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How to wire if forgotten, Myford help me.

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Gary Lewis 203/08/2019 13:10:58
10 forum posts
9 photos

I've been left a Super seven to replace my ML. However I don't know how to wire the motor. Ten years ago when we moved it we forgot the wiring, someone wired it to a UK plug and it works. Now it's in my possession I would to to get it up and running correctly. I've added pictures of motor, lead and control panel.




Howard Lewis03/08/2019 16:42:30
3128 forum posts
2 photos

Your picture makes it look as if the wires are connected at the motor end, so that what you need to know is where the wires go on the Forward / Reverse switch on the panel.

Although, not being an electrician, it looks as if the wiring between the motor and switch will need to be revised. The Blue / brown /earth leads will probably only allow the motor to run in one direction, having been fitted to confirm that the motor runs.

For Forward / Reverse operation, I would expect the Brown and Blue leads to be connected to the switch, so that it can determine where the current should go, for each direction of rotation.

I would guess that the switch will change over the connections to the start winding?

Don't take my word for it. Ask some one who REALLY knows



Guy Lamb03/08/2019 17:38:51
85 forum posts

Can't be sure but changing round the brown and blue wires won't change the rotation. As single phase motors usually have a running winding and a starting winding (connected together at one end AZ in your photo). The direction in only one of the windings should be reversed to make the motor run in the opposite direction, this is done using a rotary switch.

It's possible you'll need a rotary switch (Myford 7s had a 'D' shaped job) and also be able to identify the separate windings in your motor (starting winding probably has a higher resistance than the running winding). Then it's a case of connecting up the switch, including its internal wiring to the motor windings.

Plenty of wiring diagrams to choose from on the www but if you're not confident ask a competent person to check your work.


Former Member03/08/2019 17:50:48

[This posting has been removed]

Gary Lewis 203/08/2019 17:52:23
10 forum posts
9 photos

I think my motor wiring has been changed to accept a standard three pin plug power supply.

I have since found this, **LINK**

I think I need to make my motor wiring back to standard as per the link/pictures, then I have an electrician friend who can test and wire my original forward/reverse, on/off buttons back up using the green,blue,white and red from my lathe control panel.

I think the original wiring was working ten years ago, it's just that we forgot how to wire it back up. We took the motor to a guy who connected a UK plug and lead directly. It's been like it since.

john fletcher 103/08/2019 20:35:28
580 forum posts

Hello Gary, that is an excellent article which you refer to, I've never seen it before.I hope you now have sufficient information to get your lathe running. Its a good idea to get your electrician friend to check thing out before switching on. John

Gary Lewis 203/08/2019 21:30:10
10 forum posts
9 photos

Yea, I was very lucky to find it just after posting, I don't think that article was around ten years ago???

Guy Lamb04/08/2019 23:26:34
85 forum posts

Let us know how you get on Gary.


Gary Lewis 205/08/2019 07:30:02
10 forum posts
9 photos

I think I need to make my motor back to standard and then check my forward/reverse switch to see if has numbers like below.


SillyOldDuffer05/08/2019 10:00:10
5607 forum posts
1153 photos
Posted by Gary Lewis 2 on 05/08/2019 07:30:02:

I think I need to make my motor back to standard and then check my forward/reverse switch to see if has numbers like below.


The circuit looks right provided the internals of the Dewhurst are wired as described in the Instructable. No reason to doubt that so it should work.

One thing though, my experience of equipment where someone has been 'at it', is that - quite often - modifications were made to bypass a broken component. Dewhurst switches are not wonderful examples of electrical technology and they suffer damage if a previous operator ignored the manual and persistently uses the reversing switch to power the lathe on and off. With the cover off have a good look at the contacts whilst turning the switch; it may need to be replaced. So, don't be disheartened if rewiring doesn't work, it could be a broken switch. Personally I wouldn't replace it with another Dewhurst (only available secondhand), a modern switch is a better bet.

Similarly the Lathe's front panel has Red and Green buttons typical of a No Volt Release switch. These also go dicky with age, perhaps refusing to latch 'ON'.

If more debugging proves necessary, ask again. Bit of a faff but all fixable.


Gary Lewis 205/08/2019 16:29:10
10 forum posts
9 photos

Today I removed my control panel (Which has Myford written all over) to check what's going on in there.

I also plugged it into the mains. When I press the start button there is a big clunk so I guess my No volt is working. It does this in the forward and reverse positions but not whilst off.

ONLY TWO wire are connect to the motor cable, the others are tapped up.




Gary Lewis 211/08/2019 08:34:48
10 forum posts
9 photos

Update to help others, after a lot of research and testing from a friend I can confirm that my motor has only three wires, red, black and yellow. Black and red are for the main running windings and yellow is the start winding.

There are two other wires which for some reason were paired up (brown/pink), these are a thermal cut out which does work so has been back into the circuit.

This type of motor is NOT REVERSIBLE. The only thing I don't understand is why neutral (blue) is wired to my red of the windings, we did try reversing the live and neutral but the motor does not change direction.


Les Jones 111/08/2019 09:16:51
2121 forum posts
146 photos

In the picture in your post of Aug 11 08:34 there also seems to be a light brown wire from inside the motor connected to terminal "T" (Top right terminal.). If that is the case then I think this light brown wire is one end of the start winding and the yellow wire is the other end of the start winding. In your first post it also looks like there is also a thick brown wire going off to the right of terminal "T". Can you confirm if this is the case ? Also is there a start capacitor either on the side of the motor or inside the control box ?


Gary Lewis 211/08/2019 11:35:13
10 forum posts
9 photos

Les, my motor only has three wires to the windings, look here @ 7min 48 seconds. **LINK**

The two other wires which were both connected to "T" were/are a thermal cutout switch, which I have put back into the windings circuit and it works. I don't know why someone disabled it?

Les Jones 111/08/2019 12:56:42
2121 forum posts
146 photos

I had not realised that you had taken the motor apart and found that one end of each of the two windings was jointed where the transition was made between the enamelled wire and the flexible wire. I assume the picture in this mornings post is with the thermal cut out disabled. I have not seen this type of motor with an internal thermal overload. They normally rely on thermal overload current sensors on the main contactor.


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