Speed synchronized sound - "distortion"

[mdh8]

I have a large scale night before Christmas set with speed synchronized sound. The sound works well for the most part and it changes appropriately with train speed. Unfortunately, every so often - maybe every 10-15 seconds - it makes a distorted noise that I can't describe any better than a loud fart. Any suggestions what is happening?

[Greg Elmassian]

decoder manufacturer and model?

[Loco Bill Canelos]

Greg,

It is a Big Hauler 4-6-0 with the Bachmann stock simple sound board in the tender,  no decoder.  Right now all I can think of is there could be an intermittent short, or a dirty chuff sensor on the back driver.  The sound described is what I hear when I test the sound by unplugging the chuff sensor and shorting out the board to see if the sound board works.   I would be sure is was a short, but for the fact that the strange sound is occurring every 15 seconds.

Hi Mdh8,

This is a tough one to diagnose without being there.  So is there any speed when the sound does not occur, like very slow, or full throttle??  If it occurs at the very slowest speed, does the sound take longer to happen?

Let me know and we will go from there.

Loco Bill

[tedyarbrough]

Friends,
I seem to recall SEVERAL years ago there was a problem with the stock sound system causing a noise. I think it was called a 'Burp' at the time. I do not recall the fix. I looked quickly at http://www.girr.org/girr/tips/tips4/bachmann_sound_tips.html and did not find anything about the 'Burp'. Someone might remember and lead mdh8 to an answer.
Happy Rails To You,
Ted

[mdh8]

Yes, maybe "burp" is better. I just got it back out to do some testing - we haven't even put a battery in the last couple years because of the issue. (Un)fortunately I could only reproduce the burp once over a range of speeds. From what I remember, the train would burp periodically, but not at a regular interval. Frequently enough that it wouldn't make it more than a lap or two around without a burp. It would happen over a range of speeds, and I don't recall it being drawn out at lower speeds - a very consistent noise.

Perhaps it won't return but if it does, I appreciate the insight.

[mdh8]

Another ten minutes of running and it's been doing it a bit more regularly again. I'll try sharing a video: https://streamable.com/nbtdiq

[Loco Bill Canelos]

Well that video is very interesting, but I am at a loss to figure it out, except for the old battery.

Right now the only thing I can think of is to try a brand new 9Volt battery, since yours is very old.  When you take it out look for corrosion on the terminals. and on the tabs the battery rests on, and see if they are clean.  Since the burp occurs more frequently the longer you run it then I definitely suspect that the battery may be getting low. 

Bill

[mdh8]

Sorry for the confusion - it's a new battery. No corrosion evident on it or the terminals.

[Loco Bill Canelos]

Ted is right about about similar problems.  Up till today I wasn't able to find anything at all in the forum history, so I went all the way back to 2007 and found this:

"What is happening is the sound drum contacts (the strips on the drum) have screws at the ends holding the strips to the plastic drum. The Mk. IV and later 4-6-0 the axle bushings are LARGE, and the screwheads occasionally contact the bushing, which is one side of track power.. As the axle moves from side to side, the gap closes and you get, the "fart" effect.

The cure is to put a nylon washer between the back of the drive wheel and the brass bushing. The proper way to do this is by removing the wheels, but I've been successful on may occasions by just cutting one side of the washer and "persuading" it over the axle with some needle nose pliers.

I believe the original problem and cure was posted on the Phoenix Sound web site, but I don't know if it's still there.

I just checked and it's here and even includes picture of the process I just described and the size of the washer needed.

http://www.phoenixsound.com/pdf/Bach10W.pdf  (page 3)"

If you click on the link it will download a PDF. scroll to the bottom where you will find the fix they recommend, just disregard all the info about installing a Phoenix System. 

Bill

[mdh8]

Fantastic! Thanks so much!

[Loco Bill Canelos]

You are very welcome, but we really owe Ted.  I had totally forgotten that old problem, if it had not been for Ted, I would still be floundering around trying to figure it out.

So a Big Thanks to Ted for getting us on the right track ( pun  intended!!!)  after we went down the wrong branch.

All the best to you and Ted

Bill

[tedyarbrough]

Bill and mdh8,
Always glad to help! I enjoy garden railroading/g scale trains and want others to as well.
Happy Rails To You,
Ted