Author Topic: NVR switch not working  (Read 251 times)

Offline NormanV

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NVR switch not working
« on: May 07, 2018, 09:00:05 AM »
Can somebody help me please.
The NVR switch on my lathe has stopped working. It is forty years since I had a look inside one of these and I have forgotten everything I knew (it wasn't much!).
If I press the plastic bit by the yellow label on the front the motor runs as normal but stops when I release it. When I press the start button nothing happens.
Thanks in advance.

Offline John Rudd

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Re: NVR switch not working
« Reply #1 on: May 07, 2018, 09:03:39 AM »
Norman,
I suspect the coil that holds it all together is open circuit.....
You will probabky need to replace the nvr unit......
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Offline NormanV

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Re: NVR switch not working
« Reply #2 on: May 07, 2018, 09:08:45 AM »
Which part is the NVR unit?
That was quick!

Offline John Swift

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Re: NVR switch not working
« Reply #3 on: May 07, 2018, 09:10:35 AM »
does this diagram help

when you push the green N/O button
the mains supply will energise the contactors coil
providing both the red stop switch and motor overload switch is closed

this will close a N/O contact wired in parallel with the start switch to maintain the coils supply until you push the stop button

john

Offline NormanV

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Re: NVR switch not working
« Reply #4 on: May 07, 2018, 09:15:40 AM »
My question was a bit more basic. Is the nvr bit the lower of the two parts in the switch?

Offline John Swift

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Re: NVR switch not working
« Reply #5 on: May 07, 2018, 09:30:43 AM »
Hi Norman

with the diagram as reference

you need to check you have  continuity though each normally closed switch   and
the coil (they can fail open circuit)

if the Normally open holding contact on the contactor was faulty then the N/O start switch , which is wired in parallel , would energise the coil as long as it's pushed

like wise
if the start switch was faulty
when you manually push the contactor closed the motor will run and the holding contact hold the coil in

   John




 

Offline John Rudd

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Re: NVR switch not working
« Reply #6 on: May 07, 2018, 09:32:52 AM »
Norman,
Its difficult to see....but I suspect the top part is the nvr relay, the part below it looks like its a thermal overload...
I googled  the model number and nothing comes up.....
Might be worth contacting MTE to see if they do spares...

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Offline NormanV

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Re: NVR switch not working
« Reply #7 on: May 07, 2018, 09:45:27 AM »
Thank you both for your help, I'll have to check it through carefully.
It is so frustrating not knowing how to do it. Fortunately it doesn't happen often enough to be a big problem but it has put an end to today's work.
Thank you.

Offline ZebraDriver

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Re: NVR switch not working
« Reply #8 on: May 07, 2018, 10:18:42 AM »
The upper part is a contactor, the lower part is an overload relay.  If you can press the plastic part labelled 33/34 and the motor runs then that means the coil is ok and it also means that the stop/e stop/overload contacts (95and 96) etc. are all ok. N.B. PRESS THE PLASTIC PART WITH AN INSULATED SCREWDRIVER AS YOUR FINGERS WILL BE CLOSE TO THE LIVE PARTS.  Assuming that this is ok but it does not latch (the motor stops when you release it) then the latch contact is faulty.  The latch contacts are 33/34 and are the ones that the plastic switch is connected to (the switch contacts on the main body, below the opaque plastic are 33/34).
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Offline NormanV

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Re: NVR switch not working
« Reply #9 on: May 07, 2018, 10:45:31 AM »
Ah, that makes sense. the switch contacts 33/34 did give a flash on my first effort with the outer cover off. I think that it may be the switch.
Thanks.

Offline hermetic

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Re: NVR switch not working
« Reply #10 on: May 07, 2018, 02:39:27 PM »
All the above is pretty much on the money Norman, top part is the relay, bottom part is the overloads, just check that if you have aany safety switches on chuck guards, or belt covers, and one of these is open circuit, or the door is open, the NVR will not pull in. Always check the simple stuff first!

Offline NormanV

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Re: NVR switch not working
« Reply #11 on: May 07, 2018, 02:45:30 PM »
Thanks for the suggestions, my lathe has none of those. It is very basic.

Offline vintageandclassicrepairs

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Re: NVR switch not working
« Reply #12 on: May 07, 2018, 04:52:55 PM »
Hi All,
Those thermal overloads do not break the main currents only the control
So the motor will run when the contactor is pressed in
Try pressing in the square red button on the overload, this resets the overload (listen carefully for a little click)

John