[time-nuts] Spectracom 8170 -> SWCC clock

Jim Hickstein jxh at jxh.com
Mon Jan 23 16:28:44 EST 2012

Reviewing the schematic for the 8170 (I'll get back to the setting coil in the 
clock a bit later), my unit does not seem to have Option 18 and A4-U4, the 8255A 
at its heart, is not populated.  A pity: it would have lovely BCD outputs and an 
on-time pulse, just what I need.  (The recent discussion of multiplexed 
7-segment LED outputs tells me I don't want to try to detect ":00:00" or 
":59:59" there.)

What are the chances my EEPROMs would DTRT if I just added an 8255A to this 
board?  What other components should I add to complete the Option 18 installation?

If I need different EEPROMs to enable Option 18, where could I get the image? 
(The parts and the programmer I can probably get.)

On 2012/01/20 16:23, Jim Hickstein wrote:
> I have a Spectracom 8170 in the living room (who doesn't?), and a Western Union
> time-service clock, a.k.a SWCC clock -- a nice one, in a 3-foot-high wood case.
> I've been watching TV with this combination for years and years but never got
> around to feeding a pulse from the 8170 to discipline the other one. Now that
> Western Union no longer provides the service. :-) But it just begs to be done.
> I did draw up a TTL circuit, once (on a napkin, naturally, which I have now
> misplaced), that could live inside the 8170. I figured out the minimum number of
> inputs needed to detect when the MM:SS LED displays said 00:00 (for one second).
> It would close a relay, which could feed the winding-battery power to the
> hour-set solenoid down a pair of wires from 10 feet away. But I never built it.
> A little over a year ago the TS clock was getting gummy and free-running slower
> and slower, so I sent it to the clock hospital. It's back and free-running
> nicely, so maybe it's finally time I did this. Anyone got a better idea than my
> little TTL circuit, on a breadboard inside the 8170? I'd like to get it across
> the rear panel without cutting a new hole, if I can avoid it. But maybe the
> right connector would do. Another time-code receiver in the TS clock, e.g. a GPS
> module that provides a relay closure for 1 second on the hour (if such exists)
> might be neater. But the living room faces north.
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