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74HC4511 BCD problems

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Hi all,


I picked up some CD74HC4511 binary to decimal converters to use with my 7 segment displays, however I'm having some issues with them.


The problem I'm having is some decimals fail to fully display, for example:


I'm sending 0100 (d3 low, d2 high, d1 low, d1 low), that should display a 4, however the G segment on my display is not lighting up, when probing the G LED's pin I'm getting 1.8v, I'm also getting 1.8v when I probe the F pin, pins D and E are 0v as expected, pins F, B and C are 3.5v as expected.


Similar things are happening when trying to display the decimal 6, all have their expected voltages, accept the G segment whitch is reading 1.8v.


I'm really stumped as to what is causing some numbers to not properly display and the random voltages.


Heres the datasheet:



Here is the circuit I've been using for testing:

http://hs.doversherborn.org/hs/bridgerj ... addLED.htm



The only minor differences I have are that I'm using 5k resistors (out of 10k's, but according to my googleing, 5k's should be fine), and a single resistor on the cathode but that should only cause uneven display brightness.

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Sounds like pins 14 and 15 or 13 are shorted. Check your circuit, pull out the chip and measure resistance between them. That would explain half Vcc when g is high and other pin low.

Also, in your original post you stated first that F is 1.8V but than later that it is 3.6V. So, which segments are missing when you display 4 and 6?

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