"I think what Erik is saying is that whether you require external pullups with an 8051 will depend on the variant & pin chosen?

I was planning on using my AT89C52 port 3, which doesn't require pull ups to drive LED's, so I assumed that it would not need it for this. It did of course fail, and as these things go, I decided to make circuit boards instead of fiddling around with breadboards all the time. so I kind of got distracted.

I do intend to go back to this project very soon, so It would be nice to know for then :-)

Chris.