Re: Cinematronics monitor help

On Sun, 24 Feb 2002 22:59:29 -0500, "Mark Jenison" <jenison@enteract.com> wrote:

>Hi all,
>
>I've got an early version Tailgunner monitor here. I was able to borrow a
>working Star Castle machine from someone and am using it as a test fixture
>for the Tailgunner monitor.
>
>Right now, the monitor stays up for about 10 seconds, with deflection
>chatter, no picture. Then the -25V breaker pops (then shortly after, the
>+25V breaker).
>
>Measuring voltages, all regulators are outputting the correct voltages
>(+/-18VDC, +/-15VDC). However, the +25VDC seems high (about 28 volts).
> The -25VDC is right on the money. However, when the -25 pops, the +25VDC
>line dips down to +25VDC.
>
>Unplugging the yoke and retrying, the breakers do not pop, and I get a nice
>white dot in the center of the screen.
>
>I've checked the tants, diodes and transistors; they all seem fine.

It sounds like you are only getting chatter in one channel, and that the other
channel is pegging the yoke to one side, causing the circuit breaker to blow.

Check the power transistors, using the standard diode setting on a VOM, and see
if any are shorted.

>BTW, the Cine monitor doc on spies says to unplug the harnesses to the heat
>sinks and leave the yoke plugged in to get "a smaller picture". I tried
>this once before I got this far and it burned up a bunch of resistors.

That is a really bad thing to do. Unplugging the heatsinks causes the full load
of the yoke to be handled by a couple of small pre-driver transistors through a
couple of 47ohm resistors (which is probably what you smoked before). Who ever
recommended this must have inhaled too much of that resistor smoke.

Now if there were some test software that generated a very small picture in the
middle of the screen, small enough as to not overload the small pre-driver
transistors and resistors, this could possibly be a valid test.

I'd have to look into the pre-driver current loads, to verify that a box small
enough to keep from overloading the pre-drivers, and yet large enough to be
useful, could be drawn.

If anybody is interested in such a program, I'm sure I could have it written by
the end of the week. (Given my current schedule.)

-Zonn
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Received on Sun Feb 24 21:32:33 2002