I need help. I have a Prewar 204 and am trying to get the motor running. I have bypassed the E-unit by attaching one wire from the collector plate (pickup rollers) to one brush and attaching the other brush directly to the field. Armature appears to be fine and I have tested the commutator plates with an Ohm reader...no resistance. When I apply power the armature hums and sits there....and gets hot. It appears that the left brush (the one attached to the collector plate) is where the problem is. It will smoke a little if continous power is applied. I have changed the brushes, I have changed the brushplate. I have cleaned the gaps between the commutator plates. How can you tell if the field is bad or the armature is bad? Hoping for help...and wisdom.
Thanks
Check each segment of the commutator to the armature shaft. Should not have any continuity.
Bill
I need help. I have a Prewar 204 and am trying to get the motor running. I have bypassed the E-unit by attaching one wire from the collector plate (pickup rollers) to one brush and attaching the other brush directly to the field. Armature appears to be fine and I have tested the commutator plates with an Ohm reader...no resistance.
As Bill wrote, test each segment against the armature shaft, there should be no continuity, that is infintie resistance. Your wrote aboe that these is zero resistance between two commututor segements (plates). If so, your armature is bad. The resistance between any two segements should be about the same, somewhere in the range of about .5 to 2 ohms. If you need actual values, I'll have to check.
Being a novice, I am also ignorant. After going back to my multi tester, I adjusted the range and sure enough, I have resistance on the commutator plates of roughly 1.0 ohm. There is no continuity between the shaft and any one of the plates. Awaiting further instructions.
Now that you can measure resistance better, what is the resistance of the field winding?
Bob Nelson
If I touch one lead to the brush that is connected to the field and the other lead to the wire that comes off the field, I get a nominal resistance of .1 ohms. However, if I touch one lead to the brush connected to the field and the other lead to the ACTUAL field WINDING, I get an open field reading....no continuity at all...is that right?
The wire is insulated with enamel. Measure between the two ends of the field winding at points where the insulation has been removed and connections are made.
ok, if I test each wire coming off the field, I got resistance of approximately 1.7 ohms. Should I have that much resistance on the field? What does it mean?
You say "each" wire. Are there more than two?
No, there are only two wires. One on the right side front & one on the right side rear - these are the wires I tested...which begs another question. I have a 1684 which has what appears (at least to me) an odd wiring configuration. One brush is connected to the field and the other brush has NO connection. However, there are TWO connections on the field - one to the brush and the other to the E-unit. Does that mean that the brush with no connection is "grounded'? No wires were loose, so I am assuming that this configuration is valid?
As I understand you, you found just two wires coming out of the field winding and measured 1.7 ohms between them. Is that right?
There are several ways to wire a locomotive to a forward-neutral-reverse-neutral e-unit that will work. But leaving a brush disconnected will surely stop the motor. There must be some connection to something if the thing runs.
The usual Lionel arrangement is for one field wire to be connected to the locomotive frame and therefore to the outside rails. The other field wire, both brushes, and the pickup are connected to the e-unit, which connects the field to one of the brushes and the pickup to the other brush, but swapping the brushes every two steps.
The way you wired it for testing, that is, pickup to brush, other brush to one end of field winding, other end of field winding to frame, should have worked. Is there any chance that you connected a brush to the end of the field winding that was already connected to the frame?
I noticed that you said that you "bypassed" the e-unit. Does that mean you disconnected it from the motor? It is possible to bypass it without disconnecting it by putting the drum into the neutral position and shutting off the coil so that it does not step out of that position. Did you do one of those things?
Bob:
First, thanks so much for your help.
RE: lead testing. Yes, when I touched one lead wire to the one field wire and the other lead wire to the second field wire, I got 1.7 resistance.
RE: configuration. Yes, I thought it was odd as well. There is no evidence of solder on the one brush, so it appears that nothing was EVER attached to it. Weird, huh? My understanding is that the collector pickups go first to the E-unit, then to one of the brushes. The other wire comes off of the field, then to the E-unit, then to other brush. So.... I'm on the same page with you. Again, this is a whole other animal, not the armature problem I'm having with the 204 motor.
RE: disconnecting E-unit. Yes, I physically disconnected the E-unit from the motor...no connections whatsoever. Didn't know you could "shut off" the E-unit by putting into neutral. Also, you mention "shutting off the coil", do you mean just moving the E-unit lever out of the "on" position?
Ok, when I apply power to each ot the brush housings, the armature moves a half-a-click to the right and stops. I noticed that if I physically move the armature a 1/4 turn or so and then apply power it will advance ever so slightly and stop. Now for the interesting thing, about 40% of the time when I advance it, it reverses direction when I apply power...like the polarity is being reversed. Awaiting further instrucions.
Using your ohm meter, verify that neither brush holder is shorted to the frame. As you stated, one should go to the pickup roller, and the other to one end of the field coil. Just make sure it is on the correct end. From the pickup roller to the frame you should have about 2.7 ohms according to your stated measurements. If it is less than this, you have something wired wrong. From the sounds of your measurements, the motor is OK and you have it wired wrong. Also, putting power on something until it smokes is a bad idea. If you toast the windings on the armature or field, you will ruin the motor.
Bruce Baker
It worries me that you say, "when I apply power to each of the brush housings." You should be applying the transformer voltage between the brush that is not connected to the field winding and the end of the field winding that is not connected to either brush. Is that what you are doing?
Also, can you verify that in fact you have measured nearly the same resistance three different ways in the armature? That is, if we call the commutator segments A, B, and C, do you get the same measurement between A and B as between B and C and as between C and A?
[quote}RE: configuration. Yes, I thought it was odd as well. There is no evidence of solder on the one brush, so it appears that nothing was EVER attached to it. Weird, huh? [/quote]
On some Lionel motors, one of the brushes is grounded.We are all accustomed to Lionel's typical wiring scheme where one of the wires from the field windings is attached to ground. But Lionel did make some motors where there was a metal ear on one of the brushholders that ends up underneath the head of the screw that holds the brushplate in place. On these motors, that brush tube will not have any solder on it, as described above. On these motors, the long wire from the outside (end) contact on the 4 finger assembly goes to the non-grounded brushplate. and the wire from the center pair of contacts on the 4 finger assembly goes to one of the ends of the field winding. The wire from the 2 finger contact goes to the other end of the field winding. In this case, the field winding is not grounded.
That's good to know. I looked for a wiring diagram; but I could find only a mechanical drawing of that motor.
How about it, Jeff? Can you determine whether one of your brushes is in fact connected to the motor frame?
Bob,
It appears that the other field wire is actually insulated from the frame by a thin strip of gasket material and then sticks up in the back. Also appears there was some solder on this at one time. I am wondering if THIS engine, the 204, has the same configuration as the 1684.....in other words, one grounded brush....is this possible? How do I determine if the field is grounded?
Thanks again for all of the help....and insight
I take it from your response. "that's good to know", that the fact that the armature advances ever so slightly and then reverses when power is re-applied means nothing.
RE: commutator readings. Yes, the readings between A-B, B-C & C-A are all approsimately the same resistance
Sorry, my "that's good to know" was for the information that a brush might be connected to the frame, which could be the root of the problem. Can you measure the resistance of each brush holder to the frame (with the brushes or armature out) so we can check out that possibility?
Sorry for not posting a reply earlier, but work & other insignificant things get in the way and this ended up being back-burnered.. Also, I went off into the desert on my own to look at this again....Here's what I discovered: the two (2) engines that I have, the 204 and the 1684 have the same wiring configuration, i.e., one wire goes from the collector to the field and the other wire goes from the field to one of the brushes, or to put it another way, one of the brushes is grounded. I got the 1684's motor to work! But here's the rub...I could only get it to work if I took one wire from the transformer and touched the collector on the bottom and touched the other wire to the brush that was NOT grounded. If I took that wire and rubbed it against a wheel, any wheel, NOTHING.... no spark, no hum, nothing. I suspect this means that I have an open field somewhere on the frame....or it could be that I making that up.
Engine #2...the 204: this I could NOT get to work, when I applied juice to the motor the same way as described above, got hum and that's it.....however, the field winding got very hot...is it possible the field winding is bad? Or, to put it another way, what else could cause this?
Thanks again for any guidance you guys....and especially Bob...can give me.
From your last description, I think that the 1684 has a field wire connected to the wrong brush. Try moving it to the other brush. Then you will have one field wire connected to the pickup (as now), the other field wire connected to the ungrounded brush, and the other brush connected to the locomotive frame. So putting voltage between the pickup and the frame should supply current to the armature and the field in series, and the locomotive should run on the track.
For the 204, check your field winding and each of the brush holders to see which if any of them has any connection to the frame. Then we can see whether there is a sensible way to hook everything up.
Thanks for the VERY quick reply. Ok, since my last post I've gotten both motors running, but they are both doing the same thing regarding applying power to the wheel(s) and the collector. Nothing....zip... but both motors work just fine when power is applied as per my last post. I am trying to understand what you are saying about moving the field wire to the other brush....If I do that, aren't I just switching which brush is grounded? How does that affect the frame becoming grounded? I'll try it, but I am having a hard time wrapping my head around this......unless I switch the field wire connections...? Does that make sense?
To rephrase my question, how does the GROUNDED brush get connected to the frame? By default, isn't whatever brush that's NOT wired grounded? So either brush could function as a ground, right?
Ok, I rewired it so the field wire is going to the OTHER brush. Same thing, no go. Works just fine when I apply power to the pickup and the unwired brush, but no go when I put power to the pickup and wheels....there is something else going on here.
The brusholder without any wires attached should have a tab attached that extends over to the brushplate screw on that side. The brushplate screw should have an internal toothed lockwasher under the head. The lockwasher should make firm contact with that metal tab. This is the source of the "ground" I have seen some brusholders with that tab damaged.
Now it seems that neither brush is "grounded". Please do what I asked for before, disconnect the field of each locomotive from any brush that it is connected to and remove the brushes themselves. Then find whether and which of the brush holders and fields is connected to anything else, particularly the locomotive frame. After we get that inventory, we can continue with the debugging.
Bob & CW
Ok......IT WORKS! CW, want to say thanks on the tab suggestion. That was the problem. Wasn't grounded between the brush plate & the frame....that did it. Works like a charm now... Bob, thanks for all of your help getting me to that point....could not have done it without and I learned A LOT....Much appreciated.
Ok guys......next project....when I hook up the 1684's E-unit....nothing. pretty sure my wiring is correct and solid. But no response from the motor. If the drum is not making good contact with the fingers, could that cause this?
Thanks again
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