I bought an old HO F7A at a train show. I have a DCC layout, but this (Athearn?) has no decoder. It only runs in one direction.
How can this be? It's simply 2 trucks and commutator brushes.
What can be wrong?
Terry
Something is binding in reverse ? Just pulling at straws with what little information is provided ....
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Have you opened it up to verify that is is a simple old BB Athearn and has not been modified in any way?
How are you test running it? A 9V battery works if you have no DC power pack.
--Randy
Modeling the Reading Railroad in the 1950's
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TBat55 I bought an old HO F7A at a train show. I have a DCC layout, but this (Athearn?) has no decoder. It only runs in one direction. How can this be? It's simply 2 trucks and commutator brushes. What can be wrong?
You have a DCC layout and tries to run a non DCC equipped locomotive?
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Well, my Digitrax system can run a non-decoder loco in both directions....
Only way it would go only one way is if it had some sort of diode system installed for some reason. There is an old trick to run 2 DC locos on the same track under independent control, using a diode in each loco (installed opposite ways) and one loco is controlled by the top half of an AC power source and the other is controlled by the bottom half. Problem is, neither one can reverse.
Mark R. Something is binding in reverse ? Just pulling at straws with what little information is provided .... Mark.
For those who missed it, DC only, no decoder.
We have to assume you have a DCC system that can run a DC only loco. Gears might be locked up in the other direction. Remove the shell and do a visual.
Sure need more info.
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.
richg1998 Mark R. Something is binding in reverse ? Just pulling at straws with what little information is provided .... Mark. For those who missed it, DC only, no decoder. We have to assume you have a DCC system that can run a DC only loco. Gears might be locked up in the other direction. Remove the shell and do a visual. Sure need more info. Rich
I assume that the DCC system could be not DC capable, as what might happen when a DC loco is placed on a DCC layout could be running in one direction (running in the most generous meaning, as it is more rushing loudly...).
However, if it is doing that it shouldn;t be under any control, and if it IS doing that, the DCC system is out of whack as this means the waveform is not totally symmetrical, to give a bit of DC potential.
I have only used the NCE power cab and a NCE 5 amp power pro. They cannot tun a DC only loco. All the loco motor does is buzz.
Hope the OP gets back to us. Kind of strange so far.
I agree with finding a way to test it on DC. I know some DCC systems have a way to run a DC engine (I think in Digitrax the ID no. is either 00 or 01?) but as I recall it usually doesn't work very well. Since DCC uses AC, it might be it's just not reversing polarity to change direction the way a DC engine requires.
Some motors work better than others - the loosely assembled Athearn BB motors, the gold ones) buzz loudly because the only thing holding the whole motor together are the top and mottom clips, and the magnets aren't even glued to the case.
It works by lengthening the 0 bit in the DCC waveform since the spec says that any peak under a certain limit is a 1 bt and anything longer than a certain value is a 0 bit. There's a lower limit on the 1 bit (have to have SOME pulse duration), but there's no real upper limit on the 0 other than the rest of the specs and the need to transmist a certain number of commands. So you make either the positive half of the 0 bits longer, or the negative half, and this gets you a net DC potential across the rails while still sending the 1's and 0's of the DCC command bitstream. Connect a DC meter to the rails arbitrarily and one way you get a positive DC voltage and the other way you get a negative. So a DC motor will turn one way or the other.
That's what makes this strange - or else indicated this loco has additional circuitry inside other than a simple BB loco. It's not going to only turn one direction, assuming a DCC system that indeed supports running a DC loco.. If it sits and buzzes, that's normal for a system that cannot run a DC loco. If it goes one direction on a DCC system that does NOT support a DC loco, then the DCC system is putting out a non-symmetrical waveform which shows up as some DC potential, but the loco would just move by itself, not be under any control.
wjstix I agree with finding a way to test it on DC. I know some DCC systems have a way to run a DC engine (I think in Digitrax the ID no. is either 00 or 01?) but as I recall it usually doesn't work very well. Since DCC uses AC, it might be it's just not reversing polarity to change direction the way a DC engine requires.
They have been around since the beginning of DCC. I had the MRC2K at one time.
1) WHAT DCC SYSTEM SUPPORT DC/ANALOG OPERATION
All Digitrax All LenzAll EasyDCCBachmann's EZDCC MRC's long discontinued Command 2000 and Prodigy
TBat55It only runs in one direction.
Is the "one direction" relative to the locomotive or the track. If it is relative to the locomotive, then it is obviously something with the locomotive causing the problem (gear binding, wiring oddity). If it is relative to the track, there is another possibility, though I would expect you to notice the problem from other symptons. It could be that one side of the H-bridge in you DCC booster/command station is blown.
Early NCE/Wangrow also did zero stretching for analog operation, but you had to build a 'throttle' for it yourself and connect to the serial port on the command station.
Sorry I could not get back to my posting. Medical emergency.
I've run other DC locos on my Digitrax layout (with address 03). But this one ... I'm looking for a diode like Randy suggested, but took the motor out of the frame and reassembled it (nothing in the wrong way, diode would have to be in the trucks). I'll try a plain old DC transformer over the holiday but it should not matter. Thanks for replies. I'll update if root cause is found...
and "it only runs in one direction means" if it's going to the right and you turn it 180 degrees it will go to the left. No speed control, full speed only. Reversing from the command station does nothing. I put another DC-only loco (no decoder) at address 03 and it worked fine. Wiring is fine (not an electronics expert but know a little more than most).
This is driving me nuts.
On my Digitrax system, DC locos run on address 00... 03 is the default address for a decoder.
Simon
No idea how you are running a DC engine on a DCC system on address 03. (?)
This may be your problem. Digitrax uses Address 00 to run a DC loco. So if you are dialing up address 03, no wonder you have no control. And at some point, when you last used address 00, you left it set on a high speed in one direction and did not set it to stop and dispatch it, so the system is constantly running address 00 at a high speed, so as soon as you set this loco on the rails, it will take off, in one direction, and not change since you are trying to stop and/or reverse it using address 03.
DCC decoders fresh out of the package default to address 03.
My bad. The loco I have that I thought was DC actually has a decoder inside of it (address 03, never looked inside) so I thought 03 was for DC. All the rest have decoders set to cab#. Don't remember ever using address 00, or how it is set, but that must be my problem.
I am officially a recovering idiot.
TBat55I am officially a recovering idiot.
I think today turkey would be more appropriate.