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planeman
12-29-2013, 11:32 AM
A few days ago I was trying to mill a small slot into some wood with a 2-flute mill using the milling head on my Maximat 7 (http://www.lathes.co.uk/emco/page4.html) and the mill jammed in the wood. The mill motor stopped immediately. No smoke and no burning electrical smell thank God! After clearing the jam and backing out I tried to start the motor and it did start, but it ran very slowly and it did have trouble starting. The motor is 110V and there is no capacitor on the motor itself (the motor appears to be one specially made for the machine). I looked into the back side of the lathe headstock where all of the electricals are located and I see two huge capacitors. One is for the lathe motor I suppose and one is for the mill motor (I am surmising this, I don't know for sure. But it seems logical). My questions are these: 1. Does it appear to those of you who are knowledgeable about electric motors that a blown capacitor is the problem? 2. If so, how do I test the capacitors? I do have some electrical test equipment, but I am not very knowledgeable on these things. 3. Are there any other things I should consider? Thanks for any suggestions!!! Planeman

GNM109
12-29-2013, 12:11 PM
A few days ago I was trying to mill a small slot into some wood with a 2-flute mill using the milling head on my Maximat 7 (http://www.lathes.co.uk/emco/page4.html) and the mill jammed in the wood. The mill motor stopped immediately. No smoke and no burning electrical smell thank God! After clearing the jam and backing out I tried to start the motor and it did start, but it ran very slowly and it did have trouble starting. The motor is 110V and there is no capacitor on the motor itself (the motor appears to be one specially made for the machine). I looked into the back side of the lathe headstock where all of the electricals are located and I see two huge capacitors. One is for the lathe motor I suppose and one is for the mill motor (I am surmising this, I don't know for sure. But it seems logical). My questions are these: 1. Does it appear to those of you who are knowledgeable about electric motors that a blown capacitor is the problem? 2. If so, how do I test the capacitors? I do have some electrical test equipment, but I am not very knowledgeable on these things. 3. Are there any other things I should consider? Thanks for any suggestions!!! Planeman

It is possible that you have a bad capacitor. If you can remove the capacitors from the circuit, you can use an analog multimeter to tell whether the capacitor is open, shorted and whether it still has capacitance. This test will not give you the value in mfd's but will tell you whether the capacitor is still good. Be careful to discharge the capacitors with a piece of metal across the pins before testing them.

Pick a range, something like 10K ohm resistance to start. Connect both leads to the capacitor. The needle should rise momentarily and then slowly drop back to zero. This will tell you whether the capacitor is still working. If there is no movement on the capacitor, you probably need a new one. Hopefully the value will be printed on the capacitor.

For exact values, you would need a direct reading capacitor tester. I have one that only reads to 40 mf. If I want to do a test for actual value and the capacitor is larger than 40 mf, I connect it in series with a known good capacitor with a known value and do the calculation.

"Series capacitor test".

http://www.engineeringtoolbox.com/capacitors-parallel-series-d_1388.html

lakeside53
12-29-2013, 12:38 PM
Before you try to test the capacitor with multimeter, short it out - just in case it is working and has a charge.

The Maximat mill motor is very simple - it's capacitor start/run with no start contacts; the capacitor is powered at all times. There is no thermal overload or other limiting device. If you are looking up electrical data, make sure you are looking at the 60hz single phase model. The 50hz model has a three phase motor with a capacitor across two of the legs for single phase operation.

The first thing I'd check is the disastrous power switch array - very prone to failure.

planeman
12-29-2013, 01:59 PM
I hadn't thought about the switch. I have had this lathe/mill since I bought it new in 1969 and have never had a problem with the switches. But I'll put this in the "things to check" list. And it appears so far that the capacitor is the likely culprit. Thanks for reminding me to discharge that capacitor! That thing is large enough to knock me on my old, aged, and considerable-size a**!!! I'll wait to see if any more nice folks weigh in with a thought. Thanks Guys!!! Planeman

PStechPaul
12-29-2013, 04:50 PM
Given the apparent cause of the malfunction, I think it is unlikely to be the capacitors. The sudden current surge caused by the jam may have caused a winding to open, which should be easy to determine with an ohmmeter.

It is possible to determine the capacitance value using the RC time constant. You could charge it to 9V using a battery, and then use a 1 Meg resistor to discharge it to 3 volts, while using a stopwatch for time. Since T=RC, C=T/R, and using the resistor value in Megohms, the capacitance value should be in microfarads based on the number of seconds. The DMM probably has a 10 Meg input resistance, so that will affect the reading by about 10%, which is close enough. The actual end voltage is 36.8% of 9 volts, or 3.3 volts, but the additional load of the DMM makes the 3V value even closer, and it's easier to remember 1/3 of the starting value.

I just tried this with a 20 uF capacitor, a battery that was only 8.5V, and a 950k resistor, and my stopwatch read 19.26 seconds. Pretty good for a McGyver kluge! :)

gzig5
12-30-2013, 02:28 PM
That's the same mill head as I had on my FB2 milling machine. I would be looking for a fuse but don't remember if there was one on mine, or thermal reset button like you see on some tools. Could be the motor but start with the easy stuff. Did it trip the breaker in the panel? Verify the power all the way into the motor.

lakeside53
12-30-2013, 03:41 PM
Close... IIRC the FB-2 has the very desirable 6 speed oil filled mill head; the Maximat 7 has the 4 speed grease packed head - they are quite different.

co_farmer
12-31-2013, 03:17 PM
Does the motor turn easily by hand? I have a Maximat 7 at home and will check the manual and wiring diagram this evening. I think the two capacitors are for the two speed lathe motor.

Paul

lakeside53
12-31-2013, 04:29 PM
The two capacitors are one each for the lathe and the mill motors. The two speed lathe motor only uses the larger of the two.

planeman
01-01-2014, 12:26 PM
Does the motor turn easily by hand? I have a Maximat 7 at home and will check the manual and wiring diagram this evening. I think the two capacitors are for the two speed lathe motor. Paul Yes, the motor turns easily. And thanks everybody for the help! This is my favorite shop machine. Its my baby! I've got get it fixed. It is still clean as a whistle and like new condition, even though I bought it in 1969 (my God! That's 45 years ago!). I take care of my tools. Planeman

co_farmer
01-01-2014, 08:04 PM
Yes, the motor turns easily. And thanks everybody for the help! This is my favorite shop machine. Its my baby! I've got get it fixed. It is still clean as a whistle and like new condition, even though I bought it in 1969 (my God! That's 45 years ago!). I take care of my tools. Planeman

Ok, now, have you ever had the covers off the gear box? One on each side. There are two sliding gears that are moved by the two levers in front of the box. One or both levers have broken or slipped out of the groove in the gear. Your slow speed and lack of power are because gears are not meshed properly, and just riding on each other. The grease is transferring a bit of power. like a torque converter.

Do not try to force the gears using the front levers. You will need to get into the greasy insides to see just what went wrong.

Good luck, Paul

planeman
01-02-2014, 12:22 PM
Ok, now, have you ever had the covers off the gear box? One on each side. There are two sliding gears that are moved by the two levers in front of the box. One or both levers have broken or slipped out of the groove in the gear. Your slow speed and lack of power are because gears are not meshed properly, and just riding on each other. The grease is transferring a bit of power. like a torque converter. Do not try to force the gears using the front levers. You will need to get into the greasy insides to see just what went wrong. Good luck, Paul Yes, I've taken the covers off the side of the mill head, just to look inside though. and that was many years ago. I'll take a look. Thanks!

mensa.guy
03-18-2015, 10:41 PM
I acquired a vertical extension (milling head & column) for a Maximat v10 (in an attempt to make a milling machine), and it has an inline (single-pole) switch, a capacitor, plug & motor. Motor worked fine, although wiring looked like sh*t, covered in electrical tape, etc. I moved it into my shop and broke it down to clean it. Motor does NOT have access panel on back with six screw/terminals, just wires right into bottom of motor through hole. Motor is 110v, single phase, with brown, blue, black & green/yellow wires.

When I tried the motor again: nothing! The green/yellow wire had disconnected, and there are green (ground) and white (neutral?) wires with connector tabs connected to the (single-pole) switch. I've ran motors that didn't have ground wires, so I figured the ground was going to be disconnected (Argh!) I plugged the green/yellow to the white, plugged in the plug and BAM! Large spark & breaker thrown. I find out (later) that the green/yellow is the ground, but that leaves the white unconnected(?).

Did I just blow the capacitor? Do I need a new one? I've got a (basic) multi-meter, haven't learned to use it, yet.

All I've figured out (way too late) is green/yellow is ground, and (motor) black connects to (capacitor) black. Otherwise, I don't understand what the other colors are. The wiring diagrams for the Maximat connect to relays (which use the brown, blue & black wires); don't have one, don't want one, just want to get a double-pole switch and get this working.

(a little while later...)

I found a post on the yahoo group page, from Gerald Feldman, about wiring colors, only he talks about 240v wiring (I've got a 110v motor).
Created graphic in Sketchup, can't figure how to insert into message...
(Web site "eats up" spaces, so had to use periods for spacing...)


. . . . . . . . . . . Motor
. . . . . . . . . . / | | \
. . . . . . . . . G Bl Br Bk
. . . . . . . . / . / . /\ . . \
. . . . . . . / . / . / . .\ . . \
. . . . . . / . / . / . . . .\ . . \
. . . . . G . W . Bk . . . Br . Bk
. . . . . . \ . | . / . . . . . \ . /
. . . . . . Double . . . . Capacitor
. . . . . . . Pole
. . . . . . Switch

(Actual text)
> There should be four wires coming from the motor: Yellowgreen
> (which is the case ground), Black, Brown, and Blue, and
> you will need a motor-run capacitor of 30 microfarads at 240
> volts (as shown on the motor ratings plate). The Yellow-Green
> wire is the safety ground and goes to the ground wire from the
> AC line supply (Yellow-Green for European or Green for
> USA). The Black wire from the motor goes to one lug on the
> capacitor (this is its only connection). The Brown wire from the
> motor goes to the other lug of the capacitor.
>
> If the wires coming from the motor are not colored as
> described above, there is a way to determine which is which if
> you have an ohm-meter.
>
> The switch should be wired as a double pole, single throw
> switch and is used to turn the motor on and off. (Always wait
> until the motor is completely stopped before changing gears.)
>
> The Blue wire from the motor is the Neutral and should
> connect through the switch to the neutral wire from the line
> cord (Blue for European or White for USA). The Brown wire
> from the motor (previously connected to one side of the
> capacitor) is the Hot and should connect through the switch to
> the Hot wire from the line cord (Brown for European or Black
> for USA).
>
> Hope this helps.
>
> Jerry F.

Is this wiring correct for a 110v, sigle-phase motor?? Can't afford to take it to an electrician. Not sure what to do...

Any help would be greatly appreciated!!

Michael

PS: Sorry for the verbosity...

planeman
03-18-2015, 10:51 PM
As this thread has popped up again I thought I should reply with the following so others might benefit from it. I called DigiKey and asked for a technician. I read of all of the specs on the capacitor for the mill and he fixed me up with an equivalent. I installed it and VOILA! The mil was back running again! One of the easiest fixes I have ever made. Hopefully this will help someone in the future. Planeman

lakeside53
03-18-2015, 11:17 PM
The wiring should be is correct for 120v, but you don't need a double pole switch. Just switch (single pole) the Black mains wire. White (blue) is neutral and can be connected directly. Green (green/ yellow strips) is also connected directly to the frame.

One twist... the European motors were often a three phase. To run on single phase, they connected a capacitor across two legs to introduce a pahse shift for start/run

You need a RUN capacitor, not a START capacitor.