I've never tried hooking up a cinematronics game up to an oscilloscope in
XY mode.
Anyone care to explain where the X Y and blanking points might be? Can
you hook this up directly from the CPU board? I always thought it would
have to be done from the monitor since that's where the digital/analog
circuits are - which would probably be a waste of time since the purpose
of the oscope would be to take the monitor out of the troubleshooting
equation.
Ya caught my attention here.
Matt
_____________________________________________________________________
On Tue, 21 Dec 1999, Simon Whittam wrote:
> When I started collecting the first deal I made was with
> Dave Whitman in NC. I drove a cube van down there from
> Ottawa and picked up five VECTOR games. Luckily for me
> I had business in RTP and convinced my management that
> the cube van rental would cost the same as the return first class
> air tickets. That was two years ago.
>
> Since then the Asteroids, Asteroids Deluxe, Battlezone,
> Armor Attack UR have been working on and off but for the most
> part were all easy fixes (LS191 counters in the Asteroids, ROM
> reseating in the AST DEL, cap kit in the BZ and ROM reseating,
> and power supply repair (723) in the AA).
>
> The fifth game was a Armor Attack CT which he gave me for
> $50US (complete with extra boards but not working). This has been sitting
> in my
> basement for all this time and was dead until a couple of days
> ago. Cosmetically it is very nice (8+/10 with some glass scratches) and
> since I had never seen one
> of these before it seemed like a good deal (similar one on Ebay recently was
> about $600US??).
>
> SYMPTOMS: No picture. CPU board known good. PSU tested good.
>
> Fix #1: Replaced blown 47ohm resistor and 2n5320 in vertical drive (R118,
> Q108).
> Fix #2: HV supply needed replacing (no voltage).
> Now I get a long (length-wise) line on the display) => vertical
> deflection
> still not working.
> Fix #3: Replace heatsinked power transistors 2N5878/76 and pre-drivers
> 2N5320/22.
> [Unfortunately these tested well in and out of circuit and were only
> found bad by
> guess-work and substitution]. :-(
> Now I get a half-screen (top only) squished squiggly picture (made
> of segments) which
> seemed correct horizontally but zigged-zagged vertically downwards
> from the drawn object.
> Fix #4: Now I get the scope out and check the DAC output at the TL081s. I
> see a perfect copy of the game in XY-mode (comparing outputs of
> TL081s) so I know the DACs/analog switch
> and op amps are working OK. Using XY-mode to debug an XY monitor
> ... go figure?
> Fix #5: I go to the collector of Q104 (vertical) and keep the scope in XY
> mode (knowing
> that the horizontal circuit is OK). And the scope shows me the
> exact image that
> the monitor is displaying (though R-L inverted). Woo hoo!!
> Something is wrong at this part of the amplifier.
> NOTE: Schematics note that shown waveforms at TL081/Q104 etc are
> with Yoke removed ... I didn't bother doing that.
> Fix #6: Replace Q104. Tweak the gain and linearity POTs. Now she works
> perfect!!
>
>
> SUMMARY: Using the oscilloscope through the circuit in XY mode might help
> you to
> debug the monitor faster than a one-by-one point-by-point pin-by-pin
> analysis.
>
> Turned out to be a pre-Xmas present to myself (two years after the fact I
> guess).
> I hope this helps someone else fix their VectorBeam/WG XY monitor one day.
>
> SPW
> Kanata, On
> CANADA
>
> p.s. The CT monitor is nice a crisp on all drawn vectors. My UR monitor,
> however,
> has the player tanks kinda fuzzy. Any ideas what causes that? The text
> and 'copter
> are cleanly drawn.
>
>
Received on Tue Dec 21 13:35:00 1999
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