Re: Asteroids X axis problem

no schems to hand here, but i would suggest checking the +/15v DC when the
sizing pot is at minimum and at maximum. I would do the same for the +/-6.8v
Zeners (i've had similar results with zeners)... they key here would be to
observe reference voltages on a scope while adjusting the pot and look for
anomolies. Same for almost anything else, you should see where the
distortion starts along the chain, using the y-axis as a working reference
circuit for how things should act when the pot is adjusted.

My gut feeling on this fault is one of the TL op-amps failing marginally, or
losing its reference voltage somehow.

----- Original Message -----
From: <arcaderelics@irongiant.org.uk>
To: <vectorlist@vectorlist.org>
Sent: Saturday, March 13, 2010 1:39 AM
Subject: Re: VECTOR: Asteroids X axis problem

>
>>If adjusting the x-axis size changes the results then the problem area is
>>around the X-Axis size control and related ICs or later (no schematic on
>>hand).
>>
>>You did say that you tried a later board and no problem on the monitor -
>>that lets the monitor and power supplies out.
>
> Indeed. I'll either put up with it (and simply reduce the screen size a
> bit) or swap out a few more parts.
>
>
>
> Ta for the advice. :-)
> Phil
>
>
>
>>>>Do you have a picture?
>>>
>>>Afraid not, not much to see really though, just a vertical line the
>>>height of the object as it passes through the edge of the screen (the
>>>object is still drawn okay though).
>>>
>>>
>>>Thanks,
>>>Phil
>>>
>>>
>>>
>>>>
>>>>-Mark
>>>>
>>>>
>>>>
>>>>Just been fixing up my first Asteroids board for ages - multiple
>>>>problems, all now fixed ......... except for one.
>>>>
>>>>Whenever an object gets to the far left or right edges of the display
>>>>it's still drawn okay BUT as the object passes through the edge it makes
>>>>a vertical line at that edge where the object is passing through - the
>>>>line is same 'height' as the object too.
>>>>
>>>>Now I've seen something similar before which was caused by a problem
>>>>with the UNMDACX12 signal, but in this case that's not the problem as
>>>>changing the relevant chips (7404 at H10 and LS191 at C9) doesn't fix
>>>>the fault.
>>>>
>>>>This is an early Rev 2 board.
>>>>
>>>>Could of course be the AD561 DAC, or the TL081 or TL082 in the X axis
>>>>output circuit, but is there anything else that I've missed before I go
>>>>swapping out multiple chips? I can't unfortunately see any faults when I
>>>>'scope out the signals.
>>>>
>>>>
>>>>Thanks,
>>>>Phil
>>>>
>>>>
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>>
>>
>>--
>>John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call
>>(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
>> www.flippers.com "Old pinballers never die, they just
>> flip out"
>>
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>
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Received on Fri Mar 12 19:53:34 2010