Motor Over Current in one direction?

[CPRail]

Happy New Year Group!

I'm installing RP in an old Athearn BB SD40-2 which I've re-powered with a motor from a surplus Proto Power West chassis I had kicking around. The re-power was needed as I couldn't get everything to fit in the shell with the old Athearn motor (too tall).

After installing the motor and hooking everything up (including a LM-2S with the associated bridge rectifier to allow for the inclusion of a TCS KA-4 keep alive - all connected to an Athearn board through the 9 pin plug), I went to test it.

Forward motion, everything is a-ok, motor runs like a dream. Switch to reverse, I get a Motor Over Current with the tiniest of power applied - like 0.1% throttle. I disconnected the leads from the motor to the board and tested the motor, no problems.

This was truly a WTF moment. Any thoughts?

[Gibs]

Here is one possible cause.

I know this may sound odd, but sometimes when a motor has been run in one direction most of its life, the brushes get out of shaped over time in a bad way so that when its put into reverse, the brushes are contacting more than one section of the commutator at the same time - ergo short. Its not usually a big deal as you can power through it usually if its directly connected to power, but with a RP Module in the mix, not good.

Fix (if this is the issue) - is to put some jumper leads directly onto the motor so its running in reverse from a good strong DC supply of 12V-16V DC and disconnect the LM from its plugs before doing so. Let it run for a few hours and then try again.

If its still chucking a wobbly then the brushes may need to be replaced and the spacing's on the commutator cleaned out (be easier to replace the motor).

Another cause.
The Brass Sintered journals have dried out to much and can only handle the most used direction of rotation. Replace them (again replacing the motor would be easier )

[CPRail]

I can give that a whirl, but I'm not sure if that is a factor with a can motor. Nothing venture, nothing gained!

[gregeusa]

I agree to look into what Gibs said... perhaps remove the motor, or pull the trucks and measure current in each direction.

Pretty hard to get the drivetrain to be direction dependent, but again I agree with Gibs, it is possible and I have seen it a few times, but mostly steamers with side rod / quartering issues.

Good luck.

[CPRail]

Further info:

It throws this error regardless of being connected to the drive train or not. Binding in one of the trucks was my first guess, but no avail. You can see in my photo that the drive train is not hooked up, and I was still getting the error.

Prior to repowering/RailPro, this engine was a good runner with no issues apparent.

[KB02]

Another thought: Bypass your PC Board. If you happen to have a spare 9 pin laying around, hook up track power and motor leads directly to the harness and then plug in your LM. Give it a whack that way. It's possible the problem lies in the motherboard where some logic controlled circuit is not playing happily with the LM.

Worth a shot anyway. It would rule out both the motor and the LM a sources of the issue.

[CPRail]

Thanks Gang!

I hope to try all these options later this weekend. This loco has been languishing on the workbench for too long, so I want to get it into service!

Stay tuned.

[CPRail]

Hi Gang,

Before I tried anything else (as the install is mostly done), I figured I'd swap out the LM for a verified new LM-3S, just in case. Guess what? No issues with a new LM-3S!

Looks like the LM-2S is buggered. I can't recall if I pulled this from a loco that's been disposed of, or if it's a used one I picked up. I'm guessing the later, especially as the other used one I got was dumping excessive voltage through the speaker when connected. Cooked 2 speakers figuring that one out! It works good for driving my turntable though.

Do you think Tim Ring would work on it (for a fee), or do I just chalk it up to lesson learned? The cost of repair (including postage) might exceed a new LM-3S.

Thoughts?

[faithie999]

it's been a while since I sent a module in for repair, but Ring did the repair for what I thought was a reasonable price.

ken