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Dead Spots on 4x8 oval HO DCC

5K views 27 replies 9 participants last post by  robz 
#1 ·
Now for some reason, I have two dead spots. A few nights ago every thing was fine. Now in two spots both locos, a steam and a diesel both stall.
The spots are separated, half way round The layout. Same spot every time. I just added three Caboose thows to the Atlas snap turnouts on the near side of the 8'x4' layout. The stalls are on the outside oval. Most of the track is soldered. I did not solder the turnouts. The stalls are few inches from the feeders.
When a locomotive stalls the digitrax flashes and both locos stop.
 

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#3 ·
I agree with Cycleops. If your Digitrax controller flashes
at the point the locos stop, there is some sort of short,
if only momentary.

You might try the same procedure we use to find why
a derail at certain spots.

Run your loco as slow as it will go to the point where
it stops. You should be able to see what is touching
what that could cause a short. There may be a stray
piece of wire, or metal shaving. The weight of the loco
could cause a slight track movement resulting in
an electrical contact.

If that doesn't uncover the culprit you might try
simply pressing with your hand at the spot of
stop. If that also causes the Digitrax to show short,
there has to be some stray contact.

Don
 
#4 ·
Shorts at turnouts?



robz;

Are your locos stalling while on top of the turnouts? Have you tried temporarily disconnecting one of the Caboose Industries ground throws? Do your ground throws have built-in electrical contacts, and, if so, are the contacts wired to your turnouts? It's possible that a wheel is shorting between two rails where they almost meet at the frog. This usually happens when the frog's plastic is worn down by long use, or sanded down by misguided modelers. If the rails show at the point of a plastic frog, try painting the top of the frog and see if that helps.

Regards;

Traction Fan:smilie_daumenpos:
 
#13 ·
"It's possible that a wheel is shorting between two rails where they almost meet at the frog. "
This what I think is happening on the new box car.

The ground throws are not wired.
The Atlas snap turnouts are about a month old. I do not see any metal at the plastic frog.

Are your locos stalling while on top of the turnouts?
For this issue they are not, occasionally they do stall when backing through for switching. Its annoying but livable.

I am running very slowly the loco with two of the new cars and have not had a stop for about 45 minutes.


robz;

Are your locos stalling while on top of the turnouts? Have you tried temporarily disconnecting one of the Caboose Industries ground throws? Do your ground throws have built-in electrical contacts, and, if so, are the contacts wired to your turnouts? It's possible that a wheel is shorting between two rails where they almost meet at the frog. This usually happens when the frog's plastic is worn down by long use, or sanded down by misguided modelers. If the rails show at the point of a plastic frog, try painting the top of the frog and see if that helps.

Regards;

Traction Fan:smilie_daumenpos:
 
#5 ·
You can make a really nice tester using an alligator clip test wire (cut in two) then use a 1200 ohm resistor in series with a bi-color (usually red-green) two lead LED. It will glow yellow in normal DCC and either red or green on DC. Great for detecting phase problems on DCC track! Use mine a lot.
Saw Steel

You can actually the individual red and green LED's so it easy to see which way the track phase is. I mainly used it when testing the frog power to get the phase right.
 
#14 ·
What is a phase problem? Would that be a bad controller?


You can make a really nice tester using an alligator clip test wire (cut in two) then use a 1200 ohm resistor in series with a bi-color (usually red-green) two lead LED. It will glow yellow in normal DCC and either red or green on DC. Great for detecting phase problems on DCC track! Use mine a lot.
View attachment 295417
You can actually the individual red and green LED's so it easy to see which way the track phase is. I mainly used it when testing the frog power to get the phase right.
 
#6 ·
Lemonhawk's tester got me to thinking.

Stop the locos far away from the stop spots and
let them park but with the track 'hot'.

Use your multimeter set to AC and read the
voltage at the track drops. Then slide them along
toward the stop point and see if there is any kind
of reading change.

Any change means a trouble spot.

If no change do the same but additionally
press on the track as you move to the stop spot.

What happens?

Unless you used the ground throws to change
frogs etc. they should have no effect on the
track. Could you have inadvertently changed
the track drops when you installed the ground throws?

Don
 
#8 ·
Thank you all for your help. I have isolated the problem three new box cars, one in particular is an issue. When ever that car is being pulled, and that car is passing through two particular turnouts, that's when the problem occurs. I bought three Bachman HO silver series 40ft box cars from M.B. Klein. One car was an issue from the start, kept derailing on the curves, one wheel truck seemed a little loose, but the screw was very tight. I took it off and put a sliver of electrical tape around the post and put the wheel truck back on. It seemed to help, no more derailments. Then the stopping issue became apparent. The other two were okay, but now they are occasionally shorting over the other two mainline turnouts, (no ground throws). I moved them up behind the tender and now they seem okay, only a quick flash on the digi controller.
The problem car I am not running, going to find out if I can return it.
Thank you all.
 
#10 ·
It appears that you may have some out of
gauge wheel sets. Sometimes this happens
on a turnout frog with the thin insulator. One
solution is to put a tiny dab of clear finger nail
polish on the rail EITHER side (but not both)
of the insulator. This will prevent the metal
wheels from shorting. Others have used a fine
file on ONE rail.


Don
 
#16 ·
We typically talk about connecting the red output to the right rail and the black to the left rail, but if you have a reverse loop or a switched frog sometimes across an insulated joint the red side meets the black side and when the loc crossed the insulated gap it shorts. Since DCC is an A/C waveform they are out of phase. A reverser quickly detects this phase difference and switches the power to the rails to get it in phase.
 
#18 ·
That should definitely fix the problem -- if it is being caused by the metal wheels momentarily touching BOTH rails at the frog. If the problem persists, then we start over figuring it out.

What kind of turnouts are you using? There are some possible modifications to the turnouts that should eliminate the problem and allow you to keep your metal wheels.
 
#27 · (Edited)
No, it is where the line from the word frog and the v shape meet.
The drawing you posted shows the frog is insulated, which Atlas snap switch is not.
Th frogs rails come to a point near the frog is where you have to look at.

Look at this video and go to the 7:36 mark or could use a file as MtRR75 posted or use nail polish.
 
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