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10EE starts and stops at low rpm

hawaiianPUNCHY

Plastic
Joined
Oct 16, 2017
Hi,

I have a 10EE square dial MG type, manufactured in 1955.

I've seen similar posts concerning this problem. At rpm below 200 works fine. Once above this rpm the lathe stops and starts until you reduce the setting on the speed control knob. Past solutions were to change the three resistors, which I have done. However, I used a 1kOhm and 2kOhm (in series) on the top and a 2kOhm on the bottom. Original values are 1.6kOhm + 1.6kOhm on top and 2kOhm on bottom. This has not solved the problem.

Should I order resistors to make the 3.2kOhm on the top? I don't know if this will make the difference, or is the problem elsewhere?

Any help would be greatly appreciated.

Thank you,
Dan
 

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Hi,

I have a 10EE square dial MG type, manufactured in 1955.

I've seen similar posts concerning this problem. At rpm below 200 works fine. Once above this rpm the lathe stops and starts until you reduce the setting on the speed control knob. Past solutions were to change the three resistors, which I have done. However, I used a 1kOhm and 2kOhm (in series) on the top and a 2kOhm on the bottom. Original values are 1.6kOhm + 1.6kOhm on top and 2kOhm on bottom. This has not solved the problem.

Should I order resistors to make the 3.2kOhm on the top? I don't know if this will make the difference, or is the problem elsewhere?

Any help would be greatly appreciated.

Thank you,
Dan
That problem is related to the AP (anti-plugging) relay. I explain what's going on it this post: This has nothing to do with the two 1600 Ohm resistors, the A-B resistor pair. Only the 2000 Ohm B-E resistor is involved. I think that you'll find that the AP relay is opening and closing as the machine's speed surges. This is a well know problem with that panel. When you replaced the 2000 Ohm resistor you may not have connected it correctly. Don't assume that it was properly connected when you found it.

Regarding the A-B resistor pair: yes, I would replace them with the correct value, i.e. 3200 Ohms, as discussed in the linked post. There was a reason that the value was used.

Do you have a wiring diagram?

Cal
 
Cal, thanks for the response.

So I guess this is not related to my problem, but I will order the 3kOhm and 200Ohm resistors for the A-B pair. Thank you. Hoping not to digress too much but what does this do?

The AP relay is opening and closing as you have stated. For the B-E resistor, I don't have a wiring diagram and don't know how to check that it is properly wired. I have attached some pictures of my panel. Looks like the 2kOhm is wired between the AP relay and the one to the left of it.
 

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Cal, thanks for the response.

So I guess this is not related to my problem, but I will order the 3kOhm and 200Ohm resistors for the A-B pair. Thank you. Hoping not to digress too much but what does this do?
...
The A-B resistor pair connect to the shunt coil of the FA (Field Acceleration) relay. The FA relay also has a series coil, which is connected in series with the spindle motor's armature. The relay operates when the spindle is accelerating under load and applies full field to the motor, giving it maximum torque, until it reaches speed. We don't actually KNOW what the purpose of the shunt coil is. One theory is that it's there to improve the response time for the relay. My theory is that the FA relay, a Cutler-Hammer #222 relay, is a dual purpose Field Acceleration/Deceleration relay and that when used as an FA relay, a constant voltage is applied shunt coil. There's a discussion here: Field Acceleration Relay See my discussion in post #8.

The AP relay is opening and closing as you have stated. For the B-E resistor, I don't have a wiring diagram and don't know how to check that it is properly wired. I have attached some pictures of my panel. Looks like the 2kOhm is wired between the AP relay and the one to the left of it.
276097d1579639098-10ee-starts-stops-low-rpm-10ee2kohm.jpg
If your 2000 Ohm "B-E" resistor is, in fact, wired between those two terminals, then that's a problem. Here's a photo of the back of the DC control panel from EE38128 which I've annotated with some of the terminal numbers:
EE38128 IMG10662 DC Panel rear, anno.jpg

The terminal immediately below E should be in electrical contact with E. (The two wires on that terminal run to the forward and reverse contactor coils.)

Put a piece of thin plastic strip or card stock between the contact on the AP relay and check the following:
  • resistance from E to C1
  • resistance from E to C2
  • resistance from E to B
  • resistance from B to A
I note that on your panel, the wire from the resistors to the FA relay, which should go to terminal A, goes to the other terminal for the FA relay's shunt coil. This could keep the FA relay from working correctly (unless the polarity of the spindle motor's armature were also reversed). Your wiring looks vintage. Does it appear that the wires to the resistors have been modified?

Do you have a photo of the original resistors before you replaced them? Have you checked the resistance of the original 2000 Ohm resistor? Was the machine working properly for you at some point?

Send me an e-mail and I'll send you my color-coded version of the wiring diagram.

Cal
 
I will check the resistances as you have requested tomorrow evening. Quick answers to your other questions:

The wires do not appear to have been modified, however I may not have an eye to detect this. I may have connected the resistors incorrectly since I did that in a bit of a rush and didn't document the original wiring before disassembling, but I didn't touch anything on the rear of the panel. I have discarded the original resistors but they were all measuring in the ~300000Ohm range. They undoubtedly needed to be replaced. The machine was working fine several months ago. I noticed this problem on my last job which I was forced to complete below 200RPM. I hope this didn't damage anything considering the bad resistors. The only problem I've had with the machine is intermittent dynamic braking, however this is because it is prone to pop out of gear when I turn off the spindle and I always thought it was an issue with the mechanical detent in the back gear/open belt lever.
 
My concern was that someone had hacked it up and left it in a non-functioning state, but since it was running for you, that's not the case. For now, we'll assume that the FA relay's shunt coil is correctly connected. (Your wire A from the resistor is on the opposite terminal from what I normally see, but as long as the FA relay's coils are correctly polarized, that's fine.) By the way, it's the resistance from your terminal A that I need from the list above.

You also need to determine what terminals on the back of the panel connect to the A, B and E terminals on your resistors.

Cal
 
Here's the resistances. Corresponding pictures attached.
resistance from E to C1: 949Ohm
resistance from E to C2: 942Ohm
resistance from E to B: 2.488kOhm
resistance from B to A: 462Ohm

A terminal (my A terminal) goes to 2k and 1K+3K
B terminal goes to 1k+3k
E terminal goes to 2k

Looking at the wiring diagram you sent me (Thank you), looks like my terminals A and B are switched. MY MISTAKE!! That's what I get for not being careful! Can't try tonight. Gotta wait till tomorrow night. I'll let you know what happens.
 

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I switched the A and B terminals and it spins up like a dream. Many Thanks to Cal. Your help is greatly appreciated.

Mahalo!
 

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