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I'm trying to play with CD4026BE counter and I'm unable to solve the problem with reset pin (15 according to datasheets and numerous examples). In my case, if pin 15 (reset) is grounded with the wire, the counter works perfectly. Otherwise this pin outputs (!) 5V voltage! If it is grounded, through this pin flows a significant current of 50mA, which is way too much in my opinion. Any resistor between this 15 pin and ground, as suggested everywhere, keeps high voltage on this pin and prevents the counter from counting. I'm at a loss, since in every example I see, people send HIGH signal on pin 15 to reset it, but it is already high in my case. I've searched "4026" questions here with no result. Indeed, no evidence of a similar problem. Could i have missed anything (quite possible, since I'm only starting to learn electrical engineering)?

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  • \$\begingroup\$ Are you absolutely sure you're counting the pins correctly? \$\endgroup\$ Mar 2 '15 at 18:18
  • \$\begingroup\$ I am now, but I must have at some point made a mistake and faulted both CD4026BE I was playing with. Fresh ones work as expected. \$\endgroup\$ Mar 3 '15 at 17:39
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I see one of two possibilities.

1) The ground pin of the chip is not connected to ground. Check that pin carefully to make sure that it actually goes to your power supply (-) terminal.

2) The chip is faulty. The reset pin might have seen an over-voltage excursion which destroyed the internal protection diode between the pin & Vdd. Your only option in that case is to replace the chip.

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  • \$\begingroup\$ The chip definitely is faulty, as i know it now. What dismayed me, is that I had two faulty chips :). I must have at some point connected the scheme wrong, - for example I knew nothing about the danger of supplying inputs before attaching Vdd. Replacing two chips I could have falted them both. Trying with the fresh one today with the same connectings made it all work perfectly as expected. Even more, one of the yesterdays chips must have recovered :). While the second one still outputs 5V to pin 15. Thank you very much for your hints! \$\endgroup\$ Mar 3 '15 at 17:33
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There is clearly something wrong. There is no way you should be pulling more than a few microamps when you ground the pin.

My best guess is that either you have a defective IC, or you have inadvertently connected pin 15 to its neighbor, pin 16 (Vcc).

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