MEM Electrics

I have a Boxford AUD with a MEM 85ADS NVR that has refused to engage today but has been working fine for several days.

The solenoid appears to be physically prevented from moving and the contactor parts seem to be very loose.

I noticed that there is a 4BA hole in the bottom of the lower contacts but the is no screw, should there be and is this why the parts seem loose?

Hi Brian,
I have Googled "MEM 85ADS" but could not find any information. I thought it may have been the type that I had works with some time ago. (About 50 years.) Can you post a picture of it ?

Les.

Hello Les and thanks for the reply. Here are two pictures showing the general appearance and the holes including the 4 BA one.

Hi Brian,
It does look similar to the ones I worked on about 50 years ago. I suspect it could be the underside of the moving contact block has broken where it is fixed to the armature of the coil assembly. Possibly a broken bit of plastic is causing the problem. I cant remember how to dismantle them but I think it was faily obvious. I think you will have to remove the base plate to get at the screws that hold it together. Try to avoid dismantling the moving contact block as there are quite a few springs in it. If it broken plastic then you may be able to repair it with araldite.

:Les.

Hi Brian

As Les says that's a quite old starter but they are known to give many years of service.

If you press the red moving contacts bar down you should be able to see the contacts and also the pole faces making contact, if the pole faces don't make contact you will need to investigate further. Start dismantling by removing the 2 screws on the underside of the baseplate, remove these with the assy upside down.

If the pole faces make contact then you have to check the coil and control circuit for the possible fault, if the coil is open circuit I may have a replacement, just need all dimensions to check.

Emgee

I see you have marked some of the wires which is a good idea. So, if you remove the assembly altogether it will enable you to see the problem. I think there should be a screw in where your second picture shows a vacant hole, it together with another one, by your thumb in first picture, holds the assembly down on the grey bottom plate. There is a second retaining bracket at the far(back end ) and if the assembly is not fastened down at both end, It can lift up instead of pulling Red contactor down. Also on the left hand side there are the three over load heaters, there is bar which lifts when an over current takes place, it open circuits the coil control circuit. I've known the bar and its contact to come to be tarnished and not making contact, a slight rub with a piece of steel wool solved that problem. Having looked in my 1964 MEM book It might be of interest to you and other readers these starters were 45 shilling and you could buy spare coil and overload. Hope you are soon on the road once again. John

Many thanks to all for your help. I've dismantled the item as per instructions and find that the main Bakelite body is split in half and has been repaired with some unknown substance in the past.

Is it worth attempting a repair using a modern adhesive or should I be looking for a replacement and, if so are there any recomendations?

Edited By Brian Hutchings on 07/12/2016 16:47:41

Hi Brian,
Only you are in a position to judge if you can glue it back together. You may find it difficult to remove all of the old glue and there could be bits of the plastic missing. You could get a starter such as this one together with a thermal overload from this range of the correct rating for your motor. I THINK it looks like your existing thermal overloads are set at about 5 amps. I can't remember the rating of the motor on your lathe so you will have to check the most appropriate thermal overload to match your motor. You may find a cheaper source. This was jut the first place I thought to look.

Edit. I've just had a look on ebay and found some cheaper. MAKE SURE THAT YOU GET ONE WITH A 240 VOLT COIL. (As they can also be used on three phase many will come with a 400 volt coil which would be connected between phases.

Les.

Edited By Les Jones 1 on 07/12/2016 17:41:23

Many thanks yet again Les, I'm going to get another switch just to be on the safe side. The plate on my motor states 5.5 FLA which I take to mean full load amps?

I had a look on ebay and saw an almost identical switch to mine but it was only for 4.5 amps. but there seems to be lots of others for 240 v, some with a panic button stop, that may be a good idea.

I'll post on here when I'm sorted.

Hi Brian,
It is easy to add an emergency stop button. I have one just below the tray. I can hit this with my leg if required. You are correct FLA is ful load amps. some of the adverts on ebay give the option to select the coil voltage and the range of adjustment of the thermal trip.

Les,

Made my mind up and went for a KEDU KJD18-9 NVR Switch 230V 1ph rated at 12A with additional connections for safety locks on doors (my Boxford has 2 microswitches that switch off power in the event that access doors are open).

Many thanks to all for helpful comments, I don't know what we'd do without you.

While waiting for the new switch to arrive, I decided to make a mounting plate for it. I took the plate containing the rev switch off because I'd forgotten where one of the wires went. Imagine my surprise to find that the mains feed wire had come away from the rev switch! I wonder if that's why the lathe wouldn't start?

I'm not too concerned, having found that the the main body of the MEM NVR had split in half, I'm glad that a new NVR switch is on its way.

Hi Brian

The KJD18-9 NVR does NOT have motor overload protection so cannot be considered a suitable replacement for your broken MEM starter, it is as stated a NVR switch rated to 12A.

Nothing special about having the facility to connect additional devices to stop the motor, that's always available on any starter.

Emgee

Thanks for the reply Emgee, is there anything that can be done to add overload protection (if necessary) to the KJD18-9?

I looked at various offers on ebay and many of the NVR switches stated that no additional devices could be fitted.

I was slightly tempted by an identical MEM unit on ebay but the seller wanted £50 for it and I considered that it must be as old as mine, and in an unknown condition I considered it not worth the risk

Hi Brian

Some overload units are available that are fixed by screws to a backplate independently of the contactor so you could use one of those within the FLC range of your motor to retain the overload facility.

The obvious danger of not using an overload in circuit is burning the motor out, much more costly than providing the proper protection.

The link provided by Les has details of a suitable replacement starter providing NVR and overload protection, you may have to order the overload seperately to the starter assembly. There are many different makes and sizes available.

Emgee

I think the thermal overloads for the hytec starter from Screwfix could be used with the Axminster NVR but you would have to find a suitable case to mount it in, You would have to pass the live and neutral wires that go between the NVR switch and the reversing switch through two of the thermal overloads heating elements and connect the NC contacts on the thermal overload in series with the interlock / emegency stop loop.

Les.

les

A problem I see with the unit selected by Brian is the full load neutral current will be passing through the Stop switch of the unit, as would be the case by the connection through the o/l trip, won't take many start/stop operations to burn either of those pairs of contacts out.

I see on ebay Enclosed starter with o/l for £32 inc pp

**LINK**

Emgee

Toolstation do DOL starters and a selection of overload units to suit.

Mike

Hi Emgee,
Some (but not many.) of the NVR switches have access to one end of the coil so only the coil current needs to flow through the interlocks and emergency stop button. This is one example. (You can see a diagram of the switch in the middle picture of the advert.) I suspect that the unit thet Brian has ordered will use this type of NVR switch. These NVR switches are very crude. The push puttons are not an NC contact for the stop and an NO contact for start. The start button just pushes on the armature of the relay and closed it, The stop button pushes the armature away from the coil. The one in your link looks a much better choice. I also like the fact these proper motor starters have separate maintainer contact to hold the coil in. (Rather than using a contact that also carries the load current.)

Les.

Edited By Les Jones 1 on 08/12/2016 22:06:20

Les, not quite like this drawing then ? from Brians part number.

**LINK**

Emgee