Super-chuffer cab light flicker

One of our club members had this happen with his similar install. He believes the inconsistency in track voltage around the club layout causes it as it runs fine at home where it sees a solid 18VAC. How well is the  voltage distribution around your layout?

If you are using an incandescent bulb in the cab light, don't power it from the Super-Chuffer.  I use a 12V incandescent and wire it from the cab light control to track power. 

The DC supply on the Super-Chuffer is limited in the amount of power it can provide, and powering too much off that supply results in the symptoms you see.

One "fix" for lower voltage on the tracks is to add a parallel filter cap to the Super-Chuffer power supply, this allows operation with lower track voltages.  I've used this technique to allow the Super-Chuffer to run for conventional operation.

There is hysteresis in the turn-on and turn-off of the cab light, so unless the chuff rate is varying, you should get the lights turning on and off.

Thanks, everyone.

I'm using the stock incandescent light and it was already powered via track power.  I'm guessing I had 5 to 7 hours of run time on the loco (post super chuffer install) before the symptoms started showing up.  I power my layout (modest size) with two PH-180 transformers and try to keep the track clean, so I don't think I have a power issue.   

I would like to install the filter cap - GRJ, can you provide thoughts on the specs?  Do you put the cap across the roller and ground inputs on the super chuffer?  What about polarity (any DCS side effects)?

The cab light blinking is definitely in sync with the chuff signal.  Also, the headlight (converted to an LED) dims a bit when the cab light comes on.  Another new symptom is that when Aux 2 is pressed to turn the headlight on or off, the loco lurches a bit when its moving.  When the engine is not moving, and Aux 2 is pressed to turn off the headlight, the headlight starts to slowly fade/flicker.

Thanks for all the help!  

I think there is a grounding or power supply issue to the S-C board, that doesn't sound like anything I've seen before.

Thanks, John.

I’m hoping to open it up this weekend to troubleshoot.  While I’m in, what capacitor would be okay on the power input for the chuffer board?  Also, what’s a good strategy for replacing the incandescent cab light with an LED?

Thanks for all the help!

I just realized that I did omit the most likely source of your problem!  One issue that I have seen is the smoke fan motor can draw excessive current, this will create a host of problems with the Super-Chuffer as the power supply is only designed to run a properly working fan motor drawing no more than 50ma maximum, and usually more like 30-40 ma.  If the motor draws excessive current, it will cause the symptoms you see.

I can't even imagine what would cause the locomotive to lurch when you change the headlight status, the Super-Chuffer draws no power from anything on the locomotive.

The incandescent light doesn't have to be replaced if you're powering it off track power like the current diagram illustrates.  I find the incandescent is a better light for the cab, the LED light is too focused and doesn't evenly illuminate the cab.

The capacitor goes across two pins of the power module, after the diode in the circuit.  A 1000uf 35V capacitor allows the Super-Chuffer to run at significantly lower voltages.  The extra capacitance isn't normally needed.

Thanks, John.

I'll measure the current on the smoke motor.

I really appreciate all of the knowledge you've shared!

I will be interested in what you find.

I was able to measure the smoke motor ampeeage tonight.  It was drawing 27 milliamps while on 5 Volts dc from my benchtop power supply. 

I checked for loose connections, crimps, etc., but havent found anything obvious.

When I put evergthing back together, the loco ran normally for about 50 feet before the cab light started blinking again.  It was blinking in sync with the chuffing.

i dont have a spare super chuffer to swap in, so any other trouble shooting thoughts are appreciated.

Thanks!

i havent installed the capacitor yet.

It certainly sounds like a power or grounding issue to the board if the fan isn't drawing excessive power.  Can you measure any voltage drop between the ground on the Super-Chuffer and the frame ground?  Same question for the track power connection to the center roller.

Another thing to check is the two capacitors next to the square power brick.  I've had the same style have a leg loose on my lighting modules, those are necessary for the power supply to function properly.  What you're seeing sure sounds like a power supply dropout issue.

Good news, the symptoms have gone away (not sure I found a cure, because I couldn’t find an obvious cause).

I took the shell off and set up the loco on a roller test track so that I could take the recommended voltage measurements.  I couldn’t get the symptoms to repeat under normal 18V operation (I could get them to repeat if I dropped the voltage down to around 12V).  I checked thoroughly for obvious problems and couldn’t find anything.

I put the loco on the layout and ran it again with no symptoms.  I loaded up the layout with three steamers (including the problem loco) and had 8 passengers cars with incandescent lights. Voltage around the layout never dropped below 16.5 volts.  

I reassembled the loco and had a good running session tonight.

my theory is that I had gotten lazy with powering up my layout and not pushed the ZW-C handles all the way forward.  They are down low in a cabinet, so it would be easy to not push them all the way forward.  Otherwise, my dissasembly and reassembly put something back to happy....

I need more troubleshooting practice!!!

Thanks for the troubleshooting tips.  I enjoyed chasing the problem, even though it eluded me.  

John, I really hope your able to make some more super chuffer and chuff generator boards!  I’ve got a few more steamers that would be a lot of fun to upgrade!

Glad you sorted it out, even though it remains a mystery.   Low voltage is a likely cause, that's exactly the symptoms you'd see.  If the voltage drops down to around 14 volts, the S-C may exhibit those symptoms.  The larger add-on capacitor would have made it go away, but then you'd never actually know what was causing it.