Tacho Problem

["Paul Tring" <paultring@blueyonder.co.uk>]

My Series 5 tacho is very erratic with an aftermarket electronic ignition
fitted.I was going to convert it to capacitance coupling (good article on STOA
website) but my tacho is fitted with the later internal loop/single transistor
circuit as fitted to some MG's and bears no resemblance to the Alpine
unit.Does anyone have a schematic or any ideas before I revert back to
points/condensor?
Paul