Hello All,
I am in the process of upgrading the OEM decoders in seven HO Bachmann Geeps.
Four are GP40s and three are GP30s.
The four GP40s are MU'ed in one consist while the three GP30s are MU'ed in a separate consist. The OEM Bachmann decoders don't support advanced consisting.
I read an article recently on the purpose of the caps.
Apparently, they are a requirement in E.U. countries to prevent any RF interference of the motors.
The article went on to say that unless you are trying to listen to the radio or watch over the air T.V.- -within inches of your model railroad- -the caps are unnecessary.
It went on to say that the resistors chokes can interfere with the B.M.F. function of most modern decoders.
Three of the GP40s motors have flywheels. The fourth, without flywheels, runs faster than the others.
Current motors available from Bachmann for GP40s don't have flywheels.
I have contacted Bachmann to see if they had any of the older motors with flywheels. Alas, they don't. So I'll be re-motoring three of the four.
I have upgraded all of the GP40s to Digitrax DH 166 series decoders.
Yes, I can speed match them with CVs but I'd rather start with all four mechanically similar.
For the GP30s I'm installing Digitrax 126 series decoders.
All of the motors in the GP30s are the same with flywheels.
The frames in two of them are the horizontally split type with the DCC ready PCB with NMRA 8-pin sockets.
The third is the vertically split frame with a factory-installed, OEM, DCC, PCB.
Bachmann offers a replacement PCB with an NMRA 8-pin socket for this unit.
I have only removed the caps and resistors from the GP40s while hardwiring them in anticipation of re-motoring them.
Today, while running the GP30s, they were bucking and fighting each other. I thought that one had a cracked coupler from the dogbone to the worm gear- -a common problem.
I took all of them apart, removed the caps and resistors chokes, and put them back together with the OEM Bachmann decoders.
They are all running smoothly MU'ed in a basic consist as I write this.
It has been said that adding a decoder to a locomotive that is not mechanically sound will not improve the performance.
Now I have seven locomotives that will benefit from the addition of upgraded decoders because of their mechanical soundness.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
I believe flywheel action has been implicated in poorer BEMF sensing, too.
A good high-frequency PWM drive from a decoder is capable of doing most of the 'smoothing' a flywheel historically provides. While a flywheel can also compensate for momentary drive-power failures, decoders without keepalives are likely to try resetting on the usual causes of such failures anyway.
It may be that, for DCC-only operation, keeping the flywheel after removing the caps and 'resistors' (that are there to minimize sparks between brushes and comm sections; LRC filter) might not be fully desirable
I only have a handful of Bachmann locomotives. I remove the cap and choke from the motor-side of the circuit on all of them. The RF interference was probably only a problem with cheap AM radios. Don't have to worry about that anymore. Yes, the EU requires it so B'man installs it on everything.
Good Luck, Ed
yes, the cap is for emI radiation, it can be removed ...
however there is no resistor on there, what you may be seeing is a choke, which also can be removed ..
where did you get the idea that it was a resistor ???
I run DC, I remove factory decoders, I have a lot of Bachmann locos, mostly steam, just a few of their diesels.
I use Aristo Craft Train Engineer wireless radio PWM throttles.
For nearly two decades it has been, I thought, pretty common knowledge to remove the caps from the motor circuit on these locos. I have been rmoving them for at least that long.
It generally results in much improved slow speed operation with no negative effects.
Honestly, if I was to ever go DCC, I would completely remove all factory lighting boards and hard wire decoders with a minimum of other components in the circuit.
And yes I have heard others say removing them improves performance with DCC as well.
Somewhere, hidden in the history on this forum and the Bachmann forum, and likely others, are photos and instructions for many of the various Bachmann products regarding this.
Sheldon
Could be why Bachmann uses those not-so-good decoders. They don;t have high frequency PWM drive, so they the capacitors don't do much damage there, and they don;t have BEMF, so there's no interference there. There are some that say operation improved even witht he Bachmann decoders if the caps are removed - I don;t doubt it. But with a better quality decoder - they definitely will interfere with operation. The inductors do not have to be removed - they are in series with the motor power, so if you do remove them, they need jumpers to replace them, but the filter effect is caused by the cap and inductor working together - a circuit called an LC filter (inductors are traditionally referred to using the letter L, like capacitors are C and resistors are R).
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Those are 4.5 microhenry ferrite chokes. Look up the color values on the Internet. I have measured them with an LC meter. No resistance, The style is different.
A couple of my locos had coil wire types.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
All I have read the past few years is that everyone completely removes the caps.
Some PC board have surface mount caps that have to be clipped.
Some locos have the caps and chokes under the loco cab.
Some have the caps across the motor leads.
Bachmann sells a lot of DCC locos in the UK and that require filters so they include this in USA locos.
wvg_ca(W)here did you get the idea that it was a resistor???
Well...
It looks like a resistor with colored value bands.
So...
I just Assumed.
You know what happens when you Assume!!!
jjdamnit I just Assumed. You know what happens when you Assume!!!
I just Assumed. You know what happens when you Assume!!!
lol!
It is a cruel trick by us EEs to make two components look exactly alike to the untrained eye. You won't confuse a capacitor for a resistor, no matter what type of capacitor it is, but those small inductors - we just want to make sure everyone is paying attention.
Yes, the Bachmann capacitors can be anywhere - they aren't particularly consistent but it seems like the trend is to put th emotor capacitors on the board now instead of directly on the motor. But your model may vary. If retaining the factory board and just plugging in the decoder, there are sometimes other capacitors as well, used to help with headlight flickering more than anything, unrelated to the motor drive circuit. Thus my suggestion as well that in most cases the factory board should be removed and avoided. There are far better solutions now, and you don;t necessarily have to wire the decoder in. Especially for diesels and people who want additional lights beyond basic headlights, the Decoder Buddy boards have LED resistors preinstalled, and have 2 plugs - one for the decoder, and one to feed the wires to the lights, so the ability to just unplug and completely remove the shell is built in. Those split fram Bachmanns likely won't fit such a thing though, there is not a lot of space without doing some work to the frame. In that case, removing the factory board to leave the most possible space for the decoder is probably the best bet.
The first time I saw the chokes I knew they were not resistors. The colors were not the usuall line up for resistors. A dead give away. I dragged out my LC meter.