Re: Cinematronics monitor help

From: Zonn <zonn_at_zonn.com>
Date: Wed Mar 06 2002 - 16:16:42 EST

Tom M. just reminded me that I never got back to the list on the software I
mentioned below.

I gave this some thought and came to the conclusion that this software test
would be a bad idea.

Ok, let's say you have a monitor popping breakers. This software would allow you
to disconnect the power transistors and see if everything ran ok without them.

But what are the possible problems for blowing a breaker?

  1) Bad power transistors.
  2) Bad LF13331
  3) Bad DAC80
  4) Bad CPU board drivers
  5) Bad voltage regulator
  6) Bad built in HV unit

There are assuredly more things than that, that may cause a breaker to pop.

But just using the above reasons as an example, only #1 would be found by
running this test.

But if 2, 3, or 4 and possibly 5 were the problem, the CRT trace is going to be
sent to the extreme edges of the screen regardless of what the software test is
trying to display, and that's going to burn up a pre-driver transistor/resistor,
and now your going to have two problems, the original and the one just created
by removing the power transistors and running the monitor.

Those aren't very good odds for this test. And if the test is available, I think
many people that are at that "I'll try anything" stage of debugging, are going
to run this test and have 4 out of 6 chance of doing further damage to their
monitor.

I don't want to be associated with debug software that destroys monitors with
those kind of odds. ;-)

-Zonn

On Sun, 24 Feb 2002 21:33:43 -0800, zonn@zonn.com wrote:

>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 Wed Mar 6 13:18:18 2002

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