Thank you for the advice. . I obtained an 80-watt power pack, And everything is now working very well.  Just have to make sure that all my old track stays clean!  My first foray into this forum; manythanksfor the quick, useful responses!

I'm using the original universal motor, but do not have a smoke unit.

I'm hacking my old American Flyer locomotive ("Royal Blue" 4-6-2 S-scale); I have converted it to run on DC vice AC.  I'm trying to use a Spectrum Magnum C90715 power pack; it will run the locomotive fine in the test stand, but after about 30 seconds, the power pack shuts down (i.e., a voltmeter across the output reads zero).  If I turn it off and I wait a few minutes, it operates again for about 30 seconds, with the same failure mode.  So two questions:
1) What's the rated power output on this power pack?  (There is no label with that info.)
2) Is there a thermal or other kind of cutoff inside the pack?
3) Does it sound as if I have a defective power pack?

Many thanks for any help; the reversing unit on the AF loco was unrepairable, and I'm trying to get it in shape to pass to my grandkids.