DC motor troubleshooting



Likely, but you would have 50 volts across either one, open circuit or not.

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    Actually -- the *motor* itself has your four terminals/wires, A1, A2, F1 and F2.
    The wiring from the driver/power-supply/WhatEverYouWantToCallIt is three wires. One of them goes to one Armature terminal, one goes to one Field terminal, and the third wire goes to both the remaining Armature and Field terimnals. They're saving one wire, and tying together one end of the Field and one end of the Armature power, a common low voltage point for both.
    Perhaps the currents are too high in the ones which you work on to allow that sharing of leads. But his is not nearly that high a power, and perhaps the distance from the motor to the supply is long enough so it is worth while doing it that way.
    Good Luck,         DoN.
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Common ground externally excited field shunt motor.. Speed changes as the ballance between the feild and armature changes - the stronger the field, the slower the engine.
To test the motor check continuity between f1 and f2, and between a1 and a2 with the motor assembled. If you have armature continuity and not field continuity, you are likely to burn out the armature quite quickly as the armature will be pretty close to a short. An open field is pretty well indicative of a burned out field.
If the armature is open, turn the motor and see if it is intermittent. If so, the armature is burned out. If not, there is a bad connection from either A1 or A2 and the brush assigned to it.
Really a pretty simple thing to test - not necessarilly easy to fix..
If you have continuity on both, connect a1 to f1 and a2 to f2, and connect jumper cables from 12 volt battery to the a1f1 and a2f2 connections and the motor should run.. Connect a1f2 and a2f1 and the motor should reverse.
If that works, your "drive" or controller is damaged.
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Yep. I will check all that tomorrow.
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On Sat, 11 May 2013 17:50:58 -0500, Ignoramus9202

Check the armature. (My VOM has a beeper mode which speeds things up in cases like this.) Opposite commutators usually connected by a winding (180 degrees apart when the brushes are set in that position.) Also verify that none of the commutators are shorted to the shaft, then verify that the commutator is connected to the wire it's supposedly soldered to. Sometimes the brush can wear off the solder and lose a connection, but that just ends in a motor which won't start in certain positions. Verify that each brush and its connector are actually intact. Some had carbon rather than wire inside and it can degrade.

Logically, as you usually do. :)

Sometimes it's just dirty and cleaning/reassembly fixes it. Do the individual tests. If you find nothing, assemble and try again. I've brought home dozens of "broken" or "burned out" electrical products which had a grain of sand between working and not working. I've made hundreds (if not thousands) of dollars reselling the working product.
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Yep. I will post updates when I am done figuring it out. Thanks
i
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Ig, It's somewhere near worthless and a waste of time to post any details until you get it solved.
Ig, it's apparent that some folks refuse to read your first post, wanting instead to make the problem fit their solution. However, three people all suggested the same, useful thing.
Ig... those who suggested checking continuity between the "A", leads and the brush holders shouldn't have had to make that suggestion. That check should have been a natural part of your protocol to begin with, as soon as you saw power to the A leads, but none on the brushes themselves. (just a small finger-wagging <G>)
LLoyd
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On 2013-05-12, Lloyd E. Sponenburgh <lloydspinsidemindspring.com> wrote:

You are right. I decided to take the stator off and wash it before proceeding, due to it being extremely dirty.
i
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It would be worthwhile to include more details in your posts, as you've been criticised for previously.. so days later someone may realize what it is your talking about.
This drive got a name, p/n, or voltage marked on it? Someone may have a schematic/wiring diagram or other useful info for a similar drive if you would give details.
It appears that a voltage is present for the field (but it may not be the correct voltage). The motor also needs an armature voltage A1-A2.
The armature voltage isn't getting to the armature. Failed drive circuitry. Switch device open. Half-assed previous repair/anything. The armature voltage is the one that's controlled by the circuit.. any of the components associated with the motor speed could have failed. I've read more than a couple of times that speed pots had failed in a certain table drive.. Enco maybe. There may be some info and/or a schematic in the dropbox archives.
It may be that the drive motor runs all the time because it failed before and some motor monkey found a way to make it run.
You've seen considerable wear present, but you'll likely spend hours trying to make the old drive work, possibly poorly or only briefly, then hold out for another used drive for cheap. Possibly you were thinking you'd get an old machine that you'd be able to use for years without ever spending a dime on it.
The machine probably didn't cost much but if you aren't willing to spend some money on it, you probably just dragged it back to scrap it.
Plan B.. put a handwheel on the feedscrew.. which is a good plan, that may even dissuade the operator from walking away from an operating machine.
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