Modular 10ee speed control pot

I was having trouble with controlling the spindle rpm on my 1965 modular 10ee. So figuring it must be the max speed pot, ordered a new one from Monarch. After taking a good look at the pot still in the lathe, decided to look into replacing the six strand cable that runs from the pot to the module.

Opened up the module cover, and found that the six wires from the speed pot were dis-connected

What makes this even more head scratching, I had spindle rpm control from basically zero rpm to approx 1000 rpm even with this pot not connected. Above this approx 1000 rpm the spindle would accelerate un-controlled until it shut itself down.

Is there something else connected to the speed control knob that controls spindle rpm? Sure does not seem to be, but something was controlling slower rpm. I have been using it this way for over 6 months without any odd quirks except the limited speed control

Dale

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Dale

The speed control isn't just one pot, it's 2 pots. One pot controls the armature voltage, the second (connected) pot controls the field voltage. While the armature voltage increases to the maximum the field stays at full voltage, after the armature is at max voltage the field starts to decrease. This is done by having the second half of the armature pot shorted and the first half of the field pot shorted.

I suspect that what's you're seeing is a minimal armature voltage and some field change (assuming that the field pot is connected) causing the speed change, and when the field disappears the motor is running away (this, BTW, is a really bad idea and can lead to the motor disassembling itself). But there's really not a lot of description to go on.

rke[pler

I am aware the speed control pot is in fact two pots. None of the 6 wires that come from this dual pot are connected to anything. I have double and triple checked that these un-hooked wires are from this dual speed pot. I have had an industrial electrician look at it and he concurs that the wires attached to the speed control pots are not connected to anything else. Just the six wires in the module compartment not hooked up. this electrician is the one who brought up that there must be something else that is controlled by the speed control knob, which doesn't seem likely.

Dale

I think you have us stumped. On a modular the mechanical linkage goes into a box with bevel gears to allow the dual pot to be at 90 deg to the axis of the control rod. That is the only thing that controls speed. Sun spots and vodo if you were getting any speed control from the resular speed control knob and the pot is not hooked to anything,

Someone kluged something else in place??? However, if you had some control using the standard knob and NOTHING else but the pot is connected to it - I'm stumped.

Pictures may help, but what you are describing should mean there is no control of speed.....

Paul

X2 on pictures. Something else is controlling the speed.

Thanks everyone for your help. I was pretty sure there was nothing else hooked to the speed control knob, but wanted to assure my electrician. I dunno what pictures would show. The bevel gears for the speed pots are where they should be, the shaft the pots run on is as it should be, the ends of the wires in the module cabinet are just sitting there. If you can tell me what to take pictures of, and if Windows 10 hasn't messed with pictures like it has with attachments, maybe I can get them posted

Dale

swellwelder said:

Thanks everyone for your help. I was pretty sure there was nothing else hooked to the speed control knob, but wanted to assure my electrician. I dunno what pictures would show. The bevel gears for the speed pots are where they should be, the shaft the pots run on is as it should be, the ends of the wires in the module cabinet are just sitting there. If you can tell me what to take pictures of, and if Windows 10 hasn't messed with pictures like it has with attachments, maybe I can get them posted

Dale

Click to expand...

I guess that you might try a couple of things before taking random pictures - try disconnecting and removing the gear on the face of the cast case the pots are in and see if spinning the pot shaft manually changes speed. If it does then the effect is inside the case, if not then something else is connected to the speed shaft.