I was working on an old British Locomotive (with rotor motor) for a friend who said the decoder had quit. Upon investigation I found the the contacts were dirty and the decoder works fine...However I found a .05mF capacitor across the + and - sides of the motor. The problem I found was that the motor had overheated causing the bearings in the plastic housing to melt throwing the armature shaft off centre and thereby causing the gears not to mesh properly and jam solid...
Do you thing the capacitor was the cause of the overheating?
Was the capacitor too small or too large?
Why the capacitor across the motor terminals? (Is that not a short across the motor?)
Capacitor is not needed. It's to comply with European RF supression standards.
DCC decoders work best with can and solid core motors. Any other type is a crap shoot where it might overheat and melt.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
DC controlled or DCC controlled? Apparently the loco has been running fine up until then. I would doubt the capacitor shorted but could happen as it happened to a piece of electronic equipment I was working on some years ago that shorted out a card used in a paper winding machine. Over the years, it has been very rare to see that type of capacitor short in my experience. I do remember the yellow body of the cap started to turn dark brown about the time the circuit breaker fired. There where many of those on the card for high frequency filtering.
The reason I ask is I have a Spectrum 70 ton DCC ready that had three capacitors hanging on the motor leads. The were not the polarized or electrolytic type.
Don't remember how they were connected as I removed them. I always remove any capacitors fom the Spectrum locos.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Thanks for the info... As it turns out because of the rotory motor melting the motor case and the age of the unit the owner will have to find a new motor or I will have to macgyver a new one into place which won't be easy... less the capacitor!
Yeah, the cap should go as well as any inductors in series with the wiring.
Good Luck on finding a motor for it. Modern can motors will work stronger and also draw less current.
Springfield PA
That cap didnl;t cause the overheating, the cap is there to supress RF emissions so your locos don't cause TV and raio interferences (although I never had an issue with this), but it ALSO supresses high frquency decoder drives as well as the BEMF signal if you use a BEMF decoder. FOr this reason the caps should be removed for DCC. It also appears these caps interfere with DC power systems that use PWM (same as a decoder), and the locos tend to run better without the cap.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.