Any tips to troubleshoot TCS CN-GP short circuit

[bc6]

I installed a CN-GP in my Atlas SD9 and when I turn on my programming track I get a short circuit detected. Ive installed the boards per the manual and soldered per the manual and nada. I will go and re-read the manual in order to make sure I havent missed anything.

[jagged ben]

Did you carve out a channel in the motor mount for the wires to pass through?  See the picture in the middle of pg 5 of the installation guide.
http://www.tcsdcc.com/public_html/Customer_Content/Technical_Info/Tech_Manuals/TCS_Book_of_Classic_N_Installations.pdf
Not doing this step is probably the most likely to result in a pinched wire and a short.

Another possibility is that the motor brush caps or contacts are touching the frame, if you built up too much solder on them or got them oriented badly.   Kapton tape along the inside of the frame can be very helpful here.

And another possibility is you may need to mill away some of the frame to make sure that none of the decoder components are touching it. 

[bc6]

Hey jagged thanks for the suggestions I'll see if I can remedy my problem with your advice.

[johnhale]

I have installed a dozen of these and each and every short on the programming track is related to no isolating the motor properly. As Ben pointed out, Kapton tape is the savior. I use it over the motor brush caps (making sure there is a small hole in the it to correspond with the hole in the cap - it is there for a reason) and to keep the wires in place on the side of the motor.

John

[Burlington Bob]

I just installed a CN-GP in a LifeLike GP20 and was sweating bullets that I might get a short or ruin the motor from soldering the wires to the brush caps but everything worked out OK!  I was wondering though, if I did short a wire from being pinched what are the chances of ruining my decoder?  Or would it most likely be a case of it not working until the short was corrected?  I was kind of stoked after my success with the CN-GP as the only installs I had done prior were just drop in replacement boards.  Now, I'm thinking of more projects along the lines of adding MARS lights to my Kato F3's.

[wm3798]

I've done a scad of these, too, and I've found that at times, the TCS quality control department is me.  By process of elimination, I've discovered shorts in the small back board, in the lighting circuits, and once in a while, in the installation (i.e. my fault!)  But every time I've sent one back, they've been courteous with the warranty replacements.

Lee

[bc6]

One thing I forgot to add is that the brushes in one end of the motor was broken in two pieces, Would the broken brushes affect the operation of the motor.

[peteski]

There are supposed to be  two brushes. Or do you mean that one brush was broken into two pieces?  If it is the latter then depending on how it was broken, it can affect the motor's operation.  I suppose that it can even jam the commutator.  If there is a larger ans smaller piece,  try just installing the larger piece. But you would be better off just replacing it with a new unbroken brush.

[bc6]

There are supposed to be  two brushes. Or do you mean that one brush was broken into two pieces?  If it is the latter then depending on how it was broken, it can affect the motor's operation.  I suppose that it can even jam the commutator.  If there is a larger ans smaller piece,  try just installing the larger piece. But you would be better off just replacing it with a new unbroken brush.

Thanks Peteski I meant that one of the brushes were broke into two pieces.

[M.C. Fujiwara]

This EXACT issue just happened to me: good thing I read this thread before starting another.
Installed in Atlas GP-7, followed directions, isolated motor (well, wrapped it in tape, yes?), wires fit down past plastic motor frame fine.
Put on Programming Track: "Cannot read CV"



I'll go back and check to see if any part of the motor is touching the frame, but is there anyway to check if the decoder is bad?
I have no fancy thingamabobs, just my NCE PowerCab and a multimeter.

[M.C. Fujiwara]

Motor seems isolated fine.

When I hook up the multimeter and touch one decoder tab (RED), the meter shows no current through grey, black or orange.
However, when I touch the other tab (YELLOW) and those three wire solder points, the needle moves a wee bit.



Does this indicate something fried, miswired or normal ?

[M.C. Fujiwara]

When I touch the multimeter to the orange and grey solder points on the decoder itself it shows current between them.
Is that normal?

[peteski]

MC,
your description is a bit vague.   I assume that you are measuring resistance (not current). Well, the meter passes current throuigh the circuit, but you  usually don't mention that part when you are actually trying to measure resistance. 

Assuming that your multimeter is in fact in the ohm range, you should specifiy what resistance values are displayed on the meter (rather than "no current" or "some current").

If there is no continuity (open circuit or very high resistance) between red and black (or the chassis halves) and orange and gray (in any combination) then that is a good sign (but this in itself doesn't guarantee a good decoder either).

If the motor is in the gray/orange circuit (as in your example) then if you measure resistance between gray and orange (in a good decoder), you'll actually be measuring the resistance of the motor. That should be fairly low (less than 100 ohms but not less than lets say 5 ohms).

I think that so far there is nothing concrete indicating a bad decoder.  I'm not really familiar with this specific decoder so I'm being a bit vague myself.

I woudl try to reassemble the loco chassis and put it on the programming track. Then as you go into programming mode, observe the motor and headlight LEDs. Normally when the DCC system tries to identify the decoder, the motor armature will twitch and/or the headlights shoudl flicker a bit.  DO you see any of that happening? 

Another quick test (assuming that by default the TCS decoders have the DC mode operation enabled) is to take a 9V battery and place it across the wheels (or across the chassis). The 9V battery terminal spacing is perfect for doing that, and 9 volts is plenty to get the motor running.  Does the motor run when the loco is powered by a 9V battery?

[M.C. Fujiwara]

Thanks, Peteski, for taking the time write that all out, even will all my vagueness 
After messing around with it, it seems that there was a conductivity issue with the decoder tabs that "plug" into the frame.
When I pushed down on the decoder the programming track could read it & run it.
Unfortunetly pushing down on it also broke the tabs 
Luckily TCS has a "no questions asked" 1-year exchange policy, so I'll do better with the "new" one when it shows up in the mail.
Cheers!

[johnhale]

I have had this problem with different drop in decoders in the past. After reading a suggestion online, I "add" a little thickness to the contact points on the TCS decoders by adding a little solder on each one. That makes it thicker and it fits snug in the frame slots. You can bend the frame down also, but I have had mixed results with that working long term.

John