Display problem

[EEVaditya]

Hello,

 The seven segment displays(common anode) 4th,5th & 6th and 7th,8th &9th from right side are not showing the reading properly.
 
the problem I am getting is each of the above mentioned displays are showing same reading.

the displays are driven by IC's 7447 (SN74LS47N)

EEPROM is D2732A-2 (DIP-24)

the supply voltage is 5VDC

What would be the problem? refer attached photo.

[uncle_bob]

Hello,

 The seven segment displays(common anode) 4th,5th & 6th and 7th,8th &9th from right side are not showing the reading properly.
 
the problem I am getting is each of the above mentioned displays are showing same reading.

the displays are driven by IC's 7447 (SN74LS47N)

EEPROM is D2732A-2 (DIP-24)

the supply voltage is 5VDC

What would be the problem? refer attached photo.

Hi

What is the data on the input lines to the 7447's (pins 1 through 7) ?

Bob

[EEVaditya]

Hello,

 the data is in binary form, I dont have exact idea. but whenever I operate this pcb in machine it should display decimal readings but the problem is all the displays are changing simultaneously.for eg. it should show readings like 120,200,150 etc.but it is showing 777, 888 etc. please guide.

thanks.

[uncle_bob]

Hi

I suspect that ahead of the 74LS47 chips there is something like a 74LS75 / 74LS77 that holds the data to drive the 74LS47. There are at least two dozen different chip types that could have been used. It is impossible to guess all of them. The chip (what ever it is) acts as a memory for the display. It keeps the digits from changing like crazy. That chip has some sort of signal into it that tells it when to grab the data. If that signal line is shorted high, the memory chip will pass all the data instead of holding it constant. On the 75 / 77 the line to look at is called the enable line. It should be going high and low. If it is high all the time, you will get the display showing nonsense.

Bob