Hi Steve.

Can you please explain why you are abandon this cicuit,
becouse it's just this component I've worked with now for a
several of month.
Parhaps I can help you from my experience of this.The only differens
between my component is, that I'm using the 89LS53 - 3V variant.
I am using the Equinox flash-programmer.
I must say, that it works very properly.

Magnus.