Hello, I am new here and new to model railroading also. I have an engine with a DH123D HO Scale Mobile Decoder. I am currently waiting for my super chief to arrive so I do not have a DCC system to test with. I ran this DCC Engine on a DC track just fine, then I placed it on another track and the engine seemed to not be able to go at full throttle and stuttered a bit. Then the engine stopped and the overload light lit up. I took the engine off the track, investigated the track and engine for debris and found nothing. I place the engine on the track again and gave it throttle and the overload light lit once again. I removed the engine body to look over the wires and everything seemed to be fine. I placed the engine on the track and gave throttle once again to see the overload light lit. I removed the engine once agian and I happened to touch the decoder and it was hot. Other engines seem to run fine on this track with no problem of overloading. I do not have access to another track at the moment so I can not test the DCC engine on another track. I was just wondering if anyone has had experience with this issue and could maybe shed some light on it for me. thanks for any info, Matthew
Sounds like the decoder is wired improperly. If it were on DCC I bet that decoder would have gone up in smoke in a few seconds. What kind of engine is it?
Hi Matthew [#welcome]
Unfortunately it sounds like the decoder has “fried” itself. It will no longer work properly. I wouldn’t suggest any further test runs until the cause has been identified.
This is likely to be for one of the following reasons
- as Joe says the decoder wasn’t installed properly in the first place
- there was a short between the track input and motor feed
- the motor stalled temporarily for a mechanical reason (a slight bind in the mech or hitting an obstruction) and drew too much current, exceeding safe operational limits for the decoder
- it was a duff decoder - I have preiously simply had a bad unit with a DH12* series decoders
When decoders operate beyond the peak current rating for even a very short period of time the micro components generate severe amounts of heat that can damage the components and even melt the solder; in extreme cases it has been know to cause a flash fire (a friend at my club insisted it would be safe to use an HO rated decoder in a small G guage loco despite being warned by anyone who was already operating DCC not to - with smokey results).
Can I ask what DC power pack you used and what loco the decoder was installed in? There are known issues with some locos.
the digitrax decoders are rated at one amp for ho,n and z scale. i put a dz123 in a 40+ year old ho a.c. gilbert hudson a few months ago and it runs fine. i just can’t overload it with too many cars to pull since i don’t know how much current the motor is drawing. if you stall a motor by trying to pull too many cars you may exceed the current rating of the decoder. you have to make sure that a decoder that you put in is able to operate on dcc and dc too. some of them are not dual mode decoders
Thanks for the reply. Let me include a few more details. The loco is a F2 Loco - 8 Wheel Drive Pick Up from model power. #6806 AMTRAK The DC power pack that the overload occurred on is an Athearn that was included with a Coca-Cola Train set. I had the decoder installed by a professional and it was tested at his shop and appeared to be working great. I then took it over to a friend’s house to test on a DC track and it worked fine, speed was great, however there was no reverse on the Loco. I just figured that due to the DCC decoder being installed, the reverse was disabled in DC mode. I am new to this, not knowing all the details of the hobby. After testing the Loco on the DC track I brought it home to run on a segment of track that I had. This is when it started to stutter and then stop all together. I have removed the blue plastic cover to inspect the circuit board on the decoder. There appears to be no heat damage to any chip or solder points. I am patiently waiting for the arrival of my DCC system to test the decoder on it. thanks for all the info and help, and I am looking forward to being an involved member here at trains.com. thanks, Matthew
I’m going to vote for improper installation or possibly blown decoder. If your installer left it set for automatic DC conversion, it should have run in both directions just fine on DC, as if the decoder wasn’t even there (although maybe slightly less than the old DC top speed - not a LOT slower, just a tiny bit), and perhaps the lights wouldn’t be on. But the fact that it didn’t run in reverse was already a warning sign. If the decoder was NOT set for DC conversion, it wouldn;t have moved in either direction on DC, it would have just sat there.
–Randy
I have to agree with Randy’s assesment. I also have to add that even though you can run (most) decoder-equipped locos on DC, and vice versa, it’s not the preferred method. Doing so opens the door to the possibility of all kinds of Bad Things, ranging from nothing more than poor performance to melted loco shells and blown decoders. Unfortunately, you may already have found that out the hard way…
Steve
yah… just what was weird is that it ran fine a few hours before or at least seemed to. =( I dont think i can go back to this guy that put it in and tell him its broke, it worked when I left. Maybe I can just by another decoder from him. I cant seem to find this decoder in any hobbyshop. thanks Matthew
It sounds like improper installation or programming, in either case not your fault so dont feel bad. If it only ran in one direction I think that the dual mode capability must have been either turned off or this is not a dual mode decoder. Only running in one direction seems to me that the decoder was treating the track power as if it were AC, like it would be on a DCC powered layout. So it sounds like you need a new decoder. I would suggest a TCS T1 www.tcsdcc.com and install it yourself. If you botch the installation or have more problems resulting in the destruction of the decoder, TCS’s warranty has a no questions asked free replacement policy.
Good luck.
ok thanks for the tip
The DH123D definitely can handle analog conversion.
While running a non-decoder loco on DCC can cause the motor to overheat if left standing too long, doing the opposite, running a decoder-equipped loco on DC, poses no danger to anything unless you are powering your HO layout with a large scale power pack putting out over 20 volts. About the only exceptions are the Soundtraxx DSD and DSX sound decoders. Pretty much every current DCC decoder supports analog conversion to allow the loco to be used on DC track without removing the decoder. All that really happens internally is the decoder, when not seeing a DCC signal, closes the motor drive transistors and allows track voltage to flow directly to the motor, minus the junction drop of said transistors (hence top speed will be SLIGHTLY reduced - about 1.2 volt’s worth, not much at all).
Bottom line, the specified decoder should work fine on both DC and DCC, if installed and set up correctly.
–Randy
well, i got the instructions for this decoder and the wiring was done correctly. I guess it was a defective decoder. Since its allready wired for this deocder, does anyone know where I can order one for under 20 bucks? Thanks for all the help. Matthew
OK, well the TCS T1 will plug right into the 9 pin harness that was installed for the DH123. Again if it is the wiring that is the problem TCS will replace it free if something unfortunant should happen[}:)]. www.tonystrains.com has lots of discounted DCC products, I think they charge about $15 for a T1.
Have you tried contacting the manufacturer of the decoder and discussed the issue with them? They might just replace it for you.
Just my [2c]
I stand by all my old opinions on this one. If you wanna run DC, run DC. If you wanna run DCC, run DCC. It’s really not that tough.
I recommend contacting Digitrax; they will probably replace your decoder for you for no charge if it is under warranty.
Be careful with using DCC decoders on DC. I would measure the maximum voltage from the power pack with a 14V 100 to 200 milliamp lamp across the terminals. Or you can use a 100 Ohm 3-5 watt resistor instead (caution it will get hot). Some power packs will produce an output greater than 14 V DC, despite the value stated on them.
Also clean track and wheels are helpful with DC; abrupt breaks in current at or near maximum voltage can cause decoder damage. I witnessed this situation early in my DCC experience. DH123D’s were the decoders that failed in my case.
Until you receive your DCC system, I recommend limiting the speed of you DCC equipped locos to mid or 3/4 speed.
Happy Railroading !