Quote:
Originally Posted by Silvester
I noticed that you do not use 2K2 pull up resistors on the outputs of the 74LS189, as shown in the original Elektor design. I don't get a ghosting problem on my LEDs using similar circuit to Elektor using 7489 chips with 2K2 pull ups on output. Though I didn't invert inputs and outputs, just buffered outputs with 7417.
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7489 has open collector outputs so it would need pullup resistors. 74LS189 has tristate outputs so shouldn’t need pull up resistors.
The ghosting might be due to modern LEDs being more sensitive to low current or short duration drive currents.