PW 681 Problem

Run the engine with the boiler off and observe the e-unit.  Make sure the drum is being rotated with each power application.

Try pushing each of the fingers against the drum with a pencil to insure they are making good contact.  You may have to interrupt the power once to insure the engine is not in neutral.

I agree 100% with the previous poster to clean the brushes and brush holders.  And while it is apart, clean the commutator plate too. 

Assuming that you have good electrical connections, this should either correct or identify the problem.

Earl

Are you certain it's an electrical problem?

I suggest checking the mechanism for binding.

Something may have gotten into the gear chamber.

The smoke unit cam / lever may have issues

The magnetraction magnet may have picked up something.

Thanks for the input I'll try your suggestions later on and see what happens, I thought everything was solid so I will recheck what I did. 

Also: Sadly, some of the e-unit replacement parts that have been on the market over the past few years are not made correctly. Some of the problems I've seen include:

drum contacts mis-aligned.

E-unit fingers too long

E-unit fingers fiber board too thick to fit into the slots in the frame.

If the motor is buzzing, the eunit fingers are making contact. If they are not, the motor will not buzz.

I guess that certain e-unit fingers could be shorted to the e-unit frame.

If it moved and then went into neutral,it could be something on the track or the pick up rollers. Something such a dirt or a gap in the track may be just enough to activate the E unit. Again, try with the shell off. If it goes into neutral, try to activate the unit by slightly touching  the wires with a screwdriver. Good luck.

Hopefully, it'll be an easy fix, like the E-unit or maybe a brush problem.  You don't want an open winding on the armature.

I assume the buzzing he is hearing is the e-unit rather then the motor.  He can verify if the e-unit is the source of the buzzing by moving the e-unit lever to the opposite side and see if the buzzing stops.

Earl

A little while ago I checked to see if there were any obstructions and everything seemed to be fine, it will roll freely by hand.  I then took apart the pickup rollers and cleaned them and replaced them.  I put the thing on the track and it would lurch forward for a couple of inches and stop and just the eunit buzzes.  If I nudge it a little it might move a couple of inches and then stops again and buzzes.  Does anyone have any other ideas to help me out?  Maybe just a bad e-unit period?

I am thinking E unit at this stage. But, have you cleaned the brushes and brushplate and armature?

Rob

I just cleaned the brushplate and armature and viola it is running again and pretty good too. Thanks guys for all the advice.  One good thing out of all this is I did a ton of things I wouldn't have tried normally on my own, especially working on the e-unit.  Now I have more confidence working on these things and not running to the LHS everytime something happens.  Also my profanity improved and I think I can claim that as a second language on a resume lol.  Thanks everyone again

This happened to a 681 that I bought at a train show, exactly the symptoms you described.  As you have already discovered, it just needed the brushes/brushplate cleaned, and it's been running perfectly ever since.

It seems that the 681 may be particularly susceptible to this problem, which is, fortunately, very easy to fix.

quote:

I assume the buzzing he is hearing is the e-unit rather then the motor.  He can verify if the e-unit is the source of the buzzing by moving the e-unit lever to the opposite side and see if the buzzing stops.

Good point!

Don't forget about the oil hole on the upper side of the motor case. Try taking the armature out and clean and regrease the bearings. This made my 681 use 1.5 volts less to run at the same speed as before.

Rob