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Discussion Starter · #1 ·
Hi

Sorry, this isn't about routing - but I'm in a jam.:crying:

Due to my total hopelessness concerning all things electrical I'm in a fix over getting my table-saw back into action after a long period of disuse. The saw is a TK 1800 UV Herkules, marketed by a German company but, if not assembled in Asia, consisting I suspect mainly of parts from there (including its NVR switch).

I began testing by simply pressing the 'on' button. It worked - the first time. Having hit the 'off' button I then pressed it again and this time it only ran for so long as I kept it pressed manually: as soon as I took my finger off it the saw-blade ran down and stopped. So thinking I'd better check to see if there might be some obvious way in which I might get it to go i demounted the switch.

I attach pic. The type will doubtless be familiar to anyone knowledgeable. For my part, having tinkered with it a bit and read-up on various websites, I gathered that it's of the magnetic type. It seems that by pressing the 'on' button a contact is mechanically created and the circuit completed while at the same time the magnet by being energised latches it in that state until pressing the 'off' button unlatches it (again mechanically). I hope I've got that right. The mechanical actions seem to function correctly (being so simple there's nothing much that can go wrong) but the switch now fails to work at all so I conclude that a connection to the electro-magnet must be faulty and the switch therefore useless.

Going by appearance alone I ordered what I took to be an exact duplicate of my switch on E-Bay, from Hong Kong. Because I despaired of being able to successfully connect-up a replacement the last thing I wanted was to disconnect the existing switch, but my hope was that if the two were virtual clones I might be able to get round that by cannibalising from the new one (eg by swapping-over their respective front sections). That idea didn't work because they aren't in fact exact clones.

The new one seems (to my untutored eye) to be designed to be used with a three-phase motor (whereas my saw's motor is single-phase) and the connections on the two switches are completely un-alike. The existing switch has what I take to be two duplicate sets of connections on the back side of the switch to which go two pairs of (I presume matching - one pair in and one out) wires with almost completely indeterminate colour-coding which terminate in plastic-sheathed spade-terminals, and two bared earth-leads which go to screws on the saw's chassis (pics attached). The new switch has three matching pairs of connections each numbered from 1 to 3 (one in and one out for each phase perhaps?) and seemingly no ground.

Can these two switches use the same wiring or are they completely incompatible? If they are I shall simply have to send for another one but then I shall still have the problem of telling which wires to connect to which terminals - leaving the earth connections undisturbed meanwhile. Can anyone offer any guidance?

(I do incidentally have a three-phase supply available in my shop but I imagine that that's completely irrelevant in this case).
 

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tried to look your saw up but all of the sites were in Finish(?)...

I believe that you have a tripped overload relay or one leg (a hot) of the switch isn't electrified or you have a blown fuse..

these PDF's have diagrams and troubleshooting guides in them and may be of some help...
 

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Thats european wiring. The brown is Live or HOT. the blue is neutral or GROUND. Green (yellow) and white stripe is earth.
The connections to the switch should be brown and blue in from the mains connected to one side Usually the lower side, and brown and blue to the motor connected to the other side.
The colours must be on the same side of the switch. Do not cross over colours.

If you have connected it correctly, the switch will operate correctly, if you connect it upside down, the switch will only operate the motor while the switch is pushed in.
There are no user repairable parts in there.

Can you show the back of the new switch showing the connections. Its possible we may be able to help to connect it.
 

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We have the same problem in our workshop, exact same switch.
Try pressing the stop button a few times before pressing the start button.
Dunno why but this procedure works for us, hope it works for you.

Good Luck !
 

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Discussion Starter · #7 ·
Thanks guys for coming so swiftly to my aid!

I'll now ponder what you've said (I'm a slow thinker where electrics are concerned - some would say, not only electrics).
@sunnybob
I'll post a pic of the new switch shortly, in case it helps
 

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I agree with Sunnybob. An NVR switch stands for No Voltage Release. The start button energizes the motor And a magnetic latch in the switch mechanism. The magnetic latch keeps the switch closed until you press the stop button which de-energizes the magnetic coil and opens the contacts.

If power is lost the magnetic coil will de-energize, releasing the contacts and preventing the motor from restarting until you press the start button.

This is not a fuse issue. If it was the motor would not start when you pushed the start button.

The only safe thing to do is replace the NVR switch. it does not have any user serviceable parts you can fix.


OldGuy
 
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