single phase motor to NVR switch wiring enquiry

[marbles]

Hi there,

I bought an old Klinger & Born (Elekra Beckum) table saw with what was described as having a faulty on/off switch. Right enough it doesnt start. I hear a mechanical type engagement from the switch and I can see the blade sort of ever so slightly oscillating which was slightly odd but its not rotating.

I thought it might be the switch so bought a (NVR) safety switch and e-stop. I see single phase motor with a capacitor and the cable going to the switch has 5 wires, brown, blue, earth and two black.

I've attached a few pics.

Q: I suppose the first question is what should I look at before assuming the switch is damaged. Does it have a fuse and an internal reset for example?

Q: If I can replace the switch with a more modern NVR which I have, see pic. What is the wiring for the two black wires?

Thanks for any help.

[Clive S]

Does the motor hum if so it could be the capacitor

[Neale]

I'm with Clive - my first port of call would be the starting capacitor. It's not that unusual for one of these to fail and you've pretty much described the symptoms. If you can keep your fingers away from the edge of the blade, it might be possible to spin the blade up by hand with the power on - I used to do this with a disc sander until I found a replacement capacitor. But I have to say it's potentially rather more dangerous with a cutting edge whizzing round so close to your fingers...

Note that the motor will start and continue in whichever direction you spin the blade.

[marbles]

Thanks guys,

Think I might avoid the manual startup haha!

I wondered about the cap as well so I bought a spare of the same value. I see my replacement cap just has four terminals, see pic whereas the original has a length of twin core coming out of the cap, brown and blue. I'm not seeing any marking on the cap hmmm?

[marbles]

Wasnt immediately aware of anythying but wasnt listening out for any humming. I'll try it out to it tomorrow when back in the workshop

[Neale]

Those terminals look like just two terminals with two tags on each. Look carefully at where they are rivetted into the top cap - they are probably a single piece of metal folded.

You didn't mention humming but you did say that it shook a bit - that's why I think the motor is energised but doesn't know which way to go until the capacitor circuitry gives it a kick in the right direction.

[m_c]

That looks like it's a bit more than just a NVR switch. The circuit board looks like it's got some kind of speed controller and/or soft start built in.

It doesn't matter what way the new capacitor is connected as they're not polarised. Just make sure you connect the wires to separate terminals, and not the same pair.