Wong data for the Y DAC (Tempest)

Hi guys,

As you might have noticed, my Tempest board is still not functioning, so
I'll Give it a try here again...

Did anybody ever see that the XDAC was fed with the right data, but the
Y DAC with completely wrong data? (for example, in the large '+' test
screen, the X output shows correct,(a positive-negative going triangle
wave), the Y shows only one big positive going sawtooth).

I am sure the DAC's itself are OK, as well as the analog circuitry
around them.

My first guess is, that the cause could be the Vector Generator Data
Shifer circuitry. I believe this piece of hardware 'grabs' the X and Y
data from the databus, and thus could cause erratic Y data, and correct
X data.
Am I right here?

If ths is not causing the trouble, the data on the bus itself should be
wrong, but only for the 'Y' output. has anybody ever seen this before?

Is there theory of operation somewhere on the net, which describes these
digital circuits?

Thanks a lot guys!

Mendel
Received on Sat Nov 27 11:50:31 1999