New MTH Smoke unit problem

Don't have a newer laptop. Layout / tiu is upstairs. Don't even know if the tiu version is compatible?

Resurrecting an old thread due to some odd behavior...

I have a Chicago Great Western RS3 (30-20818-1) that had the smoke problem.  About a year ago, I performed the update and thought I had fixed the problem.

Earlier today, I put the engine on the track for the first time in awhile - I had a visitor whose grandfather worked on the CGW who wanted to see it.  The engine started smoking profusely (like the video earlier in this thread).  Tried adjusting the smoke and turning it off and on, but the smoke function was unresponsive, so I shut it down before melting anything.

Thought I might have to redo the file update.  A couple of hours later, I put the engine back on the track; it wouldn't respond to DCS.  So I deleted the engine and re-added it.  Lo and behold, the smoke function worked perfectly - could turn it on/off and adjust the amount via the remote, and it wasn't smoking profusely as it had earlier.

While I'm happy that I didn't have to reload any files, I'm at a loss as to how to explain the excess smoke and the ability to make it correct itself by deleting and re-adding the engine.  Hoping that one of the DCS experts can provide an explanation regarding what happened, and also let me know if there is any ongoing risk of a meltdown.

Thanks in advance.     

My concern would be that the smoke resistor was shorting to frame ground. By shear luck you did not blow the board sky high, but that could easily explain huge amounts of smoke and not being able to control it.

Again, because the single resistor small units have the resistor at an angle and the small cup size, it is relatively easy to get a short in these in my experience.

@Vernon Barry posted:

My concern would be that the smoke resistor was shorting to frame ground. By shear luck you did not blow the board sky high, but that could easily explain huge amounts of smoke and not being able to control it.

Again, because the single resistor small units have the resistor at an angle and the small cup size, it is relatively easy to get a short in these in my experience.

Thanks for the reply.  Based on your info, I opened it up.  Found some burnt wicking, which would seem to make sense since the engine had initially been run prior to the file reload and considering the heavy smoke that was observed yesterday.  Did not see any burn marks indicating that it had shorted, and the resistor wires did not appear to be bent out of their normal position.  I certainly see what you mean regarding the mounting of the resistor - there's very little clearance between it and the body of the unit.

I put it back on the track; it smokes properly and the smoke unit responds to commands for on/off and volume, so all appears to be well now.

Would it be a good idea to insulate the resistor leads from the body of the unit, perhaps with electrical tape?

@Mallard4468 posted:

Thanks for the reply.  Based on your info, I opened it up.  Found some burnt wicking, which would seem to make sense since the engine had initially been run prior to the file reload and considering the heavy smoke that was observed yesterday.  Did not see any burn marks indicating that it had shorted, and the resistor wires did not appear to be bent out of their normal position.  I certainly see what you mean regarding the mounting of the resistor - there's very little clearance between it and the body of the unit.

I put it back on the track; it smokes properly and the smoke unit responds to commands for on/off and volume, so all appears to be well now.

Would it be a good idea to insulate the resistor leads from the body of the unit, perhaps with electrical tape?

I would think electrical tape, heatshrink and many things would cook and melt that close to the resistor body. Probably has to be a much higher temp rated material.

Again, I would think that electrical tape would just result in a burning stinking plastic smell.

Some of the MTH original cups used Mica insulation that went around the inside walls of the metal cup, but never saw that sold as a part.

This part is for voltage regulators but might be able to be used in the corner bent into an "L"

You also could probably just buy Mica sheet insulation material and cut to size.