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shermaine said:As Eric told you, you should connect 100 nF capacitors between pins 7 and 14 on U1, U2. U3, U4 & U6 and across pins 8 & 16 of U5 and a 100 uF acroos the supply line.[I never connect any capacitors as i got no capacitor now] This may be a problem when the counter is working. You should get some capacitors as soon as possible.
Connect a 5 Volt supply.
Does the circuit now work? [No]
If not, turn the power off and remove ICs U4 & U5.
With switches S0 & S2 off, the green LED should blink at the oscillator rate.
[Green Led Light up] Is the oscillator oscillating, if so at what frequency?
If so, put a gnd on pin 12 of the U5 socket and the red LED should blink.
[Green Led light up] Have you changed ICs U2 and U3, they may have been damaged by the 9 Volt? This is strange given the answers below. Do this again and measure the voltgae on the output of U1c, it should be high since U5/12 is low. If so, measure the other inputs to U2a and the output of U2a.
If so, leave the gnd on pin 12 and put a gnd on pin 6 of the U5 socket, switch S0 on and the red LED should blink. [Red led light up] Good. /COLOR]
If so, leave the gnd on pins 6 & 12 of the U5 socket, switch s2 on and the green LED should blink. [Green Led light up] Good. This together with your previous answer tends to indicate that U2 & U3 are OK
If so, turn the power off, remove the gnds from pins 6 & 12 and plug U5 in.
Switch the power on and see if U5 is counting. [not counting] It may be damaged, did you change it for another one?
If so, turn the power off and plug U4 in. [not counting]
Turn the power on a see if the circuit works.
These tests should help you to locate where any faults are.
For example, if U3 is damaged, either the LEDs will not go on when they should or may be permanently on.
Can advise which part that is having fault? Thanks a million!!
NAND and NOR gates have advantages over AND and OR gates.shermaine said:Hi,
I have managed to change 74191, but the output still the same. did u see my redrawn ic pin layout, is there any connection wrong with the dip switch. And one thing about your kanaugh map, i was wondering how come you are using nad gate and not and gate?
shermaine said:Hi there,
If so, put a gnd on pin 12 of the U5 socket and the red LED should blink.
[Green Led light up] Have you changed ICs U2 and U3, they may have been damaged by the 9 Volt? This is strange given the answers below. Do this again and measure the voltgae on the output of U1c, it should be high since U5/12 is low. If so, measure the other inputs to U2a and the output of U2a.
Pin 8 of 7400 is 4.4V and pin 8 of 7410 is 0.09V and pin 9 of 7410 is 1.47V.
Seem like U2a is damage, right?
Please advise. Thanks.