Yes, another DCC decoder question...

[Anonymous]

I recently installed a Digitrax decoder in a Proto 2000 E6, (the correct decoder according to the manufacture's list) and the locomotive has developed all sorts of strange behavior -- running away unexpectedly, stopping for no apparent reason. Once, when I hit the light button, it stopped dead in its tracks.

I tried reprogramming the decoder, and is said "CV not recognized." (I have an NCE PowerCab that works fine on all my other locomotives.

I removed the body shell, the the bare chassis of the E6 ran fine.

Question: Is is possible that the motor or electronics of the locomotive is causing interference that 's causing the locomotive's bi-polar behavior?

Thanks much in advance...

[simon1966]

If I understand this correctly, the loco runs fine without the shell on, but not with it installed? Do all the lighting effects work correctly when the shell is off?

I would check your installation and see if there are any wires that are shorting when the shell is installed.

[cmarchan]

Question,

Are you using a decoder with the 8-pin plug attached to the original PC board? If so, examine the board carefully; look for small beads of solder or loose wires. Also check to see if the leads of nearby components are touching each other. BTW which decoder are you using?

Carl

[Anonymous]

Thanks guys,

Yes, the lighing effects work with the shell off. And yes, it's an 8-pin plug attached to the original board. There are no loose wires or leads. Sorry, I don't have the decoder # here with me. It has the basic 8 wires, along with 2 extra wires (unused)....

[simon1966]

Very strange. I can not think of any reason for a decoder to behave without a shell installed and not with the shell installed other than an issue with wiring and or the plug into which the decoder is installed. Are the extra wires fully isolated and taped off?

[Bre2tSco2t]

What kind of clearances do you have in the shell? If the shell is pushing on the decoder, or board then a minor defect may service only when there is pressure. Once the pressure is removed, you can't see it or locate it..

Or the pressure could be making things touch that shouldn't be touching.

Strange problems like these require you to ask strange questions.

Good luck, and let us know if you figure it out. That could help us if we ever have the same behavior.

[Bre2tSco2t]

Wait, you said Proto 2000.

http://www.nmra.org.au/Hints/P2K/P2K.html

Could this be your problem? You just think its fixed with the shell off?

[Anonymous]

Thanks for the link. Although this E6 loco has 6 wheel trucks, I'll check to see if it's something similar.

To your other question: there is VERY little clearance in the shell. I suppose I will have to use Aggie engineering (otherwise known as trial and error) until I find a way to keep the decoder isolated from the other electonic gadgets....

[simon1966]

Here is a good picture of an E6 installation using a long harness from TCS to get the decoder out of the way of the circuit board.

If you have the decoder plugged directly into the NMRA plug there does not look like there is enough room on top of the transitors on the main board. Anyway, perhaps this will give you an idea to solve the problem.

http://www.tcsdcc.com/decoderpics/lle6.html

[mtrails]

Decoders are sensitive to magnetic interference, which leads me to beleive, the location of the decoder itself, in realation to the motor is the reason for the erradic behavior. The decoder should be placed directly over the motor. If this is not possible, the decoder must be placed as far toward the end of the shell (whichever end of the body that has more room).

If you have abundant wires within the shell that need to collapse onto one-another to fit within, the decoder may be subject to electro-magnetic interference, as a result of current passing over it more than one instance. This may explain the lighting effects working with the shell off. I had an instance of the "constant light" flickering, until I trimmed the lead wires to the bulbs, to equal length. I will also add, that wires running straight, vs. bending, twisting, and looping will greatly reduce elctro-magnetic interference.

[Anonymous]

Thanks much guys! Great info! I'll follow all your suggestions and report back on the results...

[Anonymous]

I still haven't solved the problem, but I've narrowed it down a little. Last night I ran the loco with the shell off and it would run forward ok, including with the light on. But in reverse it was another story. It ran very slowly, then wouldn't stop when I turned down the throttle.

Also, if I pushed the 8-pin decoder a little, it would start running normally...sort of. Soooo, it looks like I either have a defective male or female 8-pin connector.

By the way, the decoder is a Digitrax 163. Has anyone had similar problems with it?

Thanks much

[Bre2tSco2t]

I haven't use a Digitrax 163. I do have and use a Loy's Toys Decoder tester. Can you plug that decoder in another Loco and see if it is the decoder? It may be the board you are plugging into.

[BRVRR]

I use DH163 decoders in several of my locos. I've never run into your exact problem problem, but I had a 'drop' in DH163 decoder that fit so tightly under the shell, coincidently in a PK2 S3, that when everything was in place, the lights acted weird or didn't work at all. In desperation, I removed the circuit board and plug and hard wired a decoder in place. I had to change the light bulbs, but everything works now.

[jeffrey-wimberly]

QUOTE: If you have abundant wires within the shell that need to collapse onto one-another to fit within, the decoder may be subject to electro-magnetic interference, as a result of current passing over it more than one instance.

It sounds to me as if that's the problem. I don't use DCC yet, but I do build computers as one of my hobbies. In fact I built the one I'm using right now. For that reason, I know electro-magnetic fields can wreak havoc on electronics.

[cmarchan]

aspenexile,

Your latest report suggests a broken or cracked soldered connection on the locomotive PC board. I suggest removing the mounting screws ( including the one for the voltage regulator mounted to the frame) and turn the board over. Look for cracked solder joints or just resolder all the joints of the 8-pin connector on the board. Also make sure all the push on connections are secure. Some of them have more than one wire. These connections have been problematic in some E units. You can remove the plastic connectors from the board and solder the wires to make a more reliable connection.