source for CA3161 (or NTE2032)

[Chris Iwata]

Big trouble: CA3161 is obsolete as others have told you.
 
But, if you're willing to do surgery you can substitute a 74LS47 which  is 
still available.  Difference is CA3161 has constant current outputs, set  at 
25mA  per segment  (wow that's high!): 74LS47 has no limiter, so  you'll need 
resistors to set the current for each segment. Typical LED  diode drop is about 
1.7V, so for 20mA you'll need 150 ohms per segment.   That is, you'll need 7 
resistors per digit.
 
You can cheat and just use one 150 ohm resistor on the anode.  The  
brightness of the digit will then vary depending on how many segments are  lit.  But at 
least it will work and you won't have to junk  the equipment.
 
Pinout is identical except 74LS47 has some extra inputs.  Pins 3,4,5  on 
CA3161 are NC. On the 74LS47 you will have to tie these  high. 
 
Get the datasheets for both ICs, still widely available of the web, you'll  
se what I mean.  That's how I figured out the solution.
 
Good luck,  Chris KL7DM
 
 



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