Paul try this web site he talks about a L6203. Are you sure it is a L6503?
There is a schematic to download here.
http://www.pilotltd.net/cnc.htmDerek
There is also a driver chip called a L6503 Have tried searching the net
and Chip Directory et. but no luck so far. Seems a shame to toss it out.
Cheers,
Paul Waller
University of Tasmania
Australia.
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