Re: Cinematronics > Atari Adapter???

Gang,

This is what started my train on thought on the adapter again.

Here are screen shots of my only working monitor. Intersecting lines
don't meet - even in the screen with two verticals. The adjustments on
the chassis don't help.

http://photos.yahoo.com/bc/rgvac_macman/lst?.dir=/My+Photos&.view=t

I mentioned it to Zonn at CGE and he suggested it might be a yoke
incompatibility and maybe had a note of change of resistors that he
would look up. I written to Zonn directly but thought I might throw it
out here for people to have a shot at.

Anyone know what is causing this?

Cheers
Paul

On Tuesday, October 15, 2002, at 02:53 AM, Rodger Boots wrote:

> Tom McClintock wrote:
>
>> Well get right on that Rodger! :)
>>
>> Seriously, I was under the impression that the settling time for the
>> DAC was
>> determined more by the DAC than subsequent Op-Amps. The DAC7541 seems
>> to have a
>> settling time of 30 m sec, while the DAC-80s (or DAC7580) have
>> settling times
>> around 4 m sec.
>>
>
> Not sure where you got the 30 mS spec, the only settling times listed
> on the DAC7541 spec sheet are .6 uS typical for the output CURRENT to
> settle to .5 LSB. The opamp that's doing the current to voltage
> conversion will be the speed limiter. VOLTAGE output DACs are
> notoriously slower than current output DACs.
>
>> Unfortunately, even if the DAC was $11 each, you need two, plus the
>> supporting
>> hardware so your cost is running about $35 in parts alone (gotta
>> include those
>> connectors). A finished PCB would add another $10 or so. This gets
>> into the
>> realm of what a Cine monitor board costs (well, usually on the high
>> end as most
>> operators don't want these monitors at all).
>>
>> But I agree a 'new' Cine->WG conversion board would be really cool.
>> What's the
>> cheapest way to go with this?
>>
>
> The cheapest way? Build your own R-2R array and don't even buy the
> DACs. The way Cinematronics draws vectors (capacitor integration) you
> really don't need an accurate DAC. Probably don't even need 12 bits.
> All you're generating are start points and "end points" (not really end
> points, more like "it goes thisaway" points). A bumpy DAC won't matter
> because it doesn't draw the line in between the points.
>
>>
>> tm
>>
>> Rodger Boots wrote:
>>
>>
>>> You could use something like the DAC7541 which is under $11 even in
>>> single lots. The op-amp following the DAC will determine the settling
>>> time. Like Tom says, you can have the DAC only give a positive output
>>> (in this case by using a negative reference for the DAC) to allow
>>> cheap
>>> switches and subtract out the midpoint (using the same reference
>>> voltage
>>> for best results) to get the desired output swing.
>>>
>>> Really nothing much to it.
>>>
>>> Tom McClintock wrote:
>>>
>>>
>>>> Wait, here are some notes from Zonn.
>>>>
>>>> ------------------
>>>> Your biggest problem with doing a Cine->WG board is
>>>> that you are forced to use 12 bit parallel DACs, which
>>>> are expensive. The Cine design is pretty much going to
>>>> force you to find ~1 to 2 us settling time parts. (To
>>>> keep the frame rate up, we had to do the same.)
>>>>
>>>> Though you might be able to save some money by using
>>>> single supply 12 bit DACs and shifting the voltage
>>>> after the analog switch / RC stuff. This is the
>>>> approach we took in the ZVG. This also allows the use
>>>> of the much more available and less expensive 74HC4066
>>>> switches which are only single polarity switches. The
>>>> LF13331 were bi-polar, and also expensive (when they
>>>> were available).
>>>>
>>>> You can't use serial DACs. They would require a
>>>> parallel to serial conversion and there is no time
>>>> allocated in the hardware to allow this. The DACs are
>>>> latched and the Z-axis is turned on for the draw,
>>>> there's no "clock data into DACs" time, which at
>>>> minimum would take 16 clock cycles, if both DACs were
>>>> simultaneously clocked.
>>>> -------------------------------
>>>>
>>>>
>>>> Beyond that, lemme know if you come up with something :)
>>>>
>>>>
>>>> tm
>>>>
>>>>
>
>
>
>
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Received on Mon Oct 14 12:50:09 2002