Re: Differences between SG1495N, MC1495L, and MC1495P?

><< 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 >>
>
>Ha! This is great! Thanks Zonn, I have a better understanding now.
>I understand the MC1495L is a slower multiplier than the MC1495P or
>SG1495N.
>I was curious as to what boards actually used the MC1495L??

Actually guys, the 1495P and 1495L are the same. It's a package different.
(L are ceramic dip, P are plastic dip)

The MC1595 is a "better" version of the 1495, but given what it's used for
in the Atari games it won't matter. The SG1495 is a direct replacement.
You can freely mix and match MC1495/L/P, MC1595/L/P, and SG1495's.
Sometimes you see "N" as a suffix for plastic packages. (Signetics liked to
use that one insead of "P")

Way back when I did the WG display correctors I wrote up a very detailed
explanation of what the 1495's do in Tempest/SD/etc. It was either posted
to Vectorlist or RGVAC, but I didn't keep a copy (sorry). It described the
constants and equations that the 1495's are actually carrying out in analog
form.

(Off the top of my head though, one is used to square in the input voltage
resulting in an always positive value proportional to the Y axis deflection.
  That in turn is fed to the second set of multipliers that multiply that
times a second fractional number [<1.0] which results in something of a
"ramp" vs. the input voltage and thus helps "uncurve" the output a bit.
There's some size and linearity control done with op-amps too. The VDR
seems to help "de-linearize" the ramp a bit, although I never paid a whole
lot of attention to it in particular.)

So, if you plug in an MC1495L and it doesn't work, but a MC1495P does-- it's
a bad MC1495L. ;-)

Happy Holidays,
-Clay

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Received on Fri Dec 29 01:39:10 2000