Hello;
I had a derailment and short (and smoke) from the subject decoder and constant short whistle soundings. I let the unit cool off and the next day it ran fine. Haven't run it for a few weeks. Now with power on the layout both front and rear headlights are on. When I try turning them off the engine starts making normal operating sounds and the short whistle bursts. According to the manual this indicates too high track voltage. My power pack AC output to my NCE Powerpro is 17.1 to 17.5 volts. Close to the recommended max of 18V. Other engines run fine and never a prior problem with this one.
Is this a decoder replacement or an onboard resistor replacement? Does QSI have any warranty program? If I replace should I go Tsunami?
Thanks in advance.
Mark
Mark.
Shorts can do some very strange things to decoders. I have one that goes into maximum momentum even when not involved in the short itself. Try to do the manual reset either with the reed switch or better to do the 3 CV reset and then try it on address 3.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
If the decoder smoked, at the very best, some component is now marginal if it wasn't outright destroyed.
Also, the fact that a derailment allowed a short through the decoder means that something isn't properly isolated in the loco. I don't have any Proto steam locos but I'm goign to guess that the loco frame is connected to one of the motor leads, or something similar. This would allow a derailed wheel to press between the track and the frame, connecting track pickup to motor output which is always a Bad Thing.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
If nobody, especially the OP, would mind the aside, I would like to ask why a DCC base unit's short detection component would allow the surge in amperage that would have cooked either a properly or an improperly installed decoder?
Randy?
Selector.
Not knowing how the layout is wired and the circumstances of the derailment. There are some ways that the booster will not shut down. One is not enough or poorly soldered feeders where the resistance is great enough that the booster does not see the short. Another way I have seen decoders get fried is a short reversing section where the auto reverser is constantly switching polarity instead of seeing a short and tripping. Another is having an under powered power supply where there is not enough amperage to shut down the booster. Then there are the internal shorts in the locomotive. If the motor is not totally isolated from the frame and a wheel should happen to touch it then poof goes the decoder too. Lighting sections of the decoder can fry if the lights get shorted and the same can happen to the sound amplifier if the speakers are shorted.
All too many layout builders do not do an all important quarter test. The most common reason the decoders get fried is the booster not seeing the short.
If it's a say 5 amp command station, a 'short' with some resistence that allows 4 amps to flow through the 'shorted' compnents is not a short, the current threhold is below the cutoff of the system.
A realtively high resistence short is quite common if a loco derails and the only thing pressing a wheel against the rail is the weight of the loco, ie, it's not a wheel jammed between a stock rail and the point of a turnout. A resistence of just 4 ohms at 15V to the track is nearly a 4 amp 'short' which wouldn;t trip a 5 amp breaker. In other words, you cna put a 4 ohm resistor across the track of a 5 amp booster and it won;t shut off - but that had better be a big resistor and you better hold it with oven mitts because it will get very hot. I^2 * R : 16 * 4, 64 watts. Certainly capable of melting plastic, let alone fry electronic components made for 1.5 or 2 amps peak.
This is why you need to do the quarter test. And why the woarter test is setting the quater across the rails, NOT pressing down. You need the power to shut off just from a quater sitting on the rails under its own weight. Pressing down makes a better conact between the rail and quartrer, and lowers the resistence of the 'connection'. A derailed loco sitting sideways might not press down on the rail that hard.
Thanks, Guys. I keep learning.
Crandell
I started with the idea that I would disassemble the engine and tender and have a look inside. When I started to disconnect the engine from the tender I noticed one of the six wires between the two had insulation melted including two wires somewhat melted together (this must have been the smoke I noticed) possibly creating a short. I reinsulated the wires with the liquid tape insulating material and everything seems fine. Will check again tomorrow.
Thank you all for your input.