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Discussion Starter #1
I purchased a Santa Fe 484-485 and 486 used. I thoroughly cleaned both chassis on the 484 unit removing petrified grease and crud. One of the worm gears was stripped. I replaced it with new. Axle holes on both motor units were good. Armature bearings were good. I replace the brushes on both motors and lubricated both motor armature bearings and gears properly. I replaced both thrust pads on each motor. I disassembled and cleaned the reverse unit and replaced both fingerboards. Checked all wiring connections and resoldered the old ones. After my first track stand test The motors ran okay forward and reverse but there seem to be no high end power. I then replaced both brush holders with brand new and new brush springs. The track stand test produced a little better results but I could Tell it wasn't reaching high enough RPM. I reassemble the body to the chassis for a test on my layout. The 484 ran okay by itself but nothing to brag about. I added the 485 and and 486 units. The 484 struggled to pull them around the track. Again I dismantled both motors checking all wiring centering of the armature in the field and I'm still having the same problem. Do these alco armatures tire after a while? The only test I did not perform was an ohm test on the commutator of both motors. I didn't feel it was necessary because both motors are running evenly but are not getting the power that I'm sure they have. I think I have exhausted every procedure possible except replacing armatures and I really don't want to go there if I don't have to. Any thoughts out there?
 

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The only thing you have not done is meter the three armature windings to see if there is damage. They should be 1.9 to 2.0 ohms and all three should be the same. The armatures in these engines should have skewed poles and the commutator slots should align with the open ends of the core stacks. If the motors were stalled with the voltage on it is easy to overheat the armatures and damage them. With traction tires the wheels will not slip and if the motor was not kept clean it is easy to stall the engine with a string of cars connected. If you check the field resistance it should read the same as the armatures.
 

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Discussion Starter #3
Thank you for your reply. I have dismantled both motors and metered The three armature windings on each motor. The readings were two ohms for both motors. I metered both fields and got a reading of 1.3 ohms on each. However I did not remove the red and black wires. Then I snipped off the red and black wires and got a reading of 2.2 ohms. Not sure I did it right.
 

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If you really want to dig into this problem here are some more thoughts and tests. The first post said the fields were centered. When I disassembled my 370 motor it took me close to 10 tries at fine tuning the screws to get the motor to run properly, this was after it looked centered to the eye. Maybe I am just a lousy tech. Try spraying some contact cleaner on the commutators while the motors are running. If they speed up a lot then there is either a spring tension issue or the brushes are not properly bedded to the commutators.
The basic symptom here is the motors seem to not be producing any torque. An electric motor produces maximum torque at zero RPM so as the engine slows down current draw increases (less back EMF) and the motor should not stall. If you have an AC ammeter check the current draw with the engines on the track with some cars for load, Then with 12 to 14V on the track the dual motor engine should draw 4 to 6A at very low speed or when starting out if working properly. As the train speeds up the current draw should drop to around 2 to 3A. I suspect the motor is not drawing the full current needed to run properly. High brush resistance or improperly centered fields will cause this. If there is mechanical binding the opposite will happen. Current draw will increase, the motors will run slow and get very hot.
 

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Discussion Starter #7
I have these two meters. I do not know how they work other than to test for resistance. Is one or are they both AC ammeters? What do I set the dials at?do you apply the probes to the track to get a reading? I am not much of an electrical technician.
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Do not use those meters to measure AC amperage. They are both for DC amps only plus the top one has a maximum of 1ADC. The Cen-Tech can measure up to 10ADC so it has adequate range. If you have a DC power supply you can power the engines with it to measure the current draw. The DC power pack would need to be rated at a minimum of 75VA, which leaves out most HO power packs. The other choice is to buy a cheap minimum 5A rated bridge rectifier to run the track feed through.
 

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There is another way to get a rough answer if you have a known good dual motor A unit. Couple it up to a train and run it around the layout 10 times at high throttle. Stop it and touch the motors to see how hot they are for reference. Do the same with the engine that is running slow. If the motors are a similar temperature there is an electrical or field alignment problem. If they are much hotter then it is likely mechanical binding.
 

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Discussion Starter #10
Where do I check for temperature. Do I touch the field or the brush holders? From various track stand tests I already know the brush holders get too hot to touch however I never checked the field or anywhere else. I will try it again. Thank you for helping me through this. It's been very frustrating.
 

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I do not recall the brush holders on my diesels becoming too hot to touch. It has been a while since I worked on any of the diesel engines. I want to get out a dual motor and run it to see how hot they get. I will get back to you.
 

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The first dual motor PA I found was a 1956 490 Northern Pacific. This engine is all original under the shell except for lubrication and commutator cleaning. I put it on the track and it took off around the layout.
I then removed the struck sideframes and then the shell. Without the sliding pickups on the sideframes the engine did not run as well, there was some sparking at the wheels and some sparking at the commutator of the rear motor. With clean wheels and track sparking at the wheels indicates wear at the truck axle holes. In this case not yet enough to affect performance with the sideframes on. There was no sparking when I put the sidframes on because the sliding pickup shoes bypass the wheels and axles for power pickup.
The sparking at the commutator indicates inadequate brush spring pressure. Sure enough, when I squeezed on the brushes the motor sped up and the sparking stopped. Squeezing on the brushes of the front motor had no effect but there was no sparking so its spring pressure is good. The brushes were too hot to touch for more than a second, but no other parts of the motor were hot. This engine has a good slow speed range and at 12V it is FAST.
 

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Discussion Starter #13
I reassembled the 484 and put the side frames on. Not the body. As a test I first ran my 21925 and 21925-1 along with four passenger cars for 10 minutes around the layout. Using an infrared temperature gun I obtained an average temperature around the motor of about 94°. I then removed the 21925 dual motor and replace it with the 484 and ran that for 10 minutes. The average temperature of the two motors after 10 minutes was 87°. And there was no sparking. I did fiddle with the center ing of the 484 before the test. On the rail stand test the front motor seem to be going at a higher RPM than the rear. All in all on the layout test the 494 did run better but did not blow my skirt up. It took 5 seconds longer to make the complete loop than my 21 925. According to the 1957 catalog the Santa Fe 484 should be able to pull up to 40 cars. I don't think so.
 

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Did you try lightly squeezing on the brushes to see if the motor speed increased? If it does you can bend the spring a bit to get more spring force on the brush holder. It sounds like the 484 is running ok. The 5 digit engine likely has the revised 3rd gen armature with the straight rather than skewed armature poles. They are direct replacements for the skewed pole armatures should you ever need replacements.
 

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Discussion Starter #15
Ok, I squeezed the front and rear brushes and both motors picked up speed. As I mentioned earlier in the post I did replace both brush brackets and new springs. I remove the motors from the brackets and bent the springs as far as I could without distorting them. Still not much change. Again I squeeze the brushes together and both motors picked up speed.Should I try bending the brush holders toward the commutator?
 

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I have never tried that. I think bending the holders may just cause misalignment and make things worse. I have fully recalled why I quit running these diesels except for a few hours on a Christmas layout! When they are great they are great, when they need repair they seem to be impossible to get right. The Gilbert steam engines are much easier to keep running right, for me at least.
I am happy running all newer Legacy engines on my layout. They sometimes need service. All I have to do is drive them to the UPS store to send them to a professional, they are returned better than new with no work on my part.
 

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Discussion Starter #17
Totally agree. I am at that point. Can't thank you enough for your time and your input. Thank you again. Do you have the name and email address of a professional I could use?
 

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I do not know anyone near you, or for that matter near me. You could email Ed Goldin at Goldinhands.com and see if he can take it on. He currently has one of my AM E8's for repair. Last I spoke with Ed he had about a 6 week backlog. Ed is in Schaumburg, Il. and his email is [email protected].
 

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I do not have any old AF diesel. I regret that but I have heard how contrary they can be and I have avoided them. flyernut calls them "finnicky". That's enough for me.
 

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Discussion Starter #20
Finicky indeed! After hours and hours of trial and error and a good night's sleep I think I fix my problem. Noticing that pinching the brush holders increase the speed of the motor and not wanting to misalign the brushes by bending the brush holders I noticed that by pushing on the tops of the brush holders where they go through the top of the brush plate the speed of the motors increased. I decided to bend the top of the brush holder down toward the brush plate just enough for the brush spring end to slide underneath it. This still did not fix the problem. I realized that if I could make a small wedge and slide it underneath the top of the brush holder it would put more pressure on the commutator. I took some heat shrink and molded it into a small wedge after heating it and slid it under the top of the brush holder. Low and behold it worked. Good old Yankee ingenuity.
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