Note to those building an Exorcisor....anyone?

Hi Folks,

  Well I got my Exorcisor built and working yesterday and
discovered something important that I think is worth mentioning.
On the schematic there are two capacitors, both 220pF, shown
at the CLOCK input after the 100 ohm resistor. With either of
these capacitors present in the circuit my exorcisor would
not work, the clock signal was degraded to the point where
it couldn't reach Vih(min). I removed both and it worked
like a charm. I recall that Steve's unit would load the clock
signal down to about 2.5-2.7V, just enough still to work tho'.
I suggest removing them from the design.
  I also added an internal clock oscillator for self testing
and a simple clock detection circuit/indicator along with a
+5VDC LED indicator. It turned out that they were well worth
the little extra effort to put in. The clock detector is just
a 555 in astable mode that is triggered by the START/STOP
signal. The oscillator was one of those DIP types at 1MHz.
  I hope have a tech note finished next week which will show
how to debug the Line Length circuit which has that pesky
feedback. It will probably be after Thanksgiving.

David Fish | "We want...Information. INFORMATION
Melrose, MA USA | You won't get it!
   fishd@tiac.com | By hook or by crook we will"
   dfish@bev.etn.com | _The Prisoner_
Received on Fri Nov 21 15:16:52 1997