Arduino unable to bring output level to LOW

Hi everyone,

I'm making a project in which an Arduino is connected to a 3-bit addressable latch, the 74HC259. Between them there is no resistances. There are one transistor for each output pin of the decoder.

The problem is that Arduino seems to fail to bring to LOW the level of the address bus. As a result, the decoder always read the sequence HHH and the same led always turns on.

I measured with a voltmeter the pins and, when the Arduino is connected and the level is LOW, the voltage is about 1.2V. I try to put a pull-down resistance but isn't enough. Address input pins are the only ones that cause this problem.

Some ideas?
Thanks.

You are of course, setting those pins to OUTPUT with pinMode in setup(), aren't you?

Yes, definitions are ok.
And if I test the Arduino outs disconnecting them, the voltage is right.

And if I test the Arduino outs disconnecting them, the voltage is right.

So things are not wired correctly. Please post a schematic of your circuit showing all connections and a photograph of your wiring.

Post your code as well for good measure, use the copy for forum from the edit menu of the IDE.