Thread: Servo Products Type 90 Specificatios

I've got an old Wells Index 747 with type 90 power feeds. When I got the mill the power feeds didn't work. After replacing some micro switches everything was fine. The other night I noticed the "y" axis feed started tripping the breaker which eventually ended up destroying the breaker. I pulled it apart and replaced the SGRs and now I don't have the tripping condition but I have no movement at all.I've measured voltage at the brush holders and it's reading around 60v regardless of the position of the speed knob. So I have three questions: 1) Does anyone have a schematic for the IC Board? 2) Am I correct in thinking that the drive motor is an A/C reversible induction motor with full wave rectification and 3)What peak voltage should I be detecting at the brush holders. Thanks!

I think that "A/C reversible induction motor with full wave rectification" might more likely be a shunt wound DC motor. In that case, the brushes will have a constant voltage and the field voltage will be varied to vary the speed. Or it could be a series wound DC motor with an SCR control.

Larry

Larry, Thanks for taking the time to post your suggestions. It would make sense that it might be a DC motor as there are a bunch of heavy diodes and two SCRs on the IC board. I was thinking it might be an AC motor do to the way the armature looks. More reading needed on my part.

Wayne, at Bridgeport Knee Mill Parts in stock-Bridgeport and Servo power feed parts and service is a hell of a resource for the old Servo drives. He still the parts I needed to get my 70 series Lagun back in service. Mine ended up being a bad speed control pot. Does yours work if you press the rapid traverse? That pretty much bypasses all the variable speed components.