Dead Motor Replacement?

I had a PS1 F59PHI that had the same problem. The motor on one of the trucks was stuck. After turning it by hand using the flywheel it works like normal.

Do some more testing before you deem the motor dead.

FWIW, testing on blocks is a poor test.  Almost any dual motored diesel with tach driven cruise control will have the controlled motor running before the "slave" motor in that scenario.

Did you check the wiring between the motors, they should be in parallel.  Did you try the roller test at higher speeds, say 60 scale MPH?

If the motor gear and motor size (365 or 385) it can be used.  But you need to check for imbalance.  Don't discount that the tach motor is the problem motor and starts turning to soon.  I have seen this in 2 PS-3 diesels.

The fact it is bad in forward but fine in reverse could be gear lash or some other issue in truck too.  G

Spray CRC Lectra-Motive cleaner into the failing motor while it is running.  It is non-flammable and will clean the commutator of the debris from the brushes.  We use it at MTH and 50% of the time motor current will drop in half.  I check the motor current by disconnecting the board and using a filtered DC power supply with an ammeter.

Thanks for all the great feedback. Pretty sure the motor is dead. When I turn the flywheel by hand everything is fine. And the engine was working perfectly for weeks before there was trouble. It WAS jerking going forward and smooth in reverse but then the non-tach motor just quit. No matter how I apply power to the engine it won't turn. So I'm going to treat it as if it's dead, unsolder the wires and connect these to another motor to continue to troubleshoot. If the replacement motor spins, then I'll drop it in.

After I disconnect the wires from the current motor, is there a measurement I can make (voltage) across the wire leads that tells me that the motor is getting the correct power? It should be if the other motor is working.

Thanks

@Scott J posted:

After I disconnect the wires from the current motor, is there a measurement I can make (voltage) across the wire leads that tells me that the motor is getting the correct power? It should be if the other motor is working.

It should be getting EXACTLY the same power as the other motor since they're wired in parallel.

Over the weekend I failed . . . I removed what I think is the bad motor (non-tach reader motor). With a not very good old HO DC power supply I applied about 1.5 vdc and it spun pretty well. I took off the motor mount and reinstalled without the motor so I could properly run the engine with just the tach reader motor. Comes up fine in DCS and goes forward and reverse with just the one motor but not so great (still staggers a little). On the leads from the motor I removed I measured around 1.5 vdc when I command 5 smph. I then connected the leads to the motor I removed and no spin. I took a 365 motor out of another engine, installed it and no spin. I took the suspect motor and wired that in place of the 365 I removed from the old PS2 engine. When I applied power, I heard a slight pop then "ENGINE NOT ON TRACK". So I succeeded in NOT finding the problem AND for good measure killing an otherwise good PS2 board set (5 vdc/9 volt battery). Currently my PS3 is sitting on the test track with the shell off, mocking me.

Don't beat yourself up too much Scott.....it was a PS2 5V board, and they commit hari-kari at the drop of a hat!!!

Could have been just a coincident, and that 5volt board was ready to die, no matter what was going on.

Peter.....Buco Australia

If the tach motor is wound bad and starts turning at a very low voltage, the board things speed is fine and does not raise voltage.  It does not know the non tach motor is not spinning.  Basically the tach motor turns at too low of a voltage.  As I said I found this imbalance on 2 PS-3 diesels.  Live testing can be risky.  Touch the chassis with a lead and you can have poof.  G

Thanks George. I'm trying to decide what the next step is. It was running really well and then started staggering. I ordered a good DC power supply from Amazon and that will help a little more with troubleshooting.

@GGG posted:

If the tach motor is wound bad and starts turning at a very low voltage, the board things speed is fine and does not raise voltage.  It does not know the non tach motor is not spinning.  Basically the tach motor turns at too low of a voltage.  As I said I found this imbalance on 2 PS-3 diesels.  Live testing can be risky.  Touch the chassis with a lead and you can have poof.  G

Pretty sure it’s this one. No matter what motor I connect to the non tach motor leads it won’t spin a bit at the low voltage that the tach motor spins at. Ugh

@Scott J posted:

Pretty sure it’s this one. No matter what motor I connect to the non tach motor leads it won’t spin a bit at the low voltage that the tach motor spins at. Ugh

Be more specific please.  A working can motor like the Mabuchi 365/375/385 motors used in most diesels should be spinning by the time the voltage hits 2VDC and drawing no more than 150ma.  I took three out of my motor stash and tested them.  They were all running before I got to 2.0VDC and drawing between 110 and 140 milliamps.  Also, a minor variation in the performance of the two motors means nothing in actual operation.

A fun fact, after a drop of DeoxitD5 on the commutator of the three motors and they all ran at 1.0 VDC and were drawing less than 100ma.  Improved conductivity to the armature really does help!

Ok, being more specific is something I can actually do without screwing up. The motor I removed is a PH385. I checked that motor and three others, all older 365's with a my new DC power supply courtesy of Amazon. All were pretty much 2 volts and 150 mA just like you measured. One was spinning just past 1.5 volts. I also had one that was balky and it improved after a drop of Deoxit on the commutator! If I connect any of the motors to the engine motor leads they all spin along with the tach reader motor. If I install the motor so that the drive gears are engaged nothing happens until around 7 to 10 smph and by then the tach reader motor is spinning like crazy. I would say both motors read the right voltage at the leads but nothing moves non tach reader motor. It's like there is voltage without any current being delivered. Is that even possible?

Without seeing it, I can't say if it's the motor or gears.  When the motors were on the bench, did you do any tests lightly holding the flywheel to put a load on them to see if they seemed to have plenty of torque?

Did you try connecting the DC power supply to the motors when they're installed in the locomotive?  Just pull the plug from the board and connect to one motor with the DC supply.  Also, testing them individually while actually connected to the trucks with the DC supply should be telling.

John, I have repaired 2 PS-3 diesels that had this issue.  The tach motor was the issue.  It could run at a much lower voltage then the non tach motor.  So the non tach motor would not turn then bind on the gears.  Replacing the tach motor solved the issue.  There was a major imbalance.  G

@GGG posted:

John, I have repaired 2 PS-3 diesels that had this issue.  The tach motor was the issue.  It could run at a much lower voltage then the non tach motor.  So the non tach motor would not turn then bind on the gears.  Replacing the tach motor solved the issue.  There was a major imbalance.  G

Swap the two motors, should make things work again.

Not necessary.  Just the one. :-)

@GGG posted:

Not necessary.  Just the one. :-)

I didn't say buy two motors, just swap the existing motors.

Well, I did connect the non-tach motor to my dc power supply and at 2 volts it spun nicely and even turned the wheels at about 1.2 volts. So I guess I'll go after the Tach motor next. However on previous checks, the tach motor starts moving when I advance the thumb wheel to 1 smph. So I would think that the non tach motor should be turning as well. Not waiting until 7 smph and struggling to move. I'm wondering if there might be a problem with the wires from the board to the motor.

I'll say it the final time.  It is normal for the non-tach motor to lag the tach controlled motor, it all depends on the specific friction encountered in the drive train.  It's actually rare for both of them to start at the same time on a test block.

If you put a 10 ohm and 5 ohm resistor in parallel which resistor gets more current at a given voltage.  There is a lot at play here.  Once a motor starts turning and the engine moves the wheels on the non turning motor move but th worm gear doesn't. You now have some bind on the motor which means it needs even more current to start moving.

This is similar to what can happen on a Slaved diesel.  Seems the E-8 are the most offending in this category.  You have to clean both motor commutator and brushes with spray.  Check the gear lash of the trucks, and lubricate properly to get them back in balance.

For the 2 PS-3 engines I saw this problem with the tach motor had a lower winding resistance then the non tach motor.  You can measure and test all you want, in the end I put a replacement motor in for the tach motor and it was fixed.  When the second engine came it I replace the tach motor first and it was fixed.  G

I finally yanked the tach motor. Definitely not the same as the others I tested. Spin starts at lower voltage and it draws 200 mA at 2 volts. The obvious next step is to try a different motor set up for a PS3 tach reader. Do I have some PS3 engines that I would sacrifice to the tach reader motor? Yes. Do either of them have the right size worm gear? No. And from what I've read the gears are not removable. So for now I'm going to put the whole mess on the shelf and work on something more in line with my capability like lighting and scenery.

200ma at two volts is normal for a Mabuchi RS-385 in good condition, I seriously doubt there's anything wrong with that motor.  I have a whole gaggle of similar motors that have similar power consumption.

Well if it's not the motor it is certainly above my skill level. If both motors should have the same voltage the motors should both be turning at 2 volts. I can pick any motor and connect it in parallel to the tach motor and the tach motor is flying and the other motor won't budge. I'm also not seeing any delay with other engines between the motors. Both motors start turning as soon as the thumb wheel is rolled up to 1 or 2 smph. If the tach motor starts first then it's very hard to see. Regardless, the engine is broken. I will eventually try another tach motor just to be sure.

If you have a Mabuchi RS-385 that's not turning at all with 2VDC applied, I'd be looking closer at that motor.  I just took six assorted Mabuchi RS-385 motors out of my parts box, all of them were spinning by the time my P/S got to 1.6 VDC, and humming along quite nicely at 2VDC.  None of them were over 200ma power consumption, but they varied from around 130ma to 190ma.  FWIW, I find that a shot of DeoxIT D5 on the commutator drops the current on most of them to lower values, one got to 110ma at 2.0 VDC.  A drop of oil on the axle bearings frequently helps as well.

And it is NOT the motor. I connected another motor with a tach flywheel and was able to attach the tach reader in the right location. Powered up the engine and got the exact same result. It's very odd. If you touch the flywheel on the motor that won't spin you can feel that it is getting powered but it's like the motor is paralyzed. And it's not mechanical. I powered both motors off of a DC power supply and they ran together and turned the engine wheels very smoothly. And it's not the motors. I would try a different tach reader but cannot find where it plugs (if it does) under the giant pile of wires. Crap. I did try though. George and John, thanks for all the feedback.

I would get another 8 pin harness.  Has power and motor leads.  Swap it in and test again.  I would guess a motor lead is damaged and can carry minor current and show continuity but not allow full current flow.  I have seen grounded motor leads and I have seen that in steam harnesses, but not on a diesel motor lead.  Maybe a full kink, or crush somewhere.  G

I have my doubts that it's the tach reader.  If the motor with the tach is not running away, it's getting the tach signal to the board.

I'll say again, the two motors when they're not on the track will very rarely run at the same speed or start up at the same time, this is totally normal.

You want a simple test to see if the second motor will pick up the slack?

Grab the tach flywheel lightly and put a load on it.  As the current and voltage goes up to handle the load, the second motor will also receiver more power, and like magic, it'll be running.

I gave it the last rights for now. My best option for repair is to pull the PS3 set out of another engine. Probably the AS 616 I have that has always been a DCS bad actor. Then a sound file change. This has been a weird one for sure. I have had some early model PS2s up and die but have never had a PS3 fail on me like this. Quite a few hours of excellent performance and then this. Thanks for all the helpful advice. I sure know a lot more about Mabuchi DC motors!