Re: Differences between SG1495N, MC1495L, and MC1495P?

Hi Matt,

I believe you are mistaking this chip for a different one. (However your
description of an analog switch and its characteristics, is a fine one.)

The 1495's are analog multipliers. They're 4 quadrant (meaning that multiply
all possible positive and negative input values with an output that can be
positive or negative.)

If I recall they are used in Tempest to adjust the size, and also (with the help
of a Voltage Dependent Resistor connected to the alternate X or Y channel) are
used to correct for a bowing/pincusioning effects of the WG monitors.

-Eroom Nnoz

On Wed, 27 Dec 2000 10:28:56 -0800, "Matt J. McCullar" <mccullar@flash.net>
wrote:

>
>>Hello,
>>
>> I recently had to replace an SG1495N in the Y output section of a
>>Tempest boardset. At first, I used a MC1495L, and the y output was too
>large,
>>even with the y-size pot turned all the way down. I then tried a MC1495P,
>and
>>the y output was great.
>> Can anyone please explian the differences between the MC1495L, MC1495P,
>>and SG1495N? Perhaps there are datasheets on line for these?
>
>
>I work with these chips frequently but don't have the datasheets handy at
>the moment (they're all at my workplace). Machine-tool industrial motor
>drive controllers use them in analog feedback circuits.
>
>The 1495 is an analog switch. When turned off, it prevents a signal from
>passing through it. When turned on, it lets the signal pass. The problem
>is, when turned on, the chip still presents a fair amount of resistance
>(load) to the signal. This amount of resistance is notoriously variable;
>not just from manufacturer to manufacturer, but also from one particular
>type of chip to the next from the same company.
>
>When I do static tests on these chips, sometimes I read 38 ohms or so.
>Sometimes its 50 ohms. Sometimes it's 68 or 70 ohms.
>
>Atari used these chips to invert (or NOT invert) the polarity of an X/Y
>video signal. When turned on by a TTL signal, the analog switch would turn
>on and would therefore re-route the video signal into an op-amp-based
>inversion circuit. This was done to "flip" the picture on cocktail games.
>I recently ran into a _Tempest_ board that had a problem with one of these
>analog switch chips; it always kept the picture flipped from left to right,
>so that instead of "GAME OVER," it always said "REVO EMAG".
>
>Sekips Diova,
>
>Matt J. McCullar
>Arlington, TX

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Received on Wed Dec 27 14:57:28 2000