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Old 26th Nov 2020, 1:40 pm   #27
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Join Date: Nov 2010
Location: Ross-on-Wye, Herefordshire, UK.
Posts: 1,356
Default Re: Racal Dana 9916 Frequency Counter.

Originally Posted by g0hze snowy View Post
Right Gents, some good news (for a change), i build Nixie and LED clocks when i am not playing with other things, to that end i have a number of nixie/led display driver ic's, so i dug out a 7447a ( see note from Richard above) and fitted that into the previously fitted ic socket, i was rewarded with a lot of 0's, so looking good, just have to wait for the correct ic's to arrive then i can re-assemble counter and give it a thorough check over.
So many many thanks to all that offered advice and suggestions. cheers, snowy

that's good news! I think it would be worthwhile though checking the voltages around that 7447A in circuit. Something caused that 74247 to fail (might be old age of course!), and there is at least one "odd" voltage - on pin 4. You measured 3.314V I think, which is neither a true LOW or HIGH. It would be worth checking with a scope to see what its doing now.

Also checking that all other pins are at either HIGH or LOW states - or have waveforms on them with those voltages.

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