Re: SEGA to Amplifone converter

So as it pertains to this discussion, an Amplifone and a WG6100 will
perform the same? I'd filed a mental note that the Amplifone was
'faster' than the WG6100 which is why I asked the question. But as
they use the same voltage supply and similar yoke impedance, I'm now
thinking it's not speed but rather the better (medium) resolution that
makes me think of the Amplifone as superior. Does the tube's
deflection angle affect its speed?

Full disclosure: my grand scheme was to build a 25" Amplifone and see
it if would fit in a Star Trek sitdown. Then we're back to a 100
degree tube and the yoke from a WG6100....

-Douglas

On Jul 15, 2009, at 9:46 PM, Zonn wrote:

> Clay Cowgill wrote:
>>> I found David Shuman's info on building a converter to run SEGA
>>> vector games on Atari XY monitors, including a caveat that it
>>> can't seem to keep up when there are a lot of vectors to draw.
>>>
>>
>> That more or less mirrors my experience. It was fine for testing and
>> tinkering, but I probably wouldn't want to use it as a final
>> solution.
>>
>>
>>> David postulates that it's a bandwidth problem with the
>>> amplifiers. Could the cause be the slew rate of the WG6100? Since
>>> the Amplifone is faster, perhaps the converter would work 100%
>>> when using an Amplifone? Anyone have any experience running this
>>> setup?
>>>
>>
>> I really don't remember what I did when I used my Wg6100 on the
>> SegaMultigame prototyping. I probably had something very similar
>> to David's
>> circuit if it wasn't the actual one he posted. (The timing is quite
>> suspicious since that's about when I was working on the Sega
>> Multigame, so I
>> probably saw his post and tried it.)
>>
>> As I mentioned before in another thread, probably 98% of things
>> looked fine,
>> but that 2% resulted in visible tearing. I mostly noticed it when
>> there was
>> a large delta between points (not necessarily just when there was
>> "lots" to
>> draw). I'd wager a guess that that was the fallout from GO8 being
>> able to
>> reposition the beam faster than the WG6100 could. (In the Atari
>> AVG's you
>> generally don't ever jump the beam more than half a screen width at
>> a time,
>> so the SegaXY vector generator doing that probably exceeds the
>> WG6100's
>> design spec.)
>>
>> At the time I remember thinking that if you could essentially add a
>> hardware
>> wait state in the G-80 system vector generator when there's a long
>> beam jump
>> that it'd probably work 100%, but at the expense of a slight
>> framerate hit
>> possibly. If I ever explored that further I don't remember what
>> became of
>> it now. ;-)
>>
>> Zonn will probably know off the top of his head, but I don't think
>> it would
>> be any sort of bandwidth problem. I suspect it's just slew rate
>> limited
>> with the WG6100's lower deflection voltages. It would be
>> interesting to
>> find out if the WG6400 could keep up though.
>>
>
> Off the top of my head... Clay is correct. :-)
>
> The issue is vector drawing speed of the WG6101. The speed a vector
> can be drawn is dependent upon the voltage available and the
> inductance of the yoke. The bandwidth of the drive electronics, on
> both monitors, is way beyond being an issue.
>
> The WG6101 has a higher inductance yoke than the G08, and uses a
> +/-25V supply, it ends up being one of the slower vector monitors.
>
> The G08 has a fairly low inductance yoke and a high voltage supply
> of +/-50V (and also runs very hot, and originally shipped with
> underrated resistors that could catch fire). The G08 is pushing some
> design limits, especially the safe operation area of it transistors
> and the ability to keep them cool, hence the "wind tunnel
> heatsink". The G08's inductor is small enough that even running it
> at a lower voltage, it would still be fast enough to run any vector
> game built. Someone posted at one time (John Robertson maybe?) that
> they always set the voltage jumpers on the main transformer to the
> 130V settings (or whatever the highest setting is without jumping up
> to 200V range), that's really a good idea since since it's operating
> so close to it's limits, a 10% reduction in voltage would be really
> helpful.
>
> The thing about the Sega games is that the vector generator is not
> that fast (about the same as Asteriods), however it jumps very
> quickly between vectors, and that's the problem. Even though the
> WG6101 could easily handle the vector drawing speed, the Sega games
> don't wait long enough, when jumping between vectors, for the WG6101
> to make it to the start of the next vector.
>
> The frame rate for the Sega games is 40Hz, and the games don't use
> most of this time, they quickly draw the frame and then wait a the
> next 40Hz tick. If a wait state could be added between vector jumps
> it should work just fine and not have any affect on the game's frame
> rate, since there is a lot of idle time at end of a frame draw. This
> is why the ZVG can run Sega games at a full 40Hz on a WG6101, it
> just adds wait states between vector jumps, with plenty of time left
> at the end of the current frame and the start of the next.
>
> -Zonn
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Received on Fri Jul 17 01:00:22 2009