Atlas O SD40 runs slow

Thanks, looked again and see nothing. Box is marked DC. Both units were on the layout and show slight run time. The instructions say use only AC power, but again box label says DC.  We found no AC power packs for the layout, nor way to switch track power to AC.  There is no speaker in tank, only switch under unit is SMK / NO SMK.  Other 3 empty ....  I am confused 

Check the inside of the wheels where the brushes make contact. On older models, they have a tendency to seize up and not make proper contact with the wheels.

Checked, all good. The lights work and both units move, only very slow ... will change direction, just no speed.

When they run slow is there any motor noise like a buzz or hum? Do they jerk or just run slow?

1.  Have you removed either or both body shells ?  Perhaps the motors were rewired in series ?

2.  Do you have a roller test stand ?  Check to make sure that both trucks seem to turn equally [ and in the same direction.....]

SZ

Problem(s) solved!  Thanks for all the suggestions.  Had 2 problems ... Major # 1 was the momentum switch in my MRC 9500 got stuck in the on side without the LED being lit, a couple of slides back and forth and it back to normal.  While this took care of 75 % of the problem, I took the shells off and lubed the motors and drives and now both units run 100 %.  Thanks again to all who took time to write.  Bruce in Mount Airy, MD

PS: Not sure if I can post the link to the collection here if so, let me know and I'll post it ... OR ... if you want to see it, send me an email

Bruce Blackwood posted:

Not sure if I can post the link to the collection here if so, let me know and I'll post it ... OR ... if you want to see it, send me an email

Could you please send the link to my email (in profile)? Thank you.