Capacitor for 240v 1/4 hp vintage lathe.

[David Aungier]

I believe I need a replacement cap for my lathe, problem is I am not too tech in the electric motor arena so I have a job explaining exactly what I need. I'd be grateful if someone could point me in the right direction if I explain what has happened and what I have gleaned so far. Originally I believe I overloaded the motor a couple of times when the gear train had seized which resulted in the motor only running slowly since. I am not sure if it is 'run' or start and run but when I tested it the needle on the multitester went up and stayed there instead of returning to zero which means that it is faulty but I am not sure if it means that the 'run' part is the fault alone, as I say, I don't know the exact nature of the required capacitor. The motor is made by Brook motors, model Gryphon, single phase , cont rating. Thanks in anticipation David.

 

[kellys_eye]

Does the capacitor have any markings?

If not, a suitable value would be around 4 - 10μF.

 

[David Aungier]

Does the capacitor have any markings?

If not, a suitable value would be around 4 - 10μF.

Hi,
no marks at all, thanks for the ref. Would that be a start run capacitor?, thanks.

 

[kellys_eye]

Do you have any details of the winding connections?

when I tested it the needle on the multitester went up and stayed there

...as it would.

instead of returning to zero

not unless you reverse the connections - and even then it goes back up again!

The capacitor MAY be faulty but you'd need a proper tester to discover the fact.

Does the motor shaft otherwise rotate freely, no binding, no noises?

 

[Minder]

One way to check the cap is to remove any belts etc and give it a fast spin at the same time be careful turn the power on, If the cap is the problem, it normally would run in either direction, which ever way you spin it.
If replaceing the cap, ensure you get motor start/run rated version and NOT Chinese origin.
M.

 

[David Aungier]

The motor rotates freely...I'm afraid I don't know anything about the wiring. Originally, the motor ran at speed in both directions through a reverse switching unit but since the problem it only runs in one direction and at low speed. I am happy to replace the cap to start the process of elimination but obviously need to have the right one

 

[David Aungier]

One way to check the cap is to remove any belts etc and give it a fast spin at the same time be careful turn the power on, If the cap is the problem, it normally would run in either direction, which ever way you spin it.
If replaceing the cap, ensure you get motor start/run rated version and NOT Chinese origin.
M.

Many thanks for that, I'm looking into that

 

[Minder]

You could try the values suggested, if you want to zero in on the correct one, try a value and monitor the current, if close to the motor rated plate current it should be OK, one way is to obtain 3 or 4 of low value and place them in parallel one at a time and test current.
It is not super crytical.
M.

 

[David Aungier]

Thanks again, will try. David

 

[David Aungier]

Many thanks for that, I'm looking into that

I have carried out the test pull starting the shaft with no capacitor connected. the motor runs at what looks like full speed in one direction only. once it is running I can press the stop button and wait till it slows and press start and it fires up again. As I mentioned before, with the cap in place it will start on the button in one direction only and run slowly. I am looking to upload some pics ( including the reversing switch box ) etc which I hope will be helpful. I have an 8uF start run capacitor on order, do you think it will make sense to connect it up and have a go? thanks......The existing cap is there sitting on top of the switch box.

 

[kellys_eye]

Does the label on the motor show "25 MF"???

If so, this is the capacitor value (25μF)

 

[David Aungier]

I'm afraid not, all the data on the plate is mentioned in this thread but no ref to MF or uF.

 

[Bluejets]

Show all the detail you can i.e. The motor terminal connections, where the other end connects in to , the cap connections etc etc

 

[David Aungier]

Ok I've had a good look and taken pics and I will try to describe the set up, which appears to be somewhat 'customized' My sketch shows the terminals behind the inspection plate. Internal motor wires are connected to the terminals as follows.....red wire to terminal A.....a second red wire to terminal B....a black wire also goes to terminal B. The supply cable coming from the switch box has five wires coming from it, Two blacks which feed into the capacitor via the white connectors. A red wire which goes to terminal C......A yellow to terminal A....and blue wire to terminal D. The switch box is supplied by 13a ring main. Please let me know if you require any more info, regards David. I 'renamed' the terminals because I can't see or remember what they are!

 

[kellys_eye]

The terminal plate has labels on it already - I can see 'A₂' on one of them. What are the other designations?

 

[David Aungier]

I have re-labeled the terminals on my sketch....A =Z1....B=A2....C =A1....D =Z2. (Z2 and A2 are linked via a copper strip)

 

[Bluejets]

Something does not appear correct there as there is no need for a start capacitor to go back to the reversing switch.

Four cables yes, but 2 should be the run winding and 2 the start winding with the capacitor wired into the terminal block on the motor.

Someone played with the wiring I suspect.

Link is not normally used when there is a reversing switch, but we can forget about that for the moment.

Method to reverse is to interchange the run winding with respect to the start winding (hence the four cores)and as far as I can see this is not possible with your present setup.

Can you show a pic inside the control box also please.

Really needs an earth to the motor as well, looks like it is rubber mounted.

 

[73's de Edd]

Sir David Aungier . . . . . ( Spelled chek is ????? questioning??????? if you knows how to spels ur last name ? )

With all of your info given and the fact that the motor will run normally, with an assistive hand mechanical start "boost".
(This happens to me occasionally, but its because of sawdust getting into my motor and accumulating between the centrifugal switch contacts.)

With the HUMMMMMMMMM coming from the unit, is pointing to a bad capacitor. And with that unit being a 1964 manufacture, now, after 54 years . . .it's about time.

With you having a 8ufd unit coning , then, how about a full disconnect of the old cap unit at the Euro terminal connectors and hook in the new cap.
Power up and then . . . . . .watch that sucker goooooooooooooo.

73's de Edd
.....

 

[David Aungier]

Something does not appear correct there as there is no need for a start capacitor to go back to the reversing switch.

Four cables yes, but 2 should be the run winding and 2 the start winding with the capacitor wired into the terminal block on the motor.

Someone played with the wiring I suspect.

Link is not normally used when there is a reversing switch, but we can forget about that for the moment.

Method to reverse is to interchange the run winding with respect to the start winding (hence the four cores)and as far as I can see this is not possible with your present setup.

Can you show a pic inside the control box also please.

Really needs an earth to the motor as well, looks like it is rubber mounted.

I'm sure you are right, there has been some 'non regulation' practice brought to bear but I can imagine the previous owner pointing out that it was working ok when he sold it. I have taken pics of the exposed switch box. You will be able to see the outgoing wires connecting to one of the relays. I did clean all the relay contacts obviously with no success. I fitted an 8uF cap today which was partly successful in that, it now runs at full speed in one direction and slowly in reverse. Having said that, I found that if I put the belt on the fast pulley, increasing the starting load, the chuck takes longer to spin up to speed and reverse fails to rotate. I am wondering if I ought to settle for forward only and see if the motor has enough torque to do the job?

 

[David Aungier]

Sir David Aungier . . . . . ( Spelled chek is ????? questioning??????? if you knows how to spels ur last name ? )

With all of your info given and the fact that the motor will run normally, with an assistive hand mechanical start "boost".
(This happens to me occasionally, but its because of sawdust getting into my motor and accumulating between the centrifugal switch contacts.)

With the HUMMMMMMMMM coming from the unit, is pointing to a bad capacitor. And with that unit being a 1964 manufacture, now, after 54 years . . .it's about time.

With you having a 8ufd unit coning , then, how about a full disconnect of the old cap unit at the Euro terminal connectors and hook in the new cap.
Power up and then . . . . . .watch that sucker goooooooooooooo.

73's de Edd
.....

Hi Edd?.......not sure if you think my name is weird, or , you think I haven't got to grips with the spelling of it yet?, anywho, as Frazier would say. Thank you for your directive, I'm guessing that you are able to see all the thread relating to my problem, if so, you will be privy to more info listed in my latest post. Armed with that, I hope you will be able to run the rule over the bigger picture and possibly come up with some more profound observations.Regards Sir David Aunge....Aignr...Unger....Onja!