RE: Atari STUNT CYCLE - service bulletins?

Yep, you're right, John. The trouble actually turned out to be a bit
upstream from that '193, a gate that provided the clock pulses to it. I
don't have my notes handy at the moment. I had schematics and two boards to
work with, and was fortunate to use both boards to locate the probelms on
each one. (And it seemed every time I let each board "burn in" for a few
hours, another totally different problem would crop up. Missing sounds,
motorcycle resetting to the middle part of the screen after a jump instead
of at the upper left, bad audio amp, etc. The +5 volt circuit was fine, but
these are 30+ year-old TTL chips...)

Come to think of it, one of big problems I had with one motherboard was a
bad 7402. It filled the entire screen with garbage, except for a small
window near the middle of the screen. The game was actually working okay
behind it, and periodically you could see the 'cycle whizzing past that
window.

It seems amazing to me how this game actually does what it does, considering
there is no microprocessor in it!
  -----Original Message-----
  From: owner-rasterlist@vectorlist.org
[mailto:owner-rasterlist@vectorlist.org]On Behalf Of John Robertson
  Sent: Thursday, August 05, 2010 11:00 PM
  To: rasterlist@vectorlist.org
  Subject: Re: RASTER: Atari STUNT CYCLE - service bulletins?

  Matt J. McCullar wrote:
    I worked on two motherboards for a _Stunt Cycle_ recently. Neither had
throttle problems. But one of them had a big problem: the black ramps
weren't present! Instead of the cycle jumping over the buses, it would just
repeatedly smash into them! ("Super Dave" _Stunt Cycle_! Very rare!)

    Matt J. McCullar
    Fort Worth, TX

  Hi Matt,

  As I recall the ramp info is put into a 74193 around the middle of the
last page of the three pages of schematics (/ramp and ramp). If you have a
Video Probe you can put the ramp development circuitry results directly on
the Monitor screen and figure out where it breaks down.

  You do know how to make a Video Probe, don't you? Check out the Atari Big
Book or any B&W Atari operator manual for details. Video Probing is a very
fast way to troubleshoot B&W not CPU based games (most times).

  John :-#)#

--
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Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
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