Railking Imperial GS-4 had just gone through a complete PSA cycle, but refused to begin accelerating on its own, as it normally does when PSA is engaged conventionally, while the engine is in motion.
Nudged transformer lever up (from the 12 volts during PSA) to 15 volts, and it took off like a shot, no more chuffing and no speed control, and jerked to a stop. Then it continued in a cycle of run fast and stop, every few feet, all on its own, while voltage was held at about 11. Normal for this engine is 30 scale MPH @ 17-18 volts (with speed control).
Tried factory reset and speed control on/off–always geting the two toots–but to no avail: no speed control and the stop and go continued.
Took boiler off, but nothing looked amiss, and since the warranty is still in effect, I sent it off to MTH.
Does it sound like a board went south? or…
Edit: also checked in tender, as well.
Sounds like you have a bad tach reader. This simply reads and counts the stripes on the flywheel. It’s needed for cruise, smph readouts as well as chuff rate.
What Dave C said. Sometimes the reader can move just slightly and not be able to read the stripes. It might not be bad just out of place.and that seems to be a hit and miss fix until you find the right spot. still under warr. let them do it.
Thanks guys,
Tach reader, huh. It just surprised me that after about seventy hours of flawless running, it spontaneously went cuckcoo. But hey, I can understand that–some days, my tach seems off a tad, too. [(-D]
Above the striped Encoder Flywheel is a small PC Board with 3 fine wires comming out of it. The gap to the flywheel should be 0.75 mm. Also, I have had one of the wires break, it can be re-soldered with a low wattage soldering iron.
The “Tach” is really a “Binary Encoder” giving a series of “0” and “1” pulses. If the micro-processor does not see the pulses comming in, it thinks the motor is not turning and increases the power to it until it reaches full power (speed).