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What is the Box on top of motor

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Adrian Coundley 118/03/2022 15:55:55
5 forum posts
2 photos

Hi I’m looking for some help and information please,I have a single phase motor on my Tom senior mill that has a large box on top of it ,that has 2 wires coming from it to the motor , it’s starting to smoke from the cable and there’s like a electrical smelling oil coming from it I’ve taken the outer cable off to check the inner cable wasn’t arcing but they are ok it seems to be coming from inside the box , I know nothing about electrics and have looked on the net for information about the motor but can’t find anything.I think it might be a start run capacitor and would like to know where I might get a replacement or a modern equivalent.

the motor is a

English electric 1hp single phase motor

frame MC6726

1450 Rpm

250/250 volts

cont rating

condenser 140 Mfd

Sorry I can’t seem to upload any pics thank you for any help

Thor 🇳🇴18/03/2022 16:06:00
1628 forum posts
46 photos

Hi Adrian,

Welcome to the forum. How to post photos here. My guess is you are right it is a capacitor problem, one place to look is here.


Edited By Thor 🇳🇴 on 18/03/2022 16:06:34

Weary18/03/2022 16:32:07
376 forum posts
1 photos

The 'box' fastened to the motor contains a capacitor.

You can replace it with any suitable capacitor. 'Condenser' is a synonym for capacitor, so from the details you have furnished you know that you want a 140 micro-farad, 250 volt capacitor. Usual on-line sources will furnish something suitable. If the 'box' is very small then you may need to look for a physically small capacitor, but the 'box' is normally quite capacious. There will likely be two screws holding the box-top onto the motor, undo those, remove old capacitor, replace with new. Copy wiring and fastening method exactly, as you have observed there are only two wires.

Note that you can run your lather with a failed capacitor, you will have to turn-it-over by hand to start it, then it will run as per normal.



Adrian Coundley 118/03/2022 16:32:10
5 forum posts
2 photos

Hi Thor thank you for your quick reply

Adrian Coundley 118/03/2022 16:34:29
5 forum posts
2 photos

Hi Phil thank you I’ll give it a go

Adrian Coundley 118/03/2022 16:46:06
5 forum posts
2 photos

Hi think I’ve uploaded the pictures now

David-Clark 118/03/2022 17:34:17
220 forum posts

Yes, capacitor, you can use a higher voltage capacitor but not a lower one. Depending on the way it is wired it starts the motor in the correct direction.

SillyOldDuffer18/03/2022 17:42:09
8684 forum posts
1967 photos
Posted by Weary on 18/03/2022 16:32:07:

The 'box' fastened to the motor contains a capacitor.

... Usual on-line sources will furnish something suitable. ...

A high value capacitor like 140µF is almost certainly a Start Capacitor. If the old capacitore is oil filled use rubber gloves, double seal in a bag and dispose carefully - old fashioned oil can go off and emit Dioxines, which are very nasty.

Searching for "Start/Run Capacitor" should find several online suppliers such as Farnell, Mouser, CPC and RS Components. 140µF is an unusually high value, so it may be necessary to make it by paralleling two (such as 60 +80) Or any capacitor ±20% of 140 should work. Only fit a proper Start/Run capacitor, other types are likely to go bang!


noel shelley18/03/2022 17:53:33
1339 forum posts
21 photos

Starting a motor by pulling it over is a HIGHLY dangerous practice, have an ambulance waiting before you do it ! Unless you can get it to about 75% of it's running speed it will NOT run normally and may well be damaged ! The capacitor may well be 400V and will do no harm. The motor is 250v, but see if you can read the voltage on the capacitor. It can be wired either way round but MUST be on the right terminals in the motor. It is a 4 pole motor. Good luck, Noel.

Adrian Coundley 118/03/2022 18:25:47
5 forum posts
2 photos

Hi I’d just like to thank everyone for answering my questions so quickly I’ll have a look at the places people have recommended to me and let you know how I’ve got on thank you all again

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