxes for select parts. To prevent them from pissing off each other.

 

And with the cover off my Apple II drives an AM radio crazynuts. Heh! Even with the cover on it's only marginally better.

Edited August 23, 2018 by Keatah

[+-^CrossBow^-]

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 heat-sink on the 7800 isn't that well anchored to begin with and I've seem them come loose just from the ages of time and being moved around. They are a bear to get anchored back in but you can try and heat up some solder to attach to the heatsink to try and get it to stay, but it will Sink the heat so you will have to use a ton of heat to do this. Also if you apply enough solder to the voltage regulator, that should anchor the heat sink in enough for most use without being much of a problem.

 

As for hot glue...I try and NOT use it when I can, but depending on where the jacks were installed on the 7800 and what kind of jacks were used....hot glue can and is used to help anchor the jacks in place but it shouldn't be the ONLY thing holding them in place. I've now got some 1/4 inch open star washers that I use in addition to the other fasteners on the RCA jacks and have found that I can really get them in there tight using those on the backside of the jacks with the nut to secure them down. I still apply a bit of gorilla super glue around the jacks where they meet with the plastic housing to be sure though.

[CZroe]

I had one over a year ago that just wouldn’t run 7890 games with the RF/EMI shield in place unless you let it warm up for nearly 15 minutes:

https://youtu.be/XNOQk1nQaEQ

 

Conclusion: No more lower shield.

Edited September 18, 2018 by CZroe

[cedropoole]

On my recent Atari 7800 A/V composite mod I completely removed the RF module for better placement of the RCA jacks. I initially noticed that the video and sound were less than optimum. I then removed the top of the RF shield and left the bottom of the RF sheild in place and Voila!, miraculously both the sound and video are now optimum. What's the explaination for this? 

[CZroe]

On my recent Atari 7800 A/V composite mod I completely removed the RF module for better placement of the RCA jacks. I initially noticed that the video and sound were less than optimum. I then removed the top of the RF shield and left the bottom of the RF sheild in place and Voila!, miraculously both the sound and video are now optimum. What's the explaination for this? 

What are you using for a power supply?

I think you might want to see all the things Perifractic tried to solve a similar issue in this video:

[cedropoole]

The power supply is an OEM original. As for an explination, I'm just happy it's working so well. My experience with repairing 70's and 80's technology has shown many black magic repairs where I do so many combinations of 'Fixes' during a mod that when I finally get it at optimum proficiency I have no idea which fix or combination of fixes made it happen. I built his dual stick Genesis/Atari 7800 hybrid. I have a Seagull 78 adapter on the Genesis side for an awesome Robotron 2084 experience.