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I have the Lionel 26860 Railsounds boxcar.  Lately the bell starts ringing at startup.  Eventually I can get it to stop with the sound activation button, which is wired for whistle.  The bell button on my Z4000 will start but not stop.  Whistle activates only occasionally, sometimes with the Z but more often with the activator.  Any miracle cure advice?  Is there a wire I could cut to eliminate the bell, which I don't use anyway?  Is the Z an "incompatible" transformer for this product?

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@jps32016 posted:

I have the Lionel 26860 Railsounds boxcar.  Lately the bell starts ringing at startup. -typically indicating the car is seeing a DC offset on the incoming AC power

Eventually I can get it to stop with the sound activation button, which is wired for whistle.

The bell button on my Z4000 will start but not stop.

Whistle activates only occasionally, sometimes with the Z but more often with the activator. Why is there an additional sound button wired in series on the Z4000?

Any miracle cure advice?

Is there a wire I could cut to eliminate the bell, which I don't use anyway? There is no wire you can cut. This is a sound board that senses a positive or negative DC offset within the AC power it is receiving from the track. If you cut a wire- you get no sounds.

Is the Z an "incompatible" transformer for this product? The MTH Z4000 specifically was designed to produce nearer a true sine wave format and be the most compatible with most items- especially those expecting pure sine wave.

As a guess, you may have something in your wiring, dirty track, maybe some other car, or something causing a small DC offset on your track.

Again, I would clean the track and wheels- oxides can cause a metallic diode effect and create DC offsets. I see no reason for a second sound activation button when using a Z4000 with both bell and whistle DC offset functions.

Is there anything else besides the sound button wire in series between transformer and track? Example a TIU or some other device? Any TVS diodes installed?

Okay thanks for the quick reply.  No DCS, just the Z.  The layout is actually on the floor of my workshop/laundry room, so the track can probably get dirtier faster.  But the newer Trainsounds systems I installed with a steam loco and diesel AB unit work perfectly.  I also have a similar Railsounds diesel car which sometimes acts up as well, so I'll try the cleanup and take the activation button offline.

Thanks for the tip, Vernon.  I probably knew something like this many years ago but didn't occur to me now.  Gave the wheels a good cleaning.  The diesel car is working fine with the Z, and the B&O steam sounds car is good too, but will only respond with the Lionel activator, which is okay, but hard to understand why.  I also have a 1980s Railsounds car which I don't use anymore but it does work with the Z. 

@jps32016 posted:

Thanks for the tip, Vernon.  I probably knew something like this many years ago but didn't occur to me now.  Gave the wheels a good cleaning.  The diesel car is working fine with the Z, and the B&O steam sounds car is good too, but will only respond with the Lionel activator, which is okay, but hard to understand why.  I also have a 1980s Railsounds car which I don't use anymore but it does work with the Z.

Not that hard to understand- the circuit is looking for a specific distortion or change- we call a DC offset in the AC waveform.

The external button produces this distortion using simple diodes in series, in one leg of the AC to the track. The button is normally closed bypassing the diodes as if the button was not there. When you press the button it opens that path of the circuit and now the diodes wired in parallel to the switch but ultimately in series to the track- now the power goes through them conducting only one way in DC.

The Z4000 transformer uses 4 transistors per channel to modify the AC waveform (well that and a whole lot of other circuitry) to make the variable AC waveform power output. To make the DC offset for whistle or horn, the signal firing the transistors is modified and the resulting AC output is modified. That said, it's not the same thing as just inserting a series string of diodes in the path. It simulates some of that effect- but again not the exact same thing.

Most sound cards/boards are only expecting a limited amount of DC offset, this is because older Lionel postwar transformers used copper disk diodes to produce the offset and those are not "perfect" diodes by comparison to silicon modern diodes. Basically they produce a lesser DC offset.

At the end of the day, you have identified one or two of your sound cars are "picky" about how much DC offset and basically not as good a sensing the difference between a real bell or whistle signal, and what signal they may or may not be seeing on the track.

I'm sure I have one or two examples of this (overly sensitive or not sensitive enough) in my own collection.

These are limitation of conventional operation, it's a less than perfect system, noise, track resistance, distortion of the AC sine wave, aging capacitors in sensing circuits that change value over time- all could be reasons why it's not detected or overly detected (bell or whistle/horn DCS offsets).

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