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Round Dial Electrical Starting Problem

kvom

Plastic
Joined
May 16, 2008
Location
Cumming, GA
About 10 years ago I was active on this forum as people here helped me get my lathe running. It's been problem free as a home shop hobby lathe since then, running on a 7HP rotary phase converter through a 4-conductor plug in the wall next to it. Machine has the original motor generator. It has never run in reverse, but I've never missed that and ignored why.

Today I had the lathe unplugged as I was running another machine tool via the plug. But when I reconnected the lathe it won't start. After pressing the start button, I push the stop button and hear a faint click in the headstock. Then I potentially worsened the problem by undoing the the switch from the rear of the headstock, thinking to see where the click was coming from. When I did so pushed the start button, I got a loud spark and a bit of smoke from the switch (did I ground it by laying it out?).

Adding pics of the switch box and rotary switch. The bottom red wire looks the source of the smoke as the connector is discolored.

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I'm pretty useless in diagnosing electrical issues, so any help is greatly appreciated.
 
I'm pretty useless in diagnosing electrical issues, so any help is greatly appreciated.

This is really basic stuff. I would like to help, but given the evidence of what you've done so far, I think your best strategy would be to ask a friend or an electrician to come look.
 
I'm pretty useless in diagnosing electrical issues, so any help is greatly appreciated.

I would start by replacing the red wire that appears burnt out, to see if that wire went bad on the burnout. It should be 12 or 14 AWG and If I remember correctly, the run isn't that long. You should be able to pull the new wire with the old one. Put ring terminals on both ends and heatshrink
 
I would start by replacing the red wire that appears burnt out, to see if that wire went bad on the burnout. It should be 12 or 14 AWG and If I remember correctly, the run isn't that long. You should be able to pull the new wire with the old one. Put ring terminals on both ends and heatshrink

That sounds within my capability.

In the interim I'm adding pics of the interior in case there's other things I could check right away. I have a Fluke voltage detector that would signal by proximity without me electrocuting myself.

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That sounds within my capability.

In the interim I'm adding pics of the interior in case there's other things I could check right away. I have a Fluke voltage detector that would signal by proximity without me electrocuting myself.

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Here is a question you need to answer first is does the motor generator run? it is in the second picture. The wire you shorted out goes to the spindle motor control box third picture picture it does not look like you burned it out but you need to check it with a ohm meter. That switch does not control the motor generator. The first picture in the first post controls the relay that starts the motor generator start stop buttons that relay is located in a compartment behind the spindle.

Another question do you have a volt meter if not you need to get somebody that knows how to use one?
The voltages you are dealing with are very lethal and any slip ups your spouse will be selling your lathe.
 
220V warning understood.

I have a VOM and have been testing for open/closed connections without any power applied. Here is the scene of my investigations:

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There are two conduits at the bottom of the casting. For one, the 3 black power supply wires come up from the box where the power cord enters. These go to the blocks labeled L1, L2, and L3.

The wires from the switch come through the casting and down. The two red wires on each side of the switch are closed with the switch in center position and open otherwise, which makes sense to prevent starting with the switch in fwd/rev. One of the red wires then goes to a connector on the block, while the other goes down into the other conduit, along with all the other wires. I trace the conduit to a junction block that has two other conduits that appear to go the tailstock side, but it also seems that there must be an opening to the cavity in which the start/stop buttons live.

In fact, the red wire in question leads to the start switch (0 ohms between the supposed ends). That's fortunate as replacing the entire wire via its conduit runs would be very difficult.

The fwd/reverse switch gangs together a pair of the black wires that all go into the conduit. I presume this is how two of the phase are switched to reverse an AC motor. But since the motor generator doesn't start fwd/rev seems irrelevant to the current issue.

Question: does reversing the AC motor and generator also cause the DC motor to reverse?
 
I think I may have identified the problem. The start button has two red wires connected and circuit is open. Pushing the button in doesn't appear to close the circuit, which makes me think the switch has gone bad. I have been noticing of late that it seemed I need to push the button a bit firmer/deeper than before.

Obviously a way to test this is to short out the two switch terminals momentarily if there is a safe way to do so.

Other question is where the other wire attached to the switch leads? Assumption is that it is the other red wire on the starter block.

*** Edit ***

Got wife to hold VOM connector on the start block terminal and verified that the other wire from the start button goes there. I removed the button from the panel in order to verify test more easily, and in fact pushing the button doesn't close the circuit. However, the button is a 2-pole switch and the other pole does close, so my plan is to move the wire pair to that pole and hopefully all will be well.

*** Edit 2 ***

Hope didn't come through. Still no start. I hear a "snap" when I hit the start, and another click when the power is removed. :bawling:
 
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Next step is to make sure you have all 3 phases from the RPC.
120 V to ground for the power company phases and 200 +/- on the manufactured phase.
Then roughly 200 - 240 Volts phase to phase.

There is an arrow on the MG set that must be observed.
The spindle motor is reversed by the DC panel by the spindle motor.

Bill
 
Since my 3PH grinder works on the same outlet, I assume that's not the issue. So I assume I'd measure between the L1/L2/L3 connectors at the top of the motor starter. Correct?
 
Easier than it was 75 years ago. Grab some high-tech and brute-strong Kevlar weed-wacker / string trimmer line and fish it - if you cannot trust the simpler Old Skewl trick of using the OLD wire to pull a NEW wire each of several, one at a time. Which also insures you are DOING the specific wire out of several that you WANT to do!

Tedious, but dirt-simple and goof-proof, actually.

What's the best way to attach the wire to the string? The conduit is stuffed pretty well with wires.
 
I think I may have identified the problem. The start button has two red wires connected and circuit is open. Pushing the button in doesn't appear to close the circuit, which makes me think the switch has gone bad. I have been noticing of late that it seemed I need to push the button a bit firmer/deeper than before.

I just ordered this from Parts Super Center to have a spare, which carries most of all the old GE parts
The current model to replace the existing switch is

GED CR104PBL11G11L6

It is 105 plus tax and is the whole assembly, the switch and the green cover

Parts Super Center | GE Renewal Parts Provider
 
I spent a good while this afternoon with the VOM, and have a better idea of how it's supposed to operate.

First I measured from the plug end to the L1/L2/L3 terminations, and got good 0 ohms for each between one contact and one terminations. The ground blade was 0 ohms to the ways.

There are 3 red wires in the on/off switch cavity. The one in the center between the two switches connects to the L1 termination, hence powers both switches. It connects to the ON switch and is jumpered to the OFF switch.

The other side of the ON switch goes to the rotary switch. The other side of the OFF switch goes to the terminal of the starter with the blue wrap on the left side. Its partner connector below is connected to L3.
The other side of the rotary switch goes to the blue wrap connector on the right side. This connector in turn is jumpered to its partner above.

The OFF switch is normally closed, so before startup three of the 4 starter connectors have voltage applied. When the rotary switch is in the spindle stop position and the ON button (normally open) is pressed, the starter has all for connectors powered. Presumably the solenoid inside then closes the circuit that starts the motor, and that when the ON button is released, the power at the other 3 are sufficient to keep it closed.

Then when the OFF switch is pressed, power to two of the three contacts is removed, which therefore should open the motor circuit. I'd note that this has never worked since I've owned the lathe, and to stop the motor I turn off the phase converter. A click when pressing the OFF button would never be heard with the motor running.

After writing the above, I went back to the shop as I had remembered something I was told here a decade ago, that there are protective "fuses" on each of the power lines that will melt if voltage is too high and protect the downstream components. So I measured resistance across all 3 of these fuses and found only T2 was a closed circuit. I decided to remove the one on T3, and it basically disintegrated in the process. It's clear from the melted wire that it did its job.

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The fuses on the lathe are marked N21 on the plastic exterior. A decade ago, on advice here, I found some Allen Bradleys that are N33 and N36. Since the lathe was running fine, I never replaced the N21s. But I guess that day has come. The N33 is much simpler than the N21:

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The fusible element is just a strip of some metal.

What sayeth the experts here? Replace the two burned out ones with these? Replace all 3? What size is original on the lathe and are they still available?

Mounting on the starter just places the fuse inline with the power.

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Since you seem to want to buy parts, lets make sure you buy the correct ones first.

I went to the website, but the search feature doesn't recognize this part# :confused:

That is because your switch has been replaced with a Cutler Hammer.
Here is one on ebay :Eaton Cutler Hammer Contact Block 2 NO 10250T2 | eBay

"Since my 3PH grinder works on the same outlet, I assume that's not the issue." You have verified that you have power at the outlet only.

"So I assume I'd measure between the L1/L2/L3 connectors at the top of the motor starter. Correct?" Yes, post your readings for the 6 voltages here.
Once you have proper power to the motor starter, then we will figure out what else is damaged, wires burned open or contacts welded shut.

Bill

You were posting while I was.

Here we are 20 posts into your problem and we still don't know what your voltages are.
Where is the manufactured phase? this is very important!


Before you start messing around and buying overload heaters that may or may not be appropriate, we need the nameplate data from the nameplate on the AC motor of the MG. Amps and SF (service factor) need to be known.
 
They are called heaters and are sized according to motor amps draw and It is your problem with two failed the motor will not run and with the one good phase that you have was able to power the control side of the lathe. put some new heaters and give it a try. It sounds like you have a grasp of how the relay works. It also after looking at the pictures that you had loose connections and that is what burned the heaters.
 
I spent a good while this afternoon with the VOM, and have a better idea of how it's supposed to operate.

First I measured from the plug end to the L1/L2/L3 terminations, and got good 0 ohms for each between one contact and one terminations. The ground blade was 0 ohms to the ways.

There are 3 red wires in the on/off switch cavity. The one in the center between the two switches connects to the L1 termination, hence powers both switches. It connects to the ON switch and is jumpered to the OFF switch.

The other side of the ON switch goes to the rotary switch. The other side of the OFF switch goes to the terminal of the starter with the blue wrap on the left side. Its partner connector below is connected to L3.
The other side of the rotary switch goes to the blue wrap connector on the right side. This connector in turn is jumpered to its partner above.

The OFF switch is normally closed, so before startup three of the 4 starter connectors have voltage applied. When the rotary switch is in the spindle stop position and the ON button (normally open) is pressed, the starter has all for connectors powered. Presumably the solenoid inside then closes the circuit that starts the motor, and that when the ON button is released, the power at the other 3 are sufficient to keep it closed.

Then when the OFF switch is pressed, power to two of the three contacts is removed, which therefore should open the motor circuit. I'd note that this has never worked since I've owned the lathe, and to stop the motor I turn off the phase converter. A click when pressing the OFF button would never be heard with the motor running.

After writing the above, I went back to the shop as I had remembered something I was told here a decade ago, that there are protective "fuses" on each of the power lines that will melt if voltage is too high and protect the downstream components. So I measured resistance across all 3 of these fuses and found only T2 was a closed circuit. I decided to remove the one on T3, and it basically disintegrated in the process. It's clear from the melted wire that it did its job.

large.jog


The fuses on the lathe are marked N21 on the plastic exterior. A decade ago, on advice here, I found some Allen Bradleys that are N33 and N36. Since the lathe was running fine, I never replaced the N21s. But I guess that day has come. The N33 is much simpler than the N21:

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The fusible element is just a strip of some metal.

What sayeth the experts here? Replace the two burned out ones with these? Replace all 3? What size is original on the lathe and are they still available?

Mounting on the starter just places the fuse inline with the power.

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Just WOW, there is so much muddled thinking in this post I don't know where to start.
Coupled with things are not connected properly along with self inflicted problems along the way.

N21's are heaters rated for 3.7 amps. N33's are rated at 11.8 amps and the N36 at 15.7amps.

Really a mystery here:
"The OFF switch is normally closed, so before startup three of the 4 starter connectors have voltage applied. When the rotary switch is in the spindle stop position and the ON button (normally open) is pressed, the starter has all for connectors powered. Presumably the solenoid inside then closes the circuit that starts the motor, and that when the ON button is released, the power at the other 3 are sufficient to keep it closed."


So you have a bad stop button contact, or the operator assembly is not working properly or another short is across the stop button contact:
"Then when the OFF switch is pressed, power to two of the three contacts is removed, which therefore should open the motor circuit. I'd note that this has never worked since I've owned the lathe, and to stop the motor I turn off the phase converter. A click when pressing the OFF button would never be heard with the motor running."
So to troubleshoot,
1, Unhook the wire on the stop button that does not go to the start button.
2, Look for a 0 ohm connection across the stop button.
3, Then push the stop button, does the 0 ohm go open circuit?
4, If yes for both checks, the stop button is probably OK.
5, Check for 0 ohms between the wire disconnected in step 1 and the wire still connected to the stop button.
6, If not 0 ohm, tell us what you have.

Lets work on 1 problem at a time and don't try to explain how you think it works to a guy that has done this kind of work for over 50 years.
Provide answers to my questions as best you can and I will direct your efforts.

Post pictures of the "bad" N21's and also a picture of where they came off.
Long with the full load amps on the AC motor nameplate and any AF or service factor ratings.

Bill
 
Quick response to the previous.

1) Until this week I didn't realize that the pushbutton and contact block were separate parts. Since one4 half of the contact block works I don't need a new one currently.

2) For whatever reason my Monarch book doesn't include a schematic. I'm not sure looking at it would be as helpful to me as tracing the wires was.

3) I'll try to locate the data plate on the motor. My lathe is positioned with the tailstock end close to the wall, so find it might be a problem. If it can be seen from the other doors that would be easier than moving it.

4) I'll also try to measure the phase voltages. Presumably it's safe to use the AC voltage setting on the VOM, but I'll try to do so without touching any part of it.
 
I tested the stop button across the terminals with the wire connected and it was as it should be. I'll disconnect the wire and retest if necessary. Pictures of heater and its prior home are posted.
 
I tested the stop button across the terminals with the wire connected and it was as it should be. I'll disconnect the wire and retest if necessary. Pictures of heater and its prior home are posted.

Remove the other heaters and post pictures of them and where they came from, you said you had 2 that were open.
You are missing solder pot on the picture you did post. I want you to leave the heaters out until we get the start/stop circuit working properly.
The contacts on the thermal overload relays are not hooked up, along with missing parts, when the start/stop is working properly, I will have you replace the heaters with 14 GA jumper wire, and completely bypassing the right unit entirely since there is heat damage from poor connections.

Checked with the moderator Cal.
13.7A for round dial and 14A for square dial.


When you checked the stop button, did it go open circuit when you pushed it??? You have said that it has never worked to stop the MG.

A Monarch schematic at this point will not help you, the parts (motor starter and start&stop buttons) are not OEM and the circuitry is not wired properly. The AB starter you have in the lathe is one of the best ever made, We just need to move step by step until all issues are resolved.

I will check back in the AM.
Bill
 








 
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