LionChief Curcuit Board with 4 Ohm load?

Perfectly logical reasoning for this application.

I was joking about the Spikes.  I don't believe they are of a long enough duration to cause excessive heating in the cap, ie failure.

The bottom of my AC/DC Buck Converter board is different than the one represented on the order page.  On the one I received, the DC Input appears to be incorrectly labeled AC Input and the large capacitor is connected differently (unless I am looking at it wrong?).  Take a look:

Depicted

What I received:

John

I would put AC or DC in on the AC terminals.  Since it's a full-wave bridge, it'll handle DC just fine on the AC terminals.

@gunrunnerjohn posted:

I would put AC or DC in on the AC terminals.  Since it's a full-wave bridge, it'll handle DC just fine on the AC terminals.

Thanks John.

Good to know.

And in terms of a current keeper capacitor to be clear I could solder that to the bottom right where I labeled Lg Capacitor on the photo above.  Is that correct?

John

Yep, right across that large input cap, make sure you get the polarity correct.

@gunrunnerjohn posted:

Yep, right across that large input cap, make sure you get the polarity correct.

Of course.

Thanks again John

John

UPDATE:  Tried an 8Ω 0.5W speaker (with the baffle).  Again, no difference in loudness, just a slight reduction in base response.

Will try the amp with the current keeper capacitor next.

John

Sad follow-up.

Grandson's original amp board fried.

Was able to use the HiLetgo amp fed by the AC/DC buck converter with a current keeper cap as mentioned above.  Using an 8Ω speaker (original) it sounded great and no interruptions going over switches.  Adjusted the pot on the amp to reduce the level feeding the speaker (no pad on the input from the LC engine amp) and it was plenty loud.  Better than ever.  So I ran it for awhile.

Then it derailed at a switch and shorted out popping the Sensata breaker connected to the Z1000 (usually not a problem).  Just reset it.  There are also a TVS diode attached to each end of the two loops.

Except now there is no sound at all even when put back at the stock configuration.  No Bluetooth chirp - nothing except a hum.  When Bluetooth remote is turned on the engine moves forward and backward, but the sounds are gone.  Tried the Bluetooth app on a tablet - no sounds with that either.  So engine controls work, Bluetooth works, sound does not.

Unless there is some miracle anyone knows about I am assuming I have to open up the Lion Chief engine and replace the entire amplifier board.

I knew the risks when I started this project.  My grandson is coming tomorrow so I'll let him know what happened. 

Thanks,

John

I doubt there's a miracle in the offing.

@gunrunnerjohn posted:

I doubt there's a miracle in the offing.

I think the board is $75.  I just have to find disassembly instructions.

Thanks,

John

John sorry to hear about the accident.  Good luck replacing the LC board.  Who knows, maybe the new one will be louder...

@SteveH posted:

John sorry to hear about the accident.  Good luck replacing the LC board.  Who knows, maybe the new one will be louder...

I thought of that.  At least others who find this thread will have an idea of what one faces ahead of time.

Thanks,

John

Increasing the sound volume on a Polar Express that is on a Christmas layout prompted me to go through this post. Since its been over a year, has any new hardware or ideas on how to accomplish this shown up?

TVS are connected to pickups on all my locos that have circuit boards as well as AirPac breakers on the ZW.

I was thinking of adding a speaker, Buck Converter and amplifier to a passenger car just behind the tender and putting a tether that connected the tender speaker output to the  passenger car amplifier input.

@Santa Bill K posted:

I was thinking of adding a speaker, Buck Converter and amplifier to a passenger car just behind the tender and putting a tether that connected the tender speaker output to the  passenger car amplifier input.

Keep in mind that it's likely that any amplifier power supply would have to be totally electrically isolated from any track ground or power.  A common ground is unlikely considering the way that most speaker amplifier circuits are designed on our model train electronics.  Power is an important consideration in a project like this.

Considering using the Buck attached and the Stereo amp attached with one 1.5" speaker (not sure that the 2" would fit in the bottom of the Polar Express passenger car) for each channel and sending the same input to both of the channels.  I think that 2 speakers and the amp would provide plenty of volume. On the grounding consideration: The Buck would be powered by the same pick up roller as the lights in the passenger car and the ground from the wheels same as the lights. The Buck would power the amp. The input signal would come from the speaker connection in the Tender.  The amp input impedance should be high enough to not have much affect on the output of the Tender amp. The Buck and amplifier would be isolated from the frame of the passenger car. A new tether made of the small power connectors that you frequently refer to will carry the audio signal from the tender speaker to the stereo inputs.

LED upgrade is already in the passenger cars. (Rod's kits)

Would this provide the adequate ground isolation that you are referring to?

Any suggestion on using different parts?

Thanks for sharing you wise council.

Having a problem with 60hz hum when the PE Tender speaker is connected to the amp.  Suggestions on what to try to get rid of the hum?

Pardon lack of my skill to make a schematic.

Adjusted the output voltage on the Buck to 5v with the AC track input anywhere between 8-19v. Could switching the AC input  polarity be a fix?

Question: After first disconnecting power to the aux amp, if you disconnect its audio input while the aux amp is still connected to the aux speaker, does it still hum when the amp is repowered?

If not, inserting an audio isolation transformer before the aux Amp's audio input should get rid of the unwanted hum.

Audio Isolation Transformer options link here.

My hypothesis is that if everything else is electrically isolated, with 2 different power supplies: the first amp's output has a different DC potential from the the aux amp's input.  In which case the audio connection between them would be normalizing the DC voltage.  The power supply ripple currents may be the source of hum.  An audio isolation transformer inserted into the audio path between the amps should complete the DC isolation and eliminate the hum.

Disconnected the power to aux amp by taking the roller and wheels off the track. Disconnected the audio input to the aux amp by disconnecting the connector to the Tender speaker. (wires under the green painter’s tape). Placed wheels back on track and powered up. Aux amp still connected to the aux speakers. No hum in this configuration. The hum goes away any time the audio connector to the Tender is disconnected and power is still on to the power supply and the aux amp.

So the audio isolation transformer is the fix. There is .75 by .75 inch of space so this will fit in the car and can sit where the audio is coming in now. I don’t need to be concerned with any frequency below 50hz.

Added a picture of my mess inside the Baggage Car which is all plastic. Only metal is the roller, wheels and axel. The sounds of the horn, bell, chuff, and announcements were loud except for the hum. Anything I have missed in my assumptions?

Do you have any other suggestions?

Communicating with an expert makes short work of problem solving. Thank you Steve.

@Santa Bill K  Thank you for the compliment, however when it comes to such things, I consider certain others here on the forum to be the real electronics experts.  Maybe wait until one of them weighs in before buying the transformer.

In the meantime, could you please try re-posting the picture of the inside of the baggage car, it's not coming through on my end.  This is what I see:

Thanks for letting me know.

Try this

Pretty sure my post of a couple months ago is likely the issue.  The totally isolated power supply is the key if that transformer doesn't do it.

@gunrunnerjohn posted:

Keep in mind that it's likely that any amplifier power supply would have to be totally electrically isolated from any track ground or power.  A common ground is unlikely considering the way that most speaker amplifier circuits are designed on our model train electronics.  Power is an important consideration in a project like this.

Thank you chiming in John.

I must not understand how to get "fully isolated". I thought that the BUCK converter nor the amp should touch ground. The car body is plastic and they are mounted with and on non conductive material. Is it the power from the roller pickup and wheels that sends AC to the BUCK that is providing the ground path? I thought that the BUCK converter would be the isolation in this path since it converts AC to DC and regulates the DC. If that is the issue, how can DC power be provided for the amp?

The audio feed comes from the Tender speaker. no ground in the Tender. Is the ground path through the amp in the locomotive?

@Santa Bill K posted:

Thank you chiming in John.

I must not understand how to get "fully isolated". I thought that the BUCK converter nor the amp should touch ground. The car body is plastic and they are mounted with and on non conductive material. Is it the power from the roller pickup and wheels that sends AC to the BUCK that is providing the ground path? I thought that the BUCK converter would be the isolation in this path since it converts AC to DC and regulates the DC. If that is the issue, how can DC power be provided for the amp?

The audio feed comes from the Tender speaker. no ground in the Tender. Is the ground path through the amp in the locomotive?

The buck converter has one input power lead coming from track voltage.  Yes, it has a bridge rectifier, but the negative isn't totally isolated from track power.  The problem is the power is not totally isolated from the input.

The Lionchief speaker drive common is not at the same potential as the negative power supply output from the buck rectifier.

You can try a simple experiment if you can't get rid of the hum the way you're attempting to now, that will either verify that this is the problem or disprove it.

The test: Replace the buck converter with a simple DC wall wart on a bench test.  Wall warts are completely isolated from the primary and will provide a floating DC output voltage.  If that eliminates the hum, then you need a fully isolated DC supply.

A fully isolated supply is one that has an internal transformer in the mix so that there is no current path direct from the primary power to the secondary power.  It's the same principle as all the 120AC --> 12VDC wall wart's use, there's an internal transformer that blocks any direct connection between the primary and the secondary.

Check this description of DC-DC Isolation.

Here's a 12V DC-DC isolator 2W

Soldered the wall wart into the BUCK. The voltage regulation of 5V DC from the BUCK remained the same.  NO HUM. Everything sounded great.  Added the DC-DC 12V Isolator. Chuff was fine. Activating the horn, whistle, or talk made a pop, about 2-3 per second start. Disconnected the wall wart and connected track power. NO HUM on the chuff. Activating the horn, whistle, or talk made the pops start.

Video attached show the car and the sound of the pops.

What is causing the pops?  What should be changed?

That sounds like feedback, possibly an input/output impedance mismatch.

Did you put an 8 ohm load resistor on the existing LC amplifier output?  Probably a 1W 8 ohm resistor would do the trick.

I did not put anything other than the connection to the Tender speaker on the output of the amp.

I have a selection of 1/2 W metal film resistors (BOJACK). Please check my power and equivalent resistance calculations.

3 x 22 ohm resistors in parallel ~7 ohms, 1/2 watt each should dissipate the power?

Yep, and for safety sake, just use two of them.  The impedance isn't critical, 11 ohms is fine,  but you just need a load on the output of the original amplifier output.  I'd rather have a higher impedance than potentially overload the amplifier.

The Tender speaker output measures 7.7 ohms DC when the track and loco are dead. Measures ~1 ohm when it chuffs or horn, whistle, talk is activated.

I'll add the 11 ohms 1 W to the load.