Bachman Venture cars shorting

[milw156]

I picked up a few of the new Bachman Venture cars to run with the Amtrak Midwest Chargers I have, and after putting a few coats of Tamiya smoke over the LED's to tone down the thermonuclear glow, the cars are causing intermittent short circuits. The PSSX2 starts blinking blue, then goes to red and everything shuts down. The cars have some capacitance built into them, and at first, I thought that might explain the blue as the cap charges. if the cars are sitting, all lights are green, but as they begin moving, blue starts blinking, and then red. Anyone else experience anything like this? Short term, I think I will just disconnect the LED strip from the wires to the trucks, but for the cost of these cars, I don't think I should have to do that
Thanx,
Rick

[nkalanaga]

What kind of pick-up do these cars have?  If it's solid metal axles with insulated wheels, I've had two causes for intermittent shorts while moving:

1:  If wheelsets are insulated on only one side, a set may be installed backwards.  Make sure all of the wheelsets in a truck are insulated on the same side.

2:  A wheelset with no insulation.  I've had this on replacement freight wheels.  Very hard to find, in a train, as there are no lights in the cars. 

If the wheelsets are the stub-axle design, with a plastic center and solid metal wheels/axle ends, about the only thing I can think of is the wheels rubbing on a metal underframe, or a short between the two sides of the truck.

It could be something inside the car, but I doubt it, as that should cause problems anytime the car's lights are on, moving or standing.

[milw156]

The wheels are the stubs with plastic center sleeves. Underframe is all plastic, although the coupler has a "funky" wishbone thing on it to provide swing on curves. As a test, I unsoldered both sets of feeders on the left side of the car, and used Kapton to keep the loose ends from wandering, and behold, no shorts. Either there is something wonky in the light board, or the Tamiya smoke paint is conducting between the + and - of the LED's I painted over. At least for now I have a (rather unsatisfactory) solution to the problem. Might have to get another one to see if this issue exists in the unaltered state.

[nkalanaga]

It could be the paint, but I doubt it.  I've never heard of Tamiya paint being conductive.  You're probably right about the light board.

[peteski]

Are all the cars having this problem, or just one?  If they have a keep-alive circuit in them, the circuit might not be properly designed and when the cap charges it causes brief high current spike?  How long do the lights stay on after the fully charged car is lifted off the track?

If I had the light board on hand I could take a look to figure things out, and also how to adjust the brightness, but I ain't buying one of them for the price they go for. 

EDIT:  I can pretty much guarantee that the paint is not conductive.  Even if it was, the LED circuit current is likely  limited by a resistor. Even if the LED terminals were shorted the resistor in the circuit would limit the current (it would not be a "dead short").

[WP Lives]

Don't know if this helps but I have 4 of them and have run them for about an hour on a DC layout with no problem.

[milw156]

Are all the cars having this problem, or just one?  If they have a keep-alive circuit in them, the circuit might not be properly designed and when the cap charges it causes brief high current spike?  How long do the lights stay on after the fully charged car is lifted off the track?

If I had the light board on hand I could take a look to figure things out, and also how to adjust the brightness, but I ain't buying one of them for the price they go for. 

EDIT:  I can pretty much guarantee that the paint is not conductive.  Even if it was, the LED circuit current is likely  limited by a resistor. Even if the LED terminals were shorted the resistor in the circuit would limit the current (it would not be a "dead short").

All 3 of them exhibit the same behavior. Set them on the track and they are fine. once they start rolling, or even rocking the body side to side, then the blue lights start blinking on the PSSX2. eventually the red light comes on and power is cut.
The capacitance seems minor, less than 1 second maybe, I'd have to reconnect the wires and check. I can send you a board, but I need to take a good picture and label all of the wire connections, so I know how to put it back together! In addition to the R&L track wires on each end, there is a switch to turn on /off the markers on each end, for a total of 7 solder joints per board.

[milw156]

The two cars on the ends are as delivered, the one in the middle has been modified by adding Tamiya Smoke paint, 3 applications, to the LED's



With lights off, and all 3 cars having received the treatment


As I was running the train back towards my yard, I noticed the corridor lights flickering, and then going out altogether. I could not see the PSSX2 lights from where I was. The really odd thing about that is that you can pick the locomotive up off the track, and it keeps going for 3 to 5 seconds. My first thought was the speaker magnet picked up a track nail or something. I was nowhere near a turnout, when it happened. Took everything off track, and then put the loco back on and ran it back and forth where I could watch the lights. one at a time, I put each car back on and rolled it down a 7-foot-long straight track with no turnouts and witched the blue lights blink a number of times until the red PSSX2 light came on and power was cut.

[peteski]

If all the cars exhibit this issue on your DCC system while someone else mentioned they seem to be fine on DC layout I suspect that PSSX2 might be very sensitive to short current spikes.  I'm not familiar with it - I suspect it is either DCC breaker or booster.

Edit: Did you mean PSXX-2 not PSSX2?  If yes, that is a "standard" Tony's Trains circuit breaker.  What did you set the trip current to?

How about if you just try running a single car (leave the other ones off the track) does the breaker still reacts?

Yes, if you sent the board to me I can take look at it.  Photos of the wiring will be useful for reassembly, but since you also have other identical cars, you can just look at their wiring.

I'll PM you my mailing address.

[milw156]

So does that appear to be a cap? If so, it does nothing as these flicker as bad as Katos. The cars are about 10gm under weight, but even adding 2x 1/4oz weight (~15gm) did not help much. Fortunately there is lots of room for additional capacitance & weight.
I hadn't considered the trip current, it is as supplied, I believe 2 amps.

[peteski]

That 47µF cap has a minuscule capacitance - should not cause any current spikes high enough to trigger a DCC circuit breaker. As noted, it also will not provide any sort of keep-alive functionality.  It is more to just smooth out the rectified DCC voltage.

As far as Kato (and any other similar passenger car) flicker goes, if you keep the wheels ant track clean, there will be no (or very little) flicker, even with no capacitors.

Kato flicker is a constant complaint at my NTRAK club. When I take those flickering cars and clean the wheels - poof - the flicker is gone. Peopla are so surprised that I can instantly eliminate the flicker.  Just just have to be diligent keeping things clean..

[milw156]

Took @peteski's suggestion and took wheels out of trucks, cleaned out the pickup cups and wheel tread with 70% IPA and result is flickering is almost nonexistent. Thanx for that suggestion, as I would not have considered it with the cars being essentially brand new. I clean the rails with a piece of HO cork roadbed which usually works pretty well, at least for the sound equipped engines. Due to the light weight of the cars, maybe they are more sensitive??? 
I ran the two locos and the 2 cars still with the lighting reactivated in back and forth over about 30' of layout several times with only an occasional and brief blink of the blue LED indicating that the board sensed the need to limit current. took the following video showing how the rocking the car side to side caused the blue LED to blink. I could not get this to happen to a Rapido Horizon car with lights

/>
I am going to guess component B1 is a bridge rectifier??? To add a capacitor/resistor/diode along the lines of what you recommended for the Kato light circuits, is this where it would be wired in? If I'm going to have lights in cars, I absolutely want no flickering AT ALL. It looks better with no lighting at all rather than flickering.  It also means I have to populate it with passengers, although that is an artistic issue, not an electronics issue!

I had taken a board out to send you, but should we bother at this point?

[peteski]

I'm glad the cleaning did the trick. I suspected it would make a  difference. New out of the factory models often have oily preservative covering metal parts (like wheels).  Since you like running lit passenger cars I could build a simple wheel cleaning station to make the cleaning easier.



I use this contraption to do wet wheel cleaning (the paper towel is moistened with 99% Isopropyl alcohol, but denatured alcohol should work too). It also works well for rolling stock with plastic or metal wheels.



If there is a lot of crud on the treads I take the MINITRIX brush and hold a piece of rolling stock upside down in one hand and  with the other hand I run the brush over the wheels applying gently pressure. The bristles rotate the wheels while scraping the treads . Next I place the car in the track with the moist towel and again push back and forth it over the towel area.  For plastic wheels I skip the brush treatment.

That circuit breaker must be really sensitive if it flashes the blue light. I looked at the manual but it is not clearly explained exactly when it is supposed to light up (like what percentage of the trip current triggers it).

[Point353]

Took @peteski's suggestion and took wheels out of trucks, cleaned out the pickup cups and wheel tread with 70% IPA and result is flickering is almost nonexistent. Thanx for that suggestion, as I would not have considered it with the cars being essentially brand new. I clean the rails with a piece of HO cork roadbed which usually works pretty well, at least for the sound equipped engines. Due to the light weight of the cars, maybe they are more sensitive??? 
I ran the two locos and the 2 cars still with the lighting reactivated in back and forth over about 30' of layout several times with only an occasional and brief blink of the blue LED indicating that the board sensed the need to limit current. took the following video showing how the rocking the car side to side caused the blue LED to blink. I could not get this to happen to a Rapido Horizon car with lights

/>
I am going to guess component B1 is a bridge rectifier??? To add a capacitor/resistor/diode along the lines of what you recommended for the Kato light circuits, is this where it would be wired in? If I'm going to have lights in cars, I absolutely want no flickering AT ALL. It looks better with no lighting at all rather than flickering.  It also means I have to populate it with passengers, although that is an artistic issue, not an electronics issue!

I had taken a board out to send you, but should we bother at this point?

Everything is fine as long as the wheels and track are clean.

However, I'd be inclined to lift one leg of the capacitor and install a small value (~100 ohms) between it and the circuit board.
See if that prevents the blue LED on the DCC unit from flickering.
If so, then consider increasing the value of the capacitor until the lights stay on with less than clean wheels and/or track.

[peteski]

Yes, that is the right idea, but with those SMD caps it is pretty impossible to lift one leg without pulling up the other pad.  Cutting one of the traces and installing a resistor would probably be more realistic.  I asked Rick to send me one car to come up with a workable (for him) solution.

I'm still surprised that charging 47 uF cap would cause enough of a current spike to trigger the warning.