Re: [ukvac] TECH: Asteroids - LONG
I've been struggling with the Asteroids board for over a week now, but I
think I am close to fixing it. If you remeber I had a problem in the video
output circuit. All voltages are present and correct. I've also replaced
the TL082s and the 4016Bs. I no longer get a postage stamp sized image,
it's more of a large dot now! Using the scope I can get a Asteroids picture
before the 4016Bs but not after.
Anyway, using a working Asteroids board as a reference I've tracked the
problem down the the SHCON signal coming into the 4016Bs. I get a 3Mhz wave
on the working board and a rather strange looking signal on the none working
board.
Tracing this signal from the Vector Generator Circuit into the Video Output
circuit at R114. On both boards I get a 1Mhz square wave (3v point to
point) on the Vector Gen side. On the working board I get the same signal
(reduced to 1.5v point to point). But on the non-working board the signal
has been lost. Something is killing the signal. I don't believe the
problem is the R114 as this reads fine on a meter.
Now there seem to be several components between R114 and pin 12 of the
4016Bs. The Atari schematics I have don't show any of these. I guess one of
these could be at fault or it could be the capacitor (of unkown value) in
parallel with the R114. But without component level schematics it's
difficult to continue the diagnostics.
Does anyone have any idea what could be causing this? Alternatively anyone
have any schematics that show all of the components in this part of the
circuit?
Cheers,
Steve
>From: "Steve M" <marog_uk@hotmail.com>
>Reply-To: ukvac@yahoogroups.com
>To: ukvac@yahoogroups.com
>Subject: [ukvac] TECH: Asteroids
>Date: Sat, 16 Feb 2002 13:04:54 +0000
>
>I've got an Atari Asteroids board that produces a display image the size of
>a postage stamp!!! I have tried adjusting the X & Y pots but this makes no
>difference. It's not the 19" monitor either as is works fine with an
>Asteriods Delux board.
>
>The image produced is about 1/2" by 1" and appears on the left, center of
>the display. You can just make out the asteroids, ships etc. in game mode
>and the criss-cross pattern in test mode. I connected up a scope to try
>and
>amplify the small signal being generated, but couldn't get a stable image.
>
>There is no sound either in game play mode - but I do get bleeps when I
>push
>buttons in test mode.
>
>I looked at a couple of 'Asteroids' trouble shooting websites - but nothing
>like this is ever mentioned. I suspect it is something to do with the
>Vector generator / amps - but don't really know where to start looking.
>
>Anyone seen this problem before? Can anyone give me some pointers to which
>components to test/replace?
>
>Cheers,
>Steve
>
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I've been struggling with the Asteroids board for over a week now, but I
think I am close to fixing it. If you remeber I had a problem in the video
output circuit. All voltages are present and correct. I've also replaced
the TL082s and the 4016Bs. I no longer get a postage stamp sized image,
it's more of a large dot now! Using the scope I can get a Asteroids picture
before the 4016Bs but not after.
Anyway, using a working Asteroids board as a reference I've tracked the
problem down the the SHCON signal coming into the 4016Bs. I get a 3Mhz wave
on the working board and a rather strange looking signal on the none working
board.
Tracing this signal from the Vector Generator Circuit into the Video Output
circuit at R114. On both boards I get a 1Mhz square wave (3v point to
point) on the Vector Gen side. On the working board I get the same signal
(reduced to 1.5v point to point). But on the non-working board the signal
has been lost. Something is killing the signal. I don't believe the
problem is the R114 as this reads fine on a meter.
Now there seem to be several components between R114 and pin 12 of the
4016Bs. The Atari schematics I have don't show any of these. I guess one of
these could be at fault or it could be the capacitor (of unkown value) in
parallel with the R114. But without component level schematics it's
difficult to continue the diagnostics.
Does anyone have any idea what could be causing this? Alternatively anyone
have any schematics that show all of the components in this part of the
circuit?
Cheers,
Steve
>From: "Steve M" <marog_uk@hotmail.com>
>Reply-To: ukvac@yahoogroups.com
>To: ukvac@yahoogroups.com
>Subject: [ukvac] TECH: Asteroids
>Date: Sat, 16 Feb 2002 13:04:54 +0000
>
>I've got an Atari Asteroids board that produces a display image the size of
>a postage stamp!!! I have tried adjusting the X & Y pots but this makes no
>difference. It's not the 19" monitor either as is works fine with an
>Asteriods Delux board.
>
>The image produced is about 1/2" by 1" and appears on the left, center of
>the display. You can just make out the asteroids, ships etc. in game mode
>and the criss-cross pattern in test mode. I connected up a scope to try
>and
>amplify the small signal being generated, but couldn't get a stable image.
>
>There is no sound either in game play mode - but I do get bleeps when I
>push
>buttons in test mode.
>
>I looked at a couple of 'Asteroids' trouble shooting websites - but nothing
>like this is ever mentioned. I suspect it is something to do with the
>Vector generator / amps - but don't really know where to start looking.
>
>Anyone seen this problem before? Can anyone give me some pointers to which
>components to test/replace?
>
>Cheers,
>Steve
>
>_________________________________________________________________
>MSN Photos is the easiest way to share and print your photos:
>http://photos.msn.com/support/worldwide.aspx
>
_________________________________________________________________
Send and receive Hotmail on your mobile device: http://mobile.msn.com