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Author Topic: 74141 disappointment  (Read 3302 times)
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« on: February 09, 2010, 11:05:14 PM »

Hi guys,

I have built a 4 digit clock using 7441s (because that is all I could find at the time).

To blank the first digit, I simply put it on a separate anode, and disabled it during the multiplexing when the digit was not desired (which used up one extra anode, where I could have theoretically gone with only two).

Finally, I found NOS 74141s at my local electronic surplus store (these guys have been in business for years it seems!).

So I thought I would rewire my clock with only two anodes, and blank the first digit by sending an "illegal" code to the 74141.

Disappointment!  Sad

The "blanked" digit now shows a kind of orange haze when it is supposed to be blank.

Short of reverting to an individual anode for this digit, I was wondering if anybody had met this problem and can come up with a satisfactory solution.

Some details about the construction that I suspect could be of interest:
- The nixies are driven through a 47k resistor with a 10% PWM at somewhat around 50Hz at 200V (which should remind them of their native Russia).
- On this first digit, only the 1 and 2 cathodes are connected, the others are left "floating" (which worked well with the 7441).
- Digit 3 uses the same trick, where cathodes 0 to 5 are connected and the others are also left floating. Except it's never blanked.
- Digits 2, 3 and 4 display the same haze (with all cathodes connected) when provided with an "invalid" code.

Point is: blanking doesn't work...

Any ideas?

Thank you.


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