Re: Vector Hardware

Okay, now I am a bit confused.

I have laid my hands on one more board, which is the newer version, with only
half of the number of PROMS.

I suspect the DAC08 to be faulty (or circuitry around it) because my basic
picture is right (in the test screen with the large 'plus' sign, The AM6012 DAC
output is right (on my o-scope)) compared to that of a working board. However,
the DAC08 adds a signal causing the display to be offset and it shows a large
rectangle zooming in over and over.

But when I run this test on the older, working Tempest board, There is ONLY a
plus sign and NO zooming rectangle.
Also, when I check the DAC 08, it gets NO data on all its data lines, and adds
nothing to the output except the signal coming from the 'Vector' signal (added
throught the 2 transistors) but in the newer, defective board, the DAC08 is
feeded with data and I can see an extra square wave, increasing and decreasing
it's amplitude (And thus causing the rectangle I guess).

Is this normal (the linear and binary scale test maybe?) for the newer board or
is this just someting completely weird?

Jess Askey <jess@magenta.com> on 11/12/99 07:17:35 PM

Please respond to vectorlist@lists.cc.utexas.edu

To: vectorlist@lists.cc.utexas.edu
cc: (bcc: Mendel Pearl/Matra exiTel/nl)
Subject: Re: Vector Hardware

The DAC08 is performing the linear scaling for the vector generator. the vector
counter
can do the binary scaling (preset sizes). But if you want and object to change
size
gradually you need the linear scaling.
  If you watch the linear scale test, you see a box growing gradually out of the
center. I
think the way is works is that the output of the DAC08 is the input of the
AM6012's +ref
or something. Essentially, the DAC is a linear control of the XY DAC's positive
rail.
  If you watch the binary scale test, you will see the box jump from on scale
factor to
another. It can't do smooth scaling.

I did't thing that Tempest had linear scaling? Am I thinking of the wrong
DAC-08?

jess

Mendel Pearl wrote:
>
> Yes! Finally I got my Tempest AVG working again!
>
> The problem turned out to be the MC1495 multipliers, which was a real hard job
> tho find these here in Holland.
>
> My other Tempest board still has a problem with the X defection, the Y is
> working after replacing the current/voltage opamp (TL082) , thanks Rodger!
This
> little baby indeed caused the virtual ground to be not 'grounded' :)
>
> Maybe somebody could help me out on this one:
>
> What is the DAC08 doing in the circuit? So far as I can see from the
schematics
> and MC1495 datasheets, it seems to me that the MC1495 multipliers perform the
> east-west correction (pincushion).
> As you can see from the circuit, the output current of the DAC08 is directly
> summed to that of the XY DACs.
> Maybe somebody could shine a light here? I am really trying to know how the
AVG
> functions exactly...
>
> Thanks!
Received on Sat Nov 13 09:36:27 1999