Hi Pablo,

If you have a look back in one of the earlier posts in this thread (from hughesbros), you'll see the plans for a probe and also the amplifier that goes with it. The probe in those plans normally operates off 12V, which is also too high for a parallel port - that's the purpose of all the circuitry. All I want to do is modify that circuit to run off 35V instead of 12V. Why do something the simple way, when you don't have to...

Regards
Warren