Most common faults with Logic series machines are blocked pressure bottle, motor brushes and pump failures (sole pumps) or blockages – having no filter. I think EMW may still do the timers and modules for them IIRC.
On very rare occasions the tacho istelf goes O/C it was more common for the magnet to break up or come adrift.
I might even have an old tacho coil lying about if you need it, although they did use a different type on later models I think I even saw one of them in the garage when I was rummaging last year. 😆