Honey I blew up the mini lathe speed control board

[irving2008]

Hank,

I order a lot from Farnell and need to put an order in this week, so I'll get you a couple - PM me your address and let me know if there's anything else you need. I thought I had one here but I can't find it.

So you have a quad comparater, probably for zero crossing detection, and a pair of quad opamps, probably acting as buffers for RC timing networks to give start up and stop acceleration/deceleration control. I am guessing the transformer is to provide some power to these and a source of isolated AC for the zero crossing detection, wonder how they drive the SCR gates. All the circuitry is operating relative to one side of the motor and floating relative to supply, unless theres a pulse transformer or opto-isolator on there and I dont see it... so be very careful when putting fingers near there...

The picture shows an ouitline of the circuit - there are several ways to do this but it should help sketch out the main arrangement...