MTH Mabuchi Motor Voltages

I don't think they changed voltage, but I have found resistance differences that can affect dual motor operation.  End of last year new PS-3 diesel that one motor would not turn.  Assuming it was bad replaced it and still did not work.  Turns out the tach motor was the defective motor with low resistance and would run on lower voltage than the non tach motor.  Effectively consuming all the power leaving the other motor to starve for current.  Once I replaced the tach motor all was well.

PS-2 Slave can be real problems and I have seen differences in truck gear lash bind a motor, let alone any imbalance in motors.  Ultimately it can lead to a stall and one of the reasons the slave motor fet may fail.

I would take a DC power supply with a good voltage and current meter and test those motors for break away voltage or stall.  And current draw at a set voltage.  Fine the best pairs.  (Blue print in car terms the chassis motors).

As far as worm.  They must be the same diameter and length to match the truck.  There are some variations that can lead to more back lash and potential issues in allowing the axle gear to lock the motor worm and making it even harder to get spinning.  G

@Jeff_the_Coaster_Guy posted:

Now I'm wondering if maybe MTH used 24V nominal motors in some premier engines, but 12V motors in the ABA sets to reduce power demand?

Actually, a 12V motor would likely have a larger power demand at a specific voltage as you'd be nearer to it's rated maximum voltage.

Thanks George.  I might do what you're suggesting for the master A and just find 2 good motors.  But I'm thinking maybe it's not even worth it to install the motors in the slave unit.  I don't pull trains long enough to actually need 4 motors anyway, and sounds like it might just be more worthwhile to keep those motors for another project and make it a dummy.

UNLESS...is there any reason that connecting the ABA as a set but NOT having the slave unit motors operational would mess with the PS2 system?  Should I maybe remove the pickup rollers from the slave unit, or are those needed for the lights to function properly? 

You could remove motor but leave rest of slave connected.  Yes slave needs pickups.  G

@GGG: Revisiting this. Dad really wants this consist working properly with All 4 motors, but we can't get it to stop stuttering say low speed. I actually bought and installed all new motors from MTH but still have the issue.

Do you think it's something I could send to you to diagnose and see if it can be fixed? Maybe the electronics are bad, but everything functions properly otherwise.

Or do you think that the problem is not worth going after, in which case I will pull the motors in the slave (not Dad's preference).

What motors did you get?  Revisiting, are all the worms the same this time.  Does the lead truck non tach motor lock up too?  This sounds like worn out trucks possibly.  That originally was a PS-2 5V.  Seems this can get real expensive.  The time I would have to put in to track this down would not be worth it.

Unless your missing something obvious.  The fact the lead doesn't even run right by itself would be problematic.  G

I'm about 15 months late to this thread.

All of the Mabuchis that I've seen in MTH diesels begin with RS-385PH.  There are additional numbers on the labels which are a build code or batch number.  They might reflect customizations like a higher-voltage winding, different brush materials, etc.

GunrunnerJohn is exactly right that 24-volt winding would have LOWER current draw (and rotational speed) compared to 12-volt.  However I don't think mismatched voltages are the issue here.  I have the first set of Premier FTs with Proto2 (20-2345-1.)  I bought it new with its original motors.  Since new it exhibited "chuggle" at the slowest speeds, where the motors seem to start and stop until they get enough voltage to consistently overcome transient frictional events.  It's noticeable.  You can see the trucks moving relative to each other at different times, and the knuckles between the units stretch and bunch.

The flywheels are too thin to be really useful (probably due to lack of headroom in the compact FT), and there's only so much PS2 can do.  The gears are self-locking, so when a motor stops, there's no way the other motor(s) can "push" it, they just have to wait until it gets going on its own.  I believe this is one of the reasons Lionel switched to back-drivable gears in their Legacy LionDrive diesels, and I don't see any chuggle with my 6-34589 or a Legacy GP7 that I tested.

I was disappointed with my FTs, so I called MTH tech support.  They offered to sell me extra motors, if I wanted to experiment and find some that were better matched.  I decided that given the small flywheels, tall gear ratio, and self-locking gears, this behavior is a limitation of the design.  I concluded that if I REALLY wanted the smoothest possible starts, I should keep only the better motor.  That's right, a radical motor-ectomy!  Probably not what you hoped to hear.

I've also heard that MTH won't perform warranty repairs if the loco runs smoothly at 5 scale MPH in DCS.  That's about the best mine can do.  In your case 15 MPH, wow.  If you really want to break the bank, and you have some engineering skills and patience, you might be able to replace all four motors and trucks with the corresponding parts from a LionDrive E-unit passenger diesel.  I think the complementary back-drivable gears would give you the smooth operation your Dad is hoping for, but at what cost?

@Ted S posted:

I've also heard that MTH won't perform warranty repairs if the loco runs smoothly at 5 scale MPH in DCS.  That's about the best mine can do.  In your case 15 MPH, wow.  If you really want to break the bank, and you have some engineering skills and patience, you might be able to replace all four motors and trucks with the corresponding parts from a LionDrive E-unit passenger diesel.  I think the complementary back-drivable gears would give you the smooth operation your Dad is hoping for, but at what cost?

MTH only states 5 scale MPH as the lower limit.

Ok seems like the solution is to pull the motors from the trailing A unit and make it a dummy, which I'm fine with I suppose.

@Ted S your description makes total sense. With the big ratio in the worm, I can totally see how the motors can fight each other due to self locking and the inability to backdrive the lagging motors. I'm guessing this would happen with just about all of ABA sets of this type then. Surprised I don't hear more of it.

Thanks for your help guys.

Another solution is to make the trailing powered unit independent.  I just finished up a pair of Lionel Legacy upgrades to a set of MTH PS/1 E8 engines.  The two are totally independent units, each with their own Legacy RCMC and RS-Lite.