Need a little 'lectronics help

"Snag" wrote in message news:ujgl9o$g51f$ snipped-for-privacy@dont-email.me...

I picked up an overlock sewing machine for a VGP , but I suspect the control is dead . I'll keep looking for a wiring diagram for the motor just to be sure I don't let the magic smoke out while testing it . But the control unit - looking at diodes and power regulators makes me think the output is going to be DC . I'm just not sure of voltage or which terminals do what . I think it's a dual-range speed control from the switch on it . No obviously damaged devices n the control board , I don't see a fuse . I'll be checking diodes and some other components as time permits (winter is coming , right now the priority is firewood) , it might be as simple as a blown diode . I already cleaned the speed control device , next was going to be the power-on micro-switch . If anyone is familiar with Pfaff overlock machines from around 1990 I'd like to pick your brain ... this one is a model 786 Hobbylock machine . The motor and mechanisms in the machine are free and apparently working correctly , no timing issues . Snag

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The manual, no schematic:

Does anything here look like yours?

I picked up an overlock sewing machine for a VGP , but I suspect the control is dead . I'll keep looking for a wiring diagram for the motor

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Does anything here look like yours?

If you don't have an oscilloscope, the DS211 for $20.79 from Amazon is adequate for low speed signals. Since it's battery powered and completely isolated you could look at floating SCR gate drives with it, though I wouldn't touch it with the power on. At that price you could buy two and look at signals referenced to different voltages.

Having several channels helps solve subtle problems, but one may be enough to find where a signal dies in a failed part.

My training in electronics was like 50 years ago ... and while I still understand the basics I'm not up to tracing a signal . I can still test most components but that's about my limit . I'm going to do a little more disassembling to check the condition of the motor . If I can figure out what that problem is and get it to run I will go ahead and get a new pedal control . It's only around 50 bucks for the control , but I've found a couple of problems in the motor unit and I'm not throwing money at this thing unless/until I'm sure I can make it run . My wife has wanted an overlock machine for many years , I'm hoping if I can get this one running it will help motivate her to do more sewing - for fun and maybe a little profit . But mostly to get her out of that damn recliner .

Does the motor have a nameplate that gives its power requirement?

If it does it's on the side I cannot see ... it can't be much of a current load as the input wires are like 30something gauge . A lot finer than I expected . I suspect it's operating voltage range is probably like 24vdc-100vdc or so . I'll be testing with 12 volts from a battery . Might not spin the motor but should let me feel some torque .