Re: Tech: Cinematronics Monitor

Hi Keith!(And others)

The thing to remember about these (and other vector monitors) is they
are basically just audio amps with attitude (they want to be in
pictures).

You can run these with the YOKE unplugged! This will put a no-load
situation on the output transistors and you will not smoke any parts
when testing. You must NEVER unplug the output transistors on any
monitor and then provide power, this will do serious damage to your
wallet. Now that you have the yoke unplugged you can 'scope the signal
to the yoke and see if the average signal is at zero volts. That is the
+ and - signals hover evenly relative to the 0 level. This assumes you
have a working board. With a no-signal situation, and inputs grounded
the output to the yoke should be zero volts.

Now, if I had time, I'd go into how to make simple signal inputs to test
your monitor, but, now that you have a clue (audio amp) perhaps you can
figure out your own. Remember that the input is about 1VPP and these are
essentially stereo...

Vectorbeam/Cine monitors, well, a switch box that has pullups and other
riff-raf comes to mind...play with the LSB's first...get a scope...A/D
convertor...

John :-#)#

Keith, Brendan wrote:
>
> Is anyone familiar with common failure modes in a Cinematronics monitor?
> I have an Armor Attack (and a few other boards to test) and this recently
> traded monitor will not stay active. It constantly trips the +25V breaker
> in
> the power supply.
>
> I have disconnected the Keltron HV unit, so it's not that. I measure good
> voltage on either side of the 7815 before the breaker trips (about 1-2
> seconds).
> The digital cable is disconnected so it's not trying to deflect.
>
> I wouldn't expect the DACs or LF13331 (is that just a quad switch, like a
> 4066)
> to draw enough current to trip the breaker. Or the op-amps.
>
> After closing up shop last night and thinking about it some more I figured
> maybe one of the deflection transistors could be shorted but the manual says
> not to run the monitor with them disconnected. Is that because the
> deflection
> driver transistors would then try to drive the deflection yoke directly? I
> have the schematics
> in front of me, but I'm a little more familiar with the digital domain
> rather than analog.
>
> Is it safe to disconnect the deflection yoke alone? Then the deflection
> transistor pairs?
>
> Thanks to all, in advance.
>
> Brendan Keith
> brendan.keith@wilcom.com
>
> P.S. Don't suggest a freakin' cap kit! Sheesh! ;)

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