Digitrax

[Ken G Price]

wtierce
Thank you for coming back with updates as I was interested in your Digitrax decoder problem. I use them in 9 of my 11 engines.
So many original posters never do reply the the responses.

[Doneldon]

wtierce-

Remind your friend that he can hang on to the original motor and any other gear so it can always be restored to OEM condition. This would be important if the loco turns out to have some collector value. I have no idea of the chances of that, but he might feel better about an upgrade/update if he knows he can always go back to nature.
                                                                                                                                                                                                                               -- D

[Jim Banner]

...  I still don't understand the thing about my engine. It is relatively new.

There are all kinds of possibilities.  Perhaps a previous owner used steel wool to clean the rails.  Motor magnets love this stuff and will suck it into a motor faster than you can blink an eye.  Sometimes a bit of iron, for example a coupler screw, will end up in the locomotive and short from frame to motor or a bit of bare wire or solder will do the same thing.  These or anything else that cause an inadvertent connection between a rail connection and a motor connection will blow a decoder.  At least you haven't had the problem one young fellow had - he blew five decoders before he finally gave us a detailed, step-by-step list of exactly what he did to install them.  He was putting them into an Athearn's locomotive, one of the ones with a flat springy metal strap that connects the top motor brush to the front and rear truck and to the headlight.  Turned out he was putting that strap back in place each time he installed a decoder, not realizing it connected the orange decoder output wire that went to the top motor brush to the red decoder input wire that connected to the right hand wheels.  He thought he had the motor isolated because be had put tape under it.  But he forgot that an input to output decoder connection is an non-isolated motor, no matter how or where the connection is made.  And an input to output connection on a decoder will blow the decoder every time.  There are many ways of getting an unwanted connection.  For example, getting a decoder wire caught between a locomotive shell and part of the frame.  It may work for years until one day the insulation gets squashed or worn off and the wire conductor touches the frame.  If it is the right wire, good bye decoder.  When is this accidental contact most likely to happen?  When you pick up the locomotive, such as to put it on a programming track.  I don't say this IS what happened to your locomotive.  Just an example of what CAN happen.

I hope this experience will not turn you off DCC.  I hope you can look at it as a learning experience, just like your friend's locomotive.  From that you learned the importance of measuring motor current BEFORE you select a decoder.  Whether we like to admit it or not, that is a lesson most of us have learned, and mostly we learned it the same way.  It is just a little easier to accept if it is the tenth decoder you install that burns up rather than the first.

Jim

[WTierce1]

I didn't get the train from another person, I got it brand new for Christmas a few years ago. Also, Sly knows that he can keep the motor.

[Sierra03]

NCE makes some decent decoders and they are reasonably priced and they provide alot of info about them that digitrax dosen't. i haven't had any problems with them yet

[jward]

i have a question about the nce decoders. i believe the ones i have are d13sr. do these support switching speed the way digitrax does? on the digitrax decoders you can use function 6 to cut the locomotive speed in half for yard work (or to slow down your kid's locomotive)........

[Sierra03]

Like Digitrax decoders you can program the max speed  via cv6 on your program track to limit the max voltage that goes to the motor to keep the locomotive from running at top speed. If cv6 is programmed as 0 the the max speed is defaulted at 255 which is full motor voltage for max speed. any value less then 255 lowers the max speed of the locomotive.  128 would program it to be about half speed for the maximum and anything lower would be less max speed.  65 would be about 1/4 for the max and 192 would be equal to about 3/4 for the max. 

[Sierra03]

sorry that was cv5 for the max speed - you should set cv6 for half of what cv5 is because that is your mid speed which means you get smaller increases in motor speed through the lower ranges rather than taking off like a rocket to the setting of cv5 as you increase the throttle setting- more protoypical rather than "stomping on the gas" so to speed as you accelerate from a dead stop.

[Sierra03]

Sorry I failed to answer your question. I am not sure that they use the F6 or not to set switching speed. I just have programmed certain locomotives for full time switching duty speeds and use them exclusively in that role. I will have to find out if that can be done. But for a child's locomotive to keep the speed from being at max all the time i would just reprogram it for a lower top speed.

[flrailroads]

I installed a DN135D decoder in a new HO Bachmann Spectrum GE 44 Ton Switch Engine.  Decoder wires are soldered to terminals on the engine's pc board (H800X-PCB01) per parts drawing.  At slow speeds (8-12 on Digitrax DT402 throttle) it operates fine.  However at speeds above 15 (a moderate switcher speed)  the decoder looses control, i.e. it won't slow down, stop or reverse unless I lift loco off the track.  Then I can restart it.   The decoder is only connected to the motor, not the headlamps.

I am suspicious that several components on the Backmann loco's pc board may be the cause.  There are two 1µF ceramic disk capacitors and two small wirewound chokes.  There were no instructions accompanying the locomotive recommending disconnecting either the caps or chokes if wiring for DCC.  Has anyone had a similar experience with this or other Bachmann locomotives & Digitrax decoders?

[Jim Banner]

  Has anyone had a similar experience with this or other Bachmann locomotives & Digitrax decoders?

Control problems with silent decoders are often caused by those capacitors you saw.  Cut them out or clip just one lead and swing them out of the way if you want to keep them handy.

Jim

[Sierra03]

Jeffery,

I did some more research and as far as I can tell about NCE decoders is that they don't have the reduced speed switching mode that digitrax does. I don't have access to check it out as my locomotives are on a railroad museum layout so I will have to check it out next time I am there and see if they do. However from what I can tell from my literature I have on hand I think its safe to say no they don't.  As i said you can just reprogram the appropriate cv's (5 & 6) for the desired speed for switching for true full time switchers if you have units you can and are willing just to dedicate to that end- full time switchers that is, otherwise for road locomotives or road switchers that would be a pain having to reprogram just for switching service and then have to reprogram again to go back to just mainline service only. But I am curious about it now and perhaps that is a suggestion that should be made to NCE about future decoder models or revisions to their existing line of decoders.

[jward]

that's what i was afraid of. i think it's cv57 that you have to set. the nice thing about this is that you can have your switchers set to run at this speed permanently, and the road power set to use switching speed in the yard, or when there is a switcher in the consist. real life switchers were often restricted to 40 mph due to their trucks anyway, and this would be an interesting wrinkle in operating the layout.

[Sierra03]

57 or 54,  one of those 2. It says in the DS13sr decoder literature that some cv's including those in the 50's can be programmed but will be ignored so that would preclude the instant selection of switching speed mode. So you would have to stick with Digitrax decoders for that luxury of instant change to the switching speed mode.

Yes, most switchers were capable of faster speeds depending on the gear ratio applied - the lowest gearing on EMD units allowed 55 MPH  but due to those hard riding AAR type A switcher trucks underneath the units most switchers were limited to 35 mph. You could go faster but you probably would have been shaken to death in doing so. If the switcher is a working trailing unit in consist with no crew on board a higher  speed would be ok because the crew wouldn't get rattled around. You would just have to watch the max speed so the unit wasn't  overloaded and burned up something in the somewhat primitive electrical systems, or the components thereof, of the time when they actually built units just as pure switchers for yard or light road service switching capability.  If just towed along in consist idling and isolated or dead in tow then it wouldn't be an issue as to how fast it went other than it may shake something loose on the unit from vibration.

Interestingly and oddly enough- NC&StL and Alaska RR had GP7's , and perhaps other roads and/or other models,  that were factory equipped  riding on AAR type A switching trucks. I  think that  eventually they were probably changed out for the normal Blomberg road truck after enough crew complained about the rough ride or they found out it was hard to use them at other than lower road speeds- it would be akin to driving your vehicle with the shocks taken out.

[flrailroads]

ref: Reply #24

Thanks to Jim Banner's reply (#25) I disconnected the two 1µfd ceramics on loco's pc board and the decoder now remains in control of loco