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Two identical circuit boards, one working one not

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wars0696

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I have two identical circuit boards using IC MM74HC123 one manufactured by Fairchild Semiconductor the other by Philips. The Fairchild chip when used in the circuit will announce any length of message the Philip circuit won't announce the longer messages. I don't have a circuit diagram for the board. I only difference on the datasheet is differences in the propagation delay, output transition time and power dissipation capacitance. Could anyone please tell me which of these would course the problem and why?
 
I have two identical circuit boards using IC MM74HC123 one manufactured by Fairchild Semiconductor the other by Philips. The Fairchild chip when used in the circuit will announce any length of message the Philip circuit won't announce the longer messages. I don't have a circuit diagram for the board. I only difference on the datasheet is differences in the propagation delay, output transition time and power dissipation capacitance. Could anyone please tell me which of these would course the problem and why?

I have seen this problem before, the Philips ic's have a different Res/Cap time constant value for monostables.. it could be related.:)
 
hi,
Look at this image, explains it.
 

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