Re: Cinematronic HV question

On Thu, 20 Jul 2000 17:28:29 -0500, you wrote:

>I've read Zonn's and David Fish's excellent Cinematronics monitor and HV
>troubleshooting guides. However, I have an 'early' Cinematronics monitor
>with the discrete HV section that resides on the monitor board itself.
>The HV has (surprise, surprise) stopped working properly, and while the
>later gold box HV modules are hard to find, the earlier ones are next to
>impossible to get.

        Ahhh, someone _else_ with a dead "first-generation" Cinematronics
monitor... I feel your pain. :)

>My tiny mind thinks all it will take is the removal of the now present
>HV components from the board, and a new set of wires and a molex
>connector to plug into the Keltron HV box. Is that it, and has anyone
>done this yet?

        I'd been thinking about this as well, actually, and your post prompted
me to track down some schematic sets for the different monitors, to see if
it's a feasable swap... Apparantly, there are _three_ different
Cinematronics monitor designs:

        (1) the "SPACE WARS"-style design, which uses the onboard HV section

        (2) an "enhanced" version of the above (used in "STARHAWK", and
possibly one or two others?) which has some additional circuitry in the
power-supply section. (I'm not quite sure what its purpose is yet, but its
a significant modification from (1). ) This design also has a 7805
regulator added, to generate +5V for the logic chips from the +25V input,
instead of relying on the +5V from the CPU board.

        (3) the "Keltron" design, which also has a somewhat different
power-supply section that's similar, but not identical, to (2).

        The DAC and deflection-driver circuits look the same across all three
designs, except that the "Keltron-style" schematic shows an empty space
where R122 and R222 used to be... These resistors were paralleled across a
.1uF capacitor and a 360 ohm, 1W resistor in series, and the whole trio was
paralleled across the deflection coil, like so:

(warning: ASCII art ahead!)

--------------------------o---------------------
                          ! !
(replace the _'s with ! !
 "1" for the vertical ---o--- !
 deflection circuit ! ! !
 and "2" for the ! ! C_02 !
 horizontal) ! --- 0.1uF !
                      ! --- 100V ----
                R_22 \ ! _)
                1.2K / ! _)
                1/2W \ \ R_23 _)
                 (?) / / 360 ohm )
                      ! \ 1W ----
                      ! / !DEFLECTION
                      ! ! ! COIL
                      ! ! !
                       ---o--- !
                          ! !
                          ! !
--------------------------o---------------------

        I can't imagine this has anything to do with the Keltron supply...
does anyone know what removing the 1.2K resistor from this circuit _does_
do?

        In any case - at _first_ glance, it doesn't look like the Keltron will
work as a drop-in replacement for the old-style HV section... but, now
that I have all three schematic sets in one place, I'm going to go through
them with a highlighter pen and see _exactly_ what the differences are; it
might actually be do-able with only a bit of tweaking. I'll keep y'all
posted. :)
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-----------------------------------------------------------------------------
solarfox@DON'TMESSWITHtexas.net (Gary Akins jr.)
http://lonestar.texas.net/~solarfox
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Received on Wed Aug 2 21:52:47 2000