Software Counter/Oscillascope

[danial stocks]

Sorry folks been on hols, missed the start of this thread.. but anyway, mem 
probs can be the mem chips themselves.. I've seen the upd 444c's blow out 
before.. replacement with 2114 is pin compatible but draws too much current 
for mem retention, there are a few obscure other ones which could be used 
tho UM6104 can I think, altho I spliced in a 6116 when I had to fix this, it 
actually fits one 6116 in the socket over the 2 memchips original spots.. it 
hangs off one end, the unused datya lines, which you terminate in a res 
network to gnd.. I think one other pin needs to be changed, but its a 1 chip 
replace, no glue logic, and you get an extra mem bank as a bonus!..
Cheers,
Dan
> >I've been over the circuit board dozens of times checking 4 broken
> >traces and the such, tested 100's of parts, but with no avail.
> >The last thing that i feel sus about in this unit is maybe the CPU
> >clock and/or "INT Clock" (is this interupt clock?) is mis aligned.
> >The "Int clock" adjustment is made via trimmer TM1 while the CPU is
> >one of those tuning coil "thingie majigs".
> >I asked this question on AH with no responce about what the symtoms
> >of an mis alligned CPU clock and INT clock would be in an XOX
> >machine???
>
>I seem to recall that the int clock is being used to do the panel scanning.
>Every 1.8 mS, it tells the processor to try to look at the next group of
>buttons.
>
>If the clock were misaligned, there might be two different scenarios.  If
>the period were too long, it wouldn't be watching the buttons as often, so
>it might seem a little sluggish or unsreponsive when you push buttons...but
>I'd venture a guess that it's have to be significantly slower than 1.8 mS.
>
>If the clock were faster, yopu might find that buttons didn't register,
>because the scanner would move on before the contacts on one button were
>done bouncing.  I think that if the Int clock is sick, the switch scanning
>will be sick.
>
> >I've been working 4 a couple of weeks now on a non funtioning 606,
> >all the sound generators are fine, yet it refuses to write anything
> >to memory (playing previously stored patterns and tracks work
> >though).
> >this might not be the case as it has no problems playing back
> >previously stored patterns and tracks, just anything involving
> >writing to memory.
>
>Check the health of the "-WE" lines to the Ram chips.  When you're writing 
>a
>pattern, those lines should be hopping up and down a bit...of course 
>without
>a scope, they'll be very hard to see...those cycles are probably darned
>quick...guessing somewhere in the 1 or 2 uS range.
>
>Even if you don't have a scope, at least check the continuity between them
>and the glue logic that generates -WE...and then from the glue back to the
>processor.  It could be that the Glue is dead...assuming all of the above
>suspects are getting power.
>
>Byron Jacquot
>

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