# can I remove bachmann motor circuit boards?



## DrTechDaddy (Sep 1, 2012)

I'm converting my Bachmann Thomas&Friends locos to battery power.

The Bachmann loco has two circuit boards installed, one across the motor terminals and one across the polarity switch. The motor one seems to be some kind of L-C filter.








1. What are these boards for?
2. Can I leave them in place when installing DCC or other PWM motor-driver circuit?
3. If I remove the circuit on the motor and connect the motor leads directly to the track (when running with track power) will it have a negative effect on the operation of the loco or generate unacceptable interference in a home or garden or club setting?
4. If NO to (2) and YES to (3) above, would it work to wire a DPDT between filter circuit output and motor input for switching between track and battery power, or would the extra lead length defeat the function of the filter?


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## Greg Elmassian (Jan 3, 2008)

1 noise reduction
2 sometimes, but better to remove
3 it can
4 no it won't work, the length of the wires to the switch essentially negates the noise supression.

Greg 1,110


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## Scottychaos (Jan 2, 2008)

I dont really understand what points 3 and 4 are talking about, but here is what I did with my Bachmann Connie:

Converted to Airwire, Phoenix sound, and battery power.
Ripped out every single circuit board in the locomotive.
Only thing left was two bare wires to the motor, and two bare wires to the headlight.

Added back in:
Airwire receiver.
Phoenix board.
Speaker.
Battery.
Diode for the LED headlight.

I ripped out the smoke unit..I never use smoke, ever, I dont like it, so I always get rid of those those.

One thing I did lose in my "scortched earth policy" in this case was the flickering light for the firebox. I would have liked to have kept that! But this was my first battery conversion, so I really went bare-bones on it so I could really understand it. Getting rid of all the circuit boards works fine! Its really "battery only" though, I killed all track power access, 

For future conversions, I dont want to go quite so extreme with ripping out everything. Im going to use battery-only at home, but my Garden RR club does many displays and train show setups with track power. My 2nd conversion is going to be a Bachmann Spectrum mogul. I would like to keep full track power! Lights,flickering smokebox, and all..but then also wire in a battery car with airwire. Ideally I would like to end up with a switch, flip one way for track power,flip the other way for battery power. I have no idea how to do that yet!  but thats my next goal.

Scot


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## DrTechDaddy (Sep 1, 2012)

Greg--thanks.
Looks like if I want PWM speed control, I need to give up "noise reduction."
Guess I'll have to revisit this if I ever get any complaints.

Joe


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## Greg Elmassian (Jan 3, 2008)

It's mostly DCC decoders that are affected by the noise circuits. Most DCC decoders use BEMF measurements to better control the motor. Those noise circuits can confuse the "readings". I don't run a lot of Bachmann or Piko, so my Aristo and USAT and Accucraft and Berlyn locos do not have these circuits, so can't give you direct experience on which locos and which decoders. You can leave the circuitry on and see if the loco runs funny, and if it does, take them out.

Scot, I thought questions 3 & 4 pretty clear... he asked if removing the noise reduction circuits on the motor will affect things, and it does... (pretty clear that the manufacturer added these because they HAD to, no one does anything for free any more ha ha!)

Question 4 was could he switch these controls in and out... not practical since your motor would stay connected to the decoder whether running DCC or DC.

Greg 1,109


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## DrTechDaddy (Sep 1, 2012)

Greg,
I was concerned about even "trying" to connect PWM with the filter in place as I've seen a couple DCC decoders go up i smoke. But point of information: Bachmann seems to install their own DCC board with the filter in place. Of course, I'd assume their board is designed to work with their motors and filters.





 at about 2:40


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## Greg Elmassian (Jan 3, 2008)

That's something to consider, but no modern quality decoder should fail with a noise filter on the motor. In the old days, many things were blamed when it was really "installer error"... the most common is a brief short between a motor lead and a track pickup lead, some of these notions are hard to get rid of. 

Also the cheap capacitors and inductors on these motors sometimes fail, but a well designed motor controller should be able to withstand a shorted disc cap. Again, in the early days, most motor controller circuits did not have short circuit protection.

So, your concern is well founded, but less and less of a concern as we use better hardware.

The filters in place are simple RC filters, a disc cap to short out noise across the commutator, and inductors in series to block any noise into the decoder..

Greg


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## TonyWalsham (Jan 2, 2008)

Bachmann were required by European law to fit "noise" suppression pcb's such as those found in the Large Scale Heisler, older 2-6-0, 4-4-0 and Connie all used two 47 mfd polarised electrolytics wired in a bi-polar fashion. Especially as in some cases they wired caps in backwards.
The "Dizzie" had them but not at the motor. They were mounted on the internal pcb.
Rip them out.
I don't think the 4-6-0 Big Haulers ever had suppression pcb's. No idea why they didn't, but the above locos did.

The LMD18200T solid State motor drivers I use do not like capacitance across the motor leads. 
3 x .1 mfd (# 104) disc or mono types with inductors is about the maximum capacitance before the motor becomes "jerky" in operation.

Thomas uses monos and inductors so I would expect them to be OK,


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## Greg Elmassian (Jan 3, 2008)

So in your experience Tony (other than failed/reversed electrolytics) has a decoder been DAMAGED from the noise circuitry?


My experience says no, but what say you?



Greg 1,094


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## TonyWalsham (Jan 2, 2008)

Not that I know of.
But then I freely admit I know zip about how DCC works.


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## Greg Elmassian (Jan 3, 2008)

Sorry Tony, I meant ANY unit that drives the motor, in your experience (I use the word decoder to mean anything that receives a signal and controls the loco motor)

Greg 1,091


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## TonyWalsham (Jan 2, 2008)

Sorry Greg. I can only comment about my ESC's.
There were a few failures long ago with ESC's using a FET and relay. Using a too small kickback diode.
I have never had a failure in the field of the Solid State Motor drivers I use. They are self protecting for over temp, overload and short circuit. on the output. I guess 5-6,000 have been through my hands over the years.

Bachmann filter boards have never actually killed any of my ESC's. However too much capacitance creates erratic motor behaviour.


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## Greg Elmassian (Jan 3, 2008)

Thanks Tony, my position is that any modern, well designed electronics will not be damaged by the filters. I think your excellent track record also reinforces this.

This was in reference to the OP being concerned that he needed to remove these right away, to avoid damage.

And my position is leave them in, try the system out, and if there is erratic behavior, then remove them.

Regards, Greg 1,086


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## DrTechDaddy (Sep 1, 2012)

Tony, Thanks for that technical info. So, if I don't run my trains in Europe, I won't go to jail for removing the filters?
But would my neighbor see snow on their digital TV? [Clearly I wouldn't, because I'd be watching my trains, not the TV!]
You mentioned DCC--which is getting a bit off-topic, but my understanding is "DCC" involves three separate "protocols". The main thing is a "constant" voltage on the track modulated by a digital signaling system which is recognized by the "decoder". Between the decoder and the motor I'm assuming is some sort of PWM motor driver.
Between the user and the "encoder" to the track is typically some proprietary signaling like "locolink" or some wireless protocol. But for battery power, I'd think the "DCC" part and decoder is not relevant, as no locos are sharing the same track power! But we still need the motor drivers and some wireless protocol connecting the remote to whatever is controlling the motor drivers. And DCC sound adds another dimension! 
Now "BlueRail" is offering BLE receiver technology, allowing phones to be used as the remote transmitter.


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## Greg Elmassian (Jan 3, 2008)

I think you will be fine removing the filters unless you have really noisy locos.

Digital TV will be unaffected.

Yes, the output to the motor from the "decoder" is pwm. There are no modern units that provide pure DC to the motor.

I use "decoder" to mean the unit that receives the commands and power and then controls the motor and lights, sound, etc.

Yep, heard all about BlueRail, you mentioned in other post, there are several such schemes. 

Greg 1,085


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## TonyWalsham (Jan 2, 2008)

Dr TechDaddy.
I too am aware of Blue Rail and other systems that are controlled by smart phone handsets.
For a number of reasons, as yet they have not taken over the outdoor market. Could be early days, but I doubt they ever will take over. Greg and I agree on that one.

One thing you should not do, is power DCC devices with PWM output motor drivers. Some DCC devices will work OK on pwm. Most will not. The pwm signal looks vaguely like the DCC wave form to DCC decoders and they can get "confused".


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## Bill Swindell (Jan 2, 2008)

I have a solution for the flickering light that you are missing. If you buy some flickering LED's, you can put them in the firebox. Also, if you hook a flickering LED in series with the existing LED's, they all will flicker. This nay sound strange but it works. I hooked 2 LED's in series with a flickering one and a 570 ohm resistor directly across the battery power. Viola, firebox flicker alive and well.


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## Dan Pierce (Jan 2, 2008)

When using a self flickering led and a decoder to drive a second LED with pulses, I get a random flashing between the 2 leds that make a fire more lifelike. I like the gyro effect on my firebox leds.


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## DrTechDaddy (Sep 1, 2012)

TonyWalsham said:


> Dr TechDaddy.
> 
> 
> One thing you should not do, is power DCC devices with PWM output motor drivers. Some DCC devices will work OK on pwm. Most will not. The pwm signal looks vaguely like the DCC wave form to DCC decoders and they can get "confused".


I understood that the DCC decoder also functions as a motor driver, outputting a PWM voltage to the motor to control speed. That's why it can get superior low-speed operation. Of course, one would not use the output of a motor driver as input to the decoder.



> I too am aware of Blue Rail and other systems that are controlled by smart phone handsets.
> For a number of reasons, as yet they have not taken over the outdoor market. Could be early days, but I doubt they ever will take over. Greg and I agree on that one.


I suppose time will tell. But under $100 for an R/C receiver/engine-driver board I can use with the phone I already own as the transmitter is the best deal I've seen for R/C. If range becomes a problem, I'd imagine one could create a WIFI-based system. I know phones with JMRI are rapidly replacing proprietary handsets in the smaller scales.
In any case, I'm planning to give BLE a try.


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## Greg Elmassian (Jan 3, 2008)

Hmm... are you here to ask questions and get help, or just keep pimping Blue Rail?

You asked a generic question about motor noise filters... so you will get generic answers.

If you have a specific question, like "will my Blue Rail decoder need to have the noise circuitry removed", then please ask that.

The thing Tony was warning about, that you pretty much discounted, was that people will often take something like a "trackside" system, power the rails with PWM and then put a decoder-equipped locos (like a DCC decoder set to work in analog DC mode) on the track and that causes issues. This happens all the time.

There's a lot of experience here, and a lot of "generic" / "wide open" questions. If you ask a generic question, you should expect answers in a lot of different situations, reflecting the wide range of experience and backgrounds here.

Regards, Greg 1,081


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## DrTechDaddy (Sep 1, 2012)

Greg, Tony, et al
I appreciate all the answers--it's been helpful.
FYI
I am currently using G-Scale Graphics "Critter" motor drivers with battery power, 
and have been considering either G-Scale Graphics RailBoss or BlueRail for my next conversion.

I'll move the BlueRail discussion to another thread.
Joe


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## East Broad Top (Dec 29, 2007)

Dan Pierce said:


> When using a self flickering led and a decoder to drive a second LED with pulses, I get a random flashing between the 2 leds that make a fire more lifelike. I like the gyro effect on my firebox leds.


I'll have to play with that. I've got a stash of flickering yellow LEDs from those LED tea lights. Do the flickering LEDs affect other LEDs not tied to the same function output of the decoder? At one time, I used a flickering LED in a hobo camp, wired in parallel with all the other LEDs lighting my buildings on one loop of my railroad. When the lights came on at night, the campfire looked great, but the rest of my LEDs were also flickering. They were all on once circuit. 

Later,

K


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## locomansounds (Jul 7, 2017)

So much to learn with train electrics here. DCC complicated. Thank you.


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## Dan Pierce (Jan 2, 2008)

I tied the self flickering leds to a constant power source (V+) and I used additional leds and set one to gyro and the other to ditch. So, there are 3 flashing lights in my firebox.


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## Greg Elmassian (Jan 3, 2008)

Yep, some of the self-flickering LEDs do indeed interrupt the circuit, thus any other "normal" LEDs in series will flicker.

Even if they do not completely interrupt the circuit, the current passed will vary.

Greg 1,026


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