>>
>>
>> I really have been trying to follow this conversation but my head
>> is swimming. Could someone please sum up what they consider the
>> best course of action is in grounding a vector game in layman's
>> terms. ....I knew I should have stuck to my EE major.
>>
> Well, it is not quite that simple. Certainly when one is designing a
> product and wishes to use the best possible design to eliminate ground
> loops, electrical noise, and other oddities - one designs using the
> single Star (Common) system.
>
> Unfortunately in the real world the star system breaks down at the
> junctions and then you get problems with different ground potentials
> building up between various sub-components in the system.
>
> Now, if you are passing signals to each component via an isolated path
> (optical isolators for example) then these ground variations do not
> matter. However when dealing with Vector monitors - primarily the
> Sega/GO-8 system - when the grounds start to fail (not if - when) then
> the ground reference for the X & Y signals drifts with the ground
> fault. This can lead to ground/common voltage differences between
> sub-assemblies which can be enough to bugger up the bias of the XY
> deflection circuit so the output transistors are pushed into illegal
> drive states (my supposition), leading to failure.
>
> So, I (and others) recommend that a SECOND ground/common star is
> installed to add redundancy to the system and help prevent this
> problem from occurring.
>
> This second ground/common IS redundant in a well maintained game
> (polished power connectors that run cold to the touch), but in many
> games this is simply not the case and the second ground system will
> protect (if installed correctly) as the primary ground/common was
> designed to do - but fails due to connection issues developing over time.
>
> Please note, I am NOT an electrical engineer, rather a self-taught
> technician who found this solution back in the mid-1980s (originally
> figured out for Gottlieb Pinball Games that were blowing coils at
> random) and I have since found that this solution works in most power
> systems that use a common ground and where these ground/common
> junctions are not bolted together.
>
> John :-#)#
Ok, I'm glad John clarified because this is an important point. John is
talking about adding another (and better) ground as both a failsafe and
also to get better current flow where lousy connections exist.
What I'm discussing is somewhat the opposite: *removing* any redundancy
(which can lead to ground loops and potential problems from having
them), and essentially re-engineering the original lousy connections,
wiring, and main grounds to establish an improved ground scheme.
Our goals are the same, but the methods differ. John's suggestions
are far better than having lousy grounds, no doubt. My suggestions are
harder to pull off, and have to be very well-made (and perhaps even
occasionally maintained) because you're relying on single point
connections.. there is no redundacy.
Note that John's ideas sprung from the electromechnical world where
ground loops aren't as problematic as in the audio, video, and digital
worlds.
JS
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Received on Mon Sep 15 11:58:21 2008
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