Reply to "Semaphore and 555 Timer Circuit"

rtr12OGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

Finally got around to assembling one of the dual mode CA-CC PCBs using the 74AC86 ICs. So far it is a fail, nothing works on the traffic light outputs in either CA or CC mode. I can't seem to find anything wrong in the wiring traces on the PCB or in the schematic?

One thing I found odd: there is only about 1.1 volts on the 4017's VDD pin when the PCB is powered up. When I remove the 4017 from it's socket and power the PCB the VDD pin (on the socket only) has 5 VDC where the 4017's VDD pin should be.

I've probably goofed up something, but what? Back to 'sits and thinks' at the work bench...

8/29/194:54 PM

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