Re: [stella] administratia and phrack!

Subject: Re: [stella] administratia and phrack!
From: Chris Wilkson <ecwilkso@xxxxxxx>
Date: Fri, 17 Sep 2004 15:07:26 -0400 (EDT)
> phrack:
> I think I fried my TIA.  Poking around things with a o'scope, I may have
> accidently shorted out Phi2 to either +5V or GND.  Gotta be careful
> with those probes.  No more clock signal.  Before I shorted it out,
> I got to look at it.  Definately NOT a square wave.  Reminiscent of
> capacitor charge/discharge.  Almost a sawtooth.  Am I doing something
> wrong, or were those things really that dirty?  I'm used to square waves
> with nice pretty sharp edges and almost no ring.

The short of it...the clocks are ugly.  OSC is not really capable of driving
more than just the single TIA input.  PHI0 is generated by the TIA.  It's
decent.  PHI2 is generated by the 6507.  It's decent, but you don't want
to hang a big scope probe off of any of these.  Some probes are pretty
capacitive.  And make sure your scope probes are calibrated for your scope
and the the scope and the probes both have the bandwidth to handle 5 MHz.
(pretty unlikely that they're too slow, but...)

Oh yeah.  By "decent" I mean it's not a perfect square wave, but it's pretty
good.  Much closer to an ideal square wave than a sawtooth.

Best not to think about it.  :P

Now how's some debugging info for you.
(The following assumes that something actually blew up.)

Is OSC still ok?  (TIA pin 11 - input)  If not, you blew the oscillator.
Is PHI0 still ok? (TIA pin 4 - output)  If not, you blew the TIA.
If OSC and PHI0 are both ok, you blew the 6507.


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