Re: Asteroids Deluxe 12.096MHz xtal

New problem :(

I put the 12 MHz xtal in, voila.... the screen came up. Unfortunately,
everything is mirrored left-right (Obviously, the game is mirrored so if you
look directly at the monitor, everything is in the correct orientation...
know what I mean?) I hooked my o-scope up to the X-Y outputs of the AD PCB
and it shows up as not-reversed... incorrect. Also, no input is being
registered from the control panel or the coin door... What could have
happenned by plugging in this alternate PCB???

----- Original Message -----
From: Clay Cowgill <vector_clay@hotmail.com>
To: <vectorlist@synthcom.com>
Sent: Thursday, January 13, 2000 5:38 PM
Subject: RE: VECTOR: Asteroids Deluxe 12.096MHz xtal

> >I've also got a question about ordering crystals. I usually order my
parts
> >from Mouser and in their catalog, most of the crystals have two choices:
> >series or 20pf. Which one should be used on Atari boards or does it
really
> >matter?
>
> I'll take a shot at this, but I can quickly get out of my depth on this
> analog stuff, so anyone else feel free to correct me if I'm wrong. ;-)
>
> Crystals are usually specified as being either Series or Parallel
resonant.
> Some will also operate in fundamental mode, or an "overtone" mode (a
> harmonic of the fundamental frequency).
>
> Generally speaking, most crystals under 20MHz are probably fundamental
mode.
> (The frequency they run at is the primary frequency that the cut in the
> crystal achieves when current is passed through it.)
>
> Series mode crystals generally do not require any additional capacitance
to
> oscillate at their given frequency (they act more like a resistor
> electrically). Parallel mode crystals do require extra load capacitance
to
> oscillate-- the crystal acts more like an inductor in the crystal circuit.
> (The load capacitance is that 10-20pF you see in the catalogs-- it's
usually
> a little cap hanging off each leg of the crystal when you look at the
> schematic.)
>
> In a overtone-mode (non-fundamental frequency) there's usually another
> inductor in the crystal tank circuit that tunes the circuit off of the
> fundamental (and usually just over or under the desired overtone). This
> helps the resonance to start and selects the harmonic instead of the
> principle frequency. Overtone crystals are usually what you find for
> frequencies over 33MHz-- it can be tricky to design the tank circuit to go
> with them. Oscillators are a good choice if you don't want to deal with
it.
> ;-)
>
> Anyway, the good news is that most old games use relatively low frequency
> crystals, and for all intents and purposes you can probably get away with
> using either a series or parallel resonant crystal in an old game-board
> repair.
>
> -Clay
> ______________________________________________________
> Get Your Private, Free Email at http://www.hotmail.com
>
> --------------------------------------------------------------------------
-
> ** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in
the
> ** message body to vectorlist-request@synthcom.com. Please direct other
> ** questions, comments, or problems to neil@synthcom.com.

---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.
Received on Thu Jan 13 20:22:55 2000