FlowolF
Member
Hi folks - Anyone here got one of the above lathes/motors?My Unimat SL here has a sick motor I've been trying to repair/diagnose.
It's the UG-7750 motor.
Problem is it started running loud/rough/slow/rattly sounding, and when I opened it up I noticed arcing between a couple or so of the commutator copper contacts.
I dressed the brushes, cleaned up the contacts, and still the same.
Got someone to re-true/skim the commutator on a lathe, still same problem.
The suppression caps are checked (fine), everything was thoroughly wire brushed, toothbrushed and alcohol cleaned after each procedure so it isn't conductive debris.
Checked for worn bushings/bearings (they're fine).
Resistances between rotor windings seem consistent but I don't have the values they are supposed to be - anyone here help me out with those figures?
The other thing I don't know is if the commutators on these motors are supposed to have an undercut (gaps cut into the insulator between the contacts) or if they are supposed to be machined flush - I do know some motors need undercut, some need to not have undercut - anyone here in the know who'd care to enlighten me on this?
Other things I checked - bypassed the motor switch as I hear these can deteriorate inside start going intermittent with the motor vibrations causing similar symptoms - still same issue; also checked all other wiring joints etc.
If any of you kind folks can think of anything I may have missed please help! - The lathe she doesn't run well from a little cheap converted 70w sewing machine motor and I have stuff to do, dagnamitt.
Thanks again,
Shaun.
It's the UG-7750 motor.
Problem is it started running loud/rough/slow/rattly sounding, and when I opened it up I noticed arcing between a couple or so of the commutator copper contacts.
I dressed the brushes, cleaned up the contacts, and still the same.
Got someone to re-true/skim the commutator on a lathe, still same problem.
The suppression caps are checked (fine), everything was thoroughly wire brushed, toothbrushed and alcohol cleaned after each procedure so it isn't conductive debris.
Checked for worn bushings/bearings (they're fine).
Resistances between rotor windings seem consistent but I don't have the values they are supposed to be - anyone here help me out with those figures?
The other thing I don't know is if the commutators on these motors are supposed to have an undercut (gaps cut into the insulator between the contacts) or if they are supposed to be machined flush - I do know some motors need undercut, some need to not have undercut - anyone here in the know who'd care to enlighten me on this?
Other things I checked - bypassed the motor switch as I hear these can deteriorate inside start going intermittent with the motor vibrations causing similar symptoms - still same issue; also checked all other wiring joints etc.
If any of you kind folks can think of anything I may have missed please help! - The lathe she doesn't run well from a little cheap converted 70w sewing machine motor and I have stuff to do, dagnamitt.
Thanks again,
Shaun.
