Is it fairly typical to find shielding in old Atari computers rusty?

[_The Doctor__]

yep and it is *part* of what we said so glad you dissected it all and put the metalguy stamp on most of it as it use to all be *bullsh!t* but now we see only the tiniest part in your eyes was actually ahem *bullsh!t* cause now it is all what you said in the first place!

 

Hey if your willing to act like an idiot, Im perfectly willing to ridicule you..

 

I said that the shield could (and does) influence the characteristics of the video output circuits..

 

I also said that there is no way in hell the shield is having an effect on the operational state of any of the digital circuits in the computer. This is easy to see from the stanpoint of common sense, if not actual expertise, as Poobah so kindly pointed out..

 

I also said that the machine does emit a field of it's own which does cause some degree of interference with RF/EMI sensitive devices close by..

 

You were the one insisting that without the shield, your atari would have major operational problems due to RF interference.

 

This is not the case, unless you attempt to operate your atari inside the transformer enclosure at a power substation, in close proximity to a high-powered welding device, directly under the emitter of an X-ray machine, during/after a nuclear attack, or in some other situation where the levels of emi are thosands of times higher than what you would normally experience in a typical home or office operating environment..

 

Like Poobah pointed out.. They dont use ANY SHIELDING nowadayze, on devices that operate at hundreds of times faster bus speeds, with 3.3v or 1.2v voltage levels.. These devices are literally HUNDREDS of times more susceptible to inductive interference.. So much so, in fact, that they have entire books and engineering courses dedicated to these issues.. So why dont they put shielding on these devices like they did on computers in the 80s? The answer is.. (surprise, surprise) That at lower operating voltages, and higher frequencies, the devices actually EMIT LESS interference and arent likely to screw up the operation of anything around them.. Also, as Poobah pointed out, the FCC regulations were a bit rediculous in the 70s & 80s..

 

 

I looked and looked for major operational issues in my post and could not find it. I did say it affected the speed and operations of I/O devices as did marius. I did say I experienced some lock ups.. and that is true... I did say putting the shield back on solved the problems. that is the truth. And the atom splitting problem is what?

Is it not a possibility since the Atari uses signals and tones to send cassette information and sio information that other tones and noises present on the sio bus could interfere or be mis-interpreted? Could that lead to error or a crash or lock up? You are looking at just one aspect.

 

My Atari operates at the same low frequency as it did way back when. With the same circuits laid out not taking any positioning of components into account. The devices connected to it use 12v and 5v systems not 1.2v systems. My Falcon required toroidal coils to take interference of the lines when I put a speeder in it. The clock pulse digital the computer digital and yet the designer put that in because it was required to keep the noise off the bus. Without the simple toroid beads... errors. with it perfection. Do you think maybe the noise was amplified to a degree that caused a problem?

 

I like how we mix it all together with enough stuff added and wrapped into it it all sounds the same but are different cases entirely. Higher freq. is less susceptible to interference no kidding why old cordless phone use to s*ck and messed up horribly. In theory they were suppose to work the same as anything else without interference. we found out differently and look ma they made em 800 them 900 MHz and then took em to the gigahertz.

 

The way circuit boards are shielded and sandwiched today as well as the way they are laid out effects all of the issues, today we know how to position components so they no longer interfere with surrounding items the direction a component faces and how it lies are taken into account the insulating material are better. This goes right down to the circuit boards certain noisy sections are no longer placed anywhere near items that could be effected such as audio or video circuits. An extreme amount of care is put into the design so that it is protected. Less power and voltage makes for lesser weaker signals and faster switching... common sense.If noise and RF are not factors then clip all the filter capacitors off the all the pcbs cause it is not an issue, right? The kitchen sink also in effort to effect even more change they are lowering television output power and making the broadcast digital, in theory making me receive crystal clear perfect tv where I live. I reality I lost 20 channels that use to be perfectly fine but the digital signal is far more influenced by error and other digital interference and harmonics but hey it's digital so it should in theory be perfect!

This is all academic.

[Marius]

Since I'm 'quoted' several times here, I say it again:

 

In my situation i'm 100% positive it is not the RF-disturbance thing, but the fact that the shield adds some extra mass to the computer.

 

When I remove the shield, but add extra mass to the computer, or to the myide interface it works perfect.

 

Even changing powersupply (A PC PSU) which has a larger case, the problem is gone.

 

I don't know if this 'mass' thing might work in a positive way with other problems, but that might be a good reason for not removing it.

 

@Doctor: like me you have same experiences with and without shield. But don't forget: you MIGHT have the wrong conclusion about the reason why your shield has a positive effect. It can be everything. Even this is possible: perhaps is your motherboard crippled and with the shield it is fixed in a certain position, which might be the reason it works better. Probably not the reason, but I try to illustrate that -like in my situation- there are different conclusions possible. In my case i'm positive it is NOT a RF issue.

 

And about the high frequency issue. The strangest is, that even with the shield installed, the atari still produces and sends out a lot of RF garbage. I'm a licensed radio operator, and I've had lots of issues with RF disturbance due to the Atari, but even with shield installed, some frequencies on the radio got a 9+DB signal from the atari :S

[_The Doctor__]

yep she is very leaky. I don't think they understand what you mean by mass. I do know adding length of wire can change the wavelengths involved. Does it make a difference if you add mass to the +5 volt as opposed to the ground side. I remember when we had to add toroidal coils, beads and balls to the tandy color computers to soak up the interference those beasts put out as well as keeping stuff from going in.

 

You have a call sign?

73's

_The Doctor__

Edited February 4, 2009 by _The Doctor__

[Marius]

With mass I mean grounding-mass. I'm not so good writing english. That is a problem sometimes.

 

My call sign is a dutch one:

 

PD5MDB

 

Greetz

M.

 

p.s. with this license I can operate on 2meter and 70cm frequencies.

[_The Doctor__]

Here in the States the Atari is not earth grounded in the conventional sense. It is isolated from ground by its transformer based power supplies. The actual grounding occurs only when attached to a properly grounded Televison or monitor. The chasis can act like it's own ground plane in some situations.

[_The Doctor__]

You Know You're a Ham if :

 

- you buy electrical black tape in ten packs.

- you've stripped wire with your teeth.

- you've told your son that, "One day, all this will be yours", and he doesn't respond.

- you'd rather help a buddy put up a new tower than mow the lawn.

- you've grabbed the wrong end of a soldering iron.

- you start giving out RST reports when you are on the telephone.

- the propagation forecast means far more to you than the local weather forecast.

- the microphone or visual aids at a meeting don't work and you rush up to the front to fix it.

- you tell the XYL, when she notices a new rig in the shack, why that has been there for years.

- your watch is set only to UTC.

- at night, when you pray, it starts off something like: CQ CQ CQ GOD DE (your callsign).

- you ever had to patch your roof after an antenna project.

- Ham radio magazines comprise more than 50% of your bathroom library.

- you ever put a GPS tracker in the XYL's car, just so you could watch her on APRS.

- you and the XYL took a cruise so you could visit the radio room.

- you ever tapped out HI in Morse on your car horn to another ham.

- you ever had an antenna fall down.

- your teenager refuses to ride in your car because it looks like a porcupine.

- you know the Latitude and Longitude of your home QTH.

- in america, you go into the local Radio Shack store and the clerk asks you where something is.

 

I laughed when I first heard these!

Edited February 4, 2009 by _The Doctor__

[MEtalGuy66]

Is it not a possibility since the Atari uses signals and tones to send cassette information and sio information that other tones and noises present on the sio bus could interfere or be mis-interpreted? Could that lead to error or a crash or lock up?

Sure.. And you get plenty of that with or without the shield on the motherboard..

 

My Atari operates at the same low frequency as it did way back when. With the same circuits laid out not taking any positioning of components into account. The devices connected to it use 12v and 5v systems not 1.2v systems. My Falcon required toroidal coils to take interference of the lines when I put a speeder in it. The clock pulse digital the computer digital and yet the designer put that in because it was required to keep the noise off the bus. Without the simple toroid beads... errors. with it perfection. Do you think maybe the noise was amplified to a degree that caused a problem?

 

And this relates to the shield how?

 

I like how we mix it all together with enough stuff added and wrapped into it it all sounds the same but are different cases entirely.

Hey you are the one throwing in all this irrelevant crap.. hahah.. Im just repeating the same thing and hoping you'll get it..

Higher freq. is less susceptible to interference no kidding why old cordless phone use to s*ck and messed up horribly. In theory they were suppose to work the same as anything else without interference. we found out differently and look ma they made em 800 them 900 MHz and then took em to the gigahertz.

No shit, Sherlock.. Who's "mixing it all together with enough stuff added and wrapped into it"? Everything anyone else has contributed to this conversation has been alot more relevant than the crap you are talking about now..

The way circuit boards are shielded and sandwiched today as well as the way they are laid out effects all of the issues, today we know how to position components so they no longer interfere with surrounding items the direction a component faces and how it lies are taken into account the insulating material are better. This goes right down to the circuit boards certain noisy sections are no longer placed anywhere near items that could be effected such as audio or video circuits. An extreme amount of care is put into the design so that it is protected. Less power and voltage makes for lesser weaker signals and faster switching... common sense.If noise and RF are not factors then clip all the filter capacitors off the all the pcbs cause it is not an issue, right?

Whose point are you making here? The reason they do all that crap is because due to the low voltage & fast switching times, circuits are more succeptable to interference than ever.. The fact is, you dont see them shielding the entire PCB in metal to keep interference from external sources out.. Thats the point.

The kitchen sink also in effort to effect even more change they are lowering television output power and making the broadcast digital, in theory making me receive crystal clear perfect tv where I live. I reality I lost 20 channels that use to be perfectly fine but the digital signal is far more influenced by error and other digital interference and harmonics but hey it's digital so it should in theory be perfect!

Man.. Im sure glad you arent "mixing it all together with enough stuff added and wrapped into it." I don't know how you manage to come up with such pertainant and relevant information.

This is all academic.

That's for damn sure..

[UNIXcoffee928]

Wasn't this about rust?

 

The shielding has rust because your old pet, "Rusty" pissed into it 25 years ago, shortly after after you had spilled the Pepsi all over it when playing "River Raid", then your younger brother washed it all off by swishing it around in the fish tank for you. ("Oh, yeah, it's all coming back to me now, that's right!")...

 

= )

 

 

Aside from RFI, and more importantly, in the short term, try to avoid Lockjaw... RF shielding can have some sharp edges...

 

= )

 

 

In other news, functional RF shielding requirements tend to change slightly if you, or your friends, have a B.F.A. on top of your houses....

 

= )

 

 

...however, I don't want to stand in the way of a juicy analog/digital drama...

 

 

in fact, maybe someone can offer some useful advice as to how/where I can add additional shielding/RF isolation to my Marshall tube amp head... it seems that when it is fully overdriven that it likes to pick up a local religious station's broadcast...

 

...fairly low, but still audible, and though comical sometimes, it is annoying... only can be heard when I'm not playing, while the amp is still on & ready to go. Usually only noticeable when it is all the way L O U D (@11).

 

Something is acting as an antenna, apparently, whether it's in the head alone, the effects loop, or the guitar to amp input area, I haven't determined yet, but I swap cables often, so it is unlikely to be cables. Some advanced RF troubleshooting tips would be greatly appreciated.

 

 

Thanks!

[yorgle]

Wasn't this about rust?

 

 

in fact, maybe someone can offer some useful advice as to how/where I can add additional shielding/RF isolation to my Marshall tube amp head... it seems that when it is fully overdriven that it likes to pick up a local religious station's broadcast...

 

...fairly low, but still audible, and though comical sometimes, it is annoying... only can be heard when I'm not playing, while the amp is still on & ready to go. Usually only noticeable when it is all the way L O U D (@11).

 

Something is acting as an antenna, apparently, whether it's in the head alone, the effects loop, or the guitar to amp input area, I haven't determined yet, but I swap cables often, so it is unlikely to be cables. Some advanced RF troubleshooting tips would be greatly appreciated.

 

 

Thanks!

 

Are you sure it's a religious radio station and not God himself trying to talk to you through your amp?

[UNIXcoffee928]

Are you sure it's a religious radio station and not God himself trying to talk to you through your amp?

Bob played Black Sabbath >BACKWARDS< at 78 Speed, and he SAW God!!!

[MEtalGuy66]

Now heres an application where good shielding can definitely make a difference.. Make sure the entire input side of your rig uses quality shielded cables & good connectors.. Also, make sure any cheap "stomp boxes" youve got in-line with the input are either metal, or shielded internally.. Also, theres the guitar.. The "electronics cavity" inside most higher quality guitars has some form of shielding. Maybe a layer of metal foil, or sometimes just conductive paint.. If it's a cheap guitar, you could possibly get some improvement/noise reduction by increasing the shielding there..

 

But after all that is all said and done.. Heh. Im afraid its the "nature of the beast" on an electric guitar.. The thing WORKS by amplifying harmonics which exist in the reluctance of the field generated by the pickups(due to the vibration of the strings, of course).. The pickups are basically sensitive "recievers" by design... If all your gear is shielded good, the amp & other equipment has a good ground, and you still pick up radio stations when you crank up the gain, you'd probably have to SHIELD THE ROOM to get rid of it..

 

If you wanna try and "track down" the problem, I'd start with the obvious "process of elimination"... Does the problem still occur with the effects loop bypassed/removed? Does the problem still occur with the guitar plugged directly into the amp input via a very short (and good quality) cable?

 

Also, what model head is it? My friend's JCM800 had some issues internally that made it really noisy.. He tried all kinds of crap to fix it, and finally ended up taking it to a guitar shop.. I dont know what they finally did to fix it..

Edited February 4, 2009 by MEtalGuy66

[UNIXcoffee928]

It's a Limited Edition (red version, w/spring reverb) Marshall Artist 3203 head & matching 8x10" full stack. All of my guitars are professional quality. I tend to use my Fender Jazzmaster with it most, as it's my fav.

 

Yeah, I pretty much answered my own initial question, with regard to step by step elimination-type troubleshooting... I always put it off, because it's no fun troubleshooting things with your head close to a loud amp... will get to it, though. In fact, just stating this, I'll also try each guitar through it during the process of elimination, to get a better idea.

 

It has had a lower priority lately, since my GK 800RB bass head died mysteriously, much to my anguish & dismay... still trying to get that back in shape. Constantly fixing things... arrrg!

 

Room... yeah, it's a mad scientist's laboratory/electrician's nightmare/rat's-nest of cabling, floor to ceiling... ha... but it is Organized Chaos, & I do try to keep different types of equipment on separate circuits.

 

I have seen large CRT monitors, florescent lighting, and electric heaters cause adverse effects on other people's (otherwise good sounding) amps (both tube & transistor) in other locations (even in music stores!).

 

So anyway, yeah, I will be doing the step by step elimination troubleshooting, but what I was interested in were other ideas, regarding adding additional metal shielding inside/outside of the amp head, and maybe some info on the way that magnetic rings work on cables, proper use, etc.

 

Just general RF systems-oriented advice needed, pretty much. I mean, having God speak to me when I play is fine enough at home, but might be a bad idea on stage (Spinal Tap stylee)... ha... meaning, the operating environment for this device changes, so, are there any "best practices" mod ideas that I can apply to ensure that other RF interference doesn't cause a problem at random club location X, Y, or Z in a situation where the cabinet will be mic-ed and running through a club's PA (thus being even louder)?

 

This is an issue, because I can't accurately simulate all potential environmental conditions.

 

Right now, the "Stand-by" switch effectively shuts off the broadcast, between songs, but I should, ideally, have a more elegant solution at my disposal.

 

...& I don't want to lead the whole thread crazily off topic, so info on multi-location, generalized systems-oriented RF interference protection would probably be best, to benefit everyone.

 

 

Thanks!

[+bf2k+]

in fact, maybe someone can offer some useful advice as to how/where I can add additional shielding/RF isolation to my Marshall tube amp head... it seems that when it is fully overdriven that it likes to pick up a local religious station's broadcast...

 

I had an old Marshall that did exactly the same thing!!!! I fixed it tho... Sold it and got a Mesa Boogie!!

[+poobah]

So i've been rolling the shielding thing around in my head today....

If you have internal crosstalk, the shielding could make it worse...

 

Stay with me of this one.

 

The idea of the shield is to prevent signals from getting into or out of the shielded section, and therein lies the rub.

If you have a noisy item on the motherboard and no shielding, the noise will radiate out into the environment,

 

However with shielding in place things change....

 

You would hope some noise would get coupled to ground, but the shielding is not a perfect antenna, and metal is a wonderful scatterer, so a certain amount of stray noise will be reflected back to motherboard that wouldn't be there if it was allowed to radiate out into the environment. (which incidentally, is why the radio section of modern wireless routers is inside a metal box, so it doesn't interfere with the other internal circuits.)

 

As for the talk of chokes and what not in the falcon.... that's to deal with internally generated noise, not noise from 'the local ham' and has nothing to do with removing the shielding in the XL.

 

On the amp... you may want to check the inputs and also make sure that shield grounds terminate at a single point and that they are only grounded at the end nearest that point (otherwise you made an antenna and a capacitor)

Edited February 4, 2009 by poobah