I recently pulled out the literature on one of my locomotives and I noticed something interesting. A particular mfg has left capacitors across the motor terminals even though it is DCC ready. This is to supress EMF emissions from noisy tracks and motors and to be FCC compliant. (We all know what happens when you run a powerful vacuum cleaner in front of an old tube TV...you get noise everywhere)
They went on to say that the DCC comittee said this is okay and a DCC conformant decoder should handle the capacitor.
Here's my problem with this on two folds:
1) For low speeds some DCC decoders use a kick voltage to keep the motor going. A capacitor would lessen this effect and hinder the kick start capability.
2) BEMF (back emf) relies on feedback from the motor to determine how quickly it's moving. It also monitors the timing between clicks as the brush passes the split in the commutator. A capacitor in there screws these readings all up as it affects the current (which changes with changes in resistance to the free spinning of the motor.)
The question: Wouldn't the use of a capacitor render these features as hampered at best? Normally if it was a DC only variant I wouldn't worry. But if they come DCC installed, with BEMF as a feature, then I have a problem.
Techinically speaking why should you even need a cap between the motor on DCC equipped models? Most of the electrical noise is filtered out before the motor any way.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
Yes, they do interfere with proper operation of a decent DCC decoder. They also interfere with proper operation of a DC system that uses PWM, like the Aristo system that Sheldon uses.
Yes they should be removed.
You have also found out the deep dark secret that "DCC Ready" is just a marketign term used in various ways by the manufacturers. There is no standard for this term. Maybe you do just plug a decoder in. Maybe the decoder just plugs in but you have to change the light bulbs. Maybe the decoder plugs in but you have to cut some traces on the existing circuit board. These would all get classified "DCC Ready".
You also see why Bachmann uses a really poor quality decoder int he DCC OnBoard locos - the Bachmann decoder does not have BEMF, and it doesn't even use a high frequency drive, so it isn't very much affected by those capacitors.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Cut the capacitors. With the capacitors gone, the inductors are not a issue.
This is a well know issue in many forums.
The capacitors are required on the other side of the Pond so Bachmann has to comply with the requirement.
Do a Google search for bachmann dcc capacitors.
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.
Gee, when I saw the subject line I thought it might really be something hard.
And while we are on the subject, removing the Capacitors will greatly improve slow speed DC performance even with "conventional" DC power packs.
The capacitors raise the effective starting voltage of the motor, and therefor raise its slowest speed.
This is more noticable on some locos than others, but all benifit from their removal.
And, DC users take note - some other brands like Proto and Intermountian are now putting these filter capacitors on the DCC jumper plug. They too are easily removed for better slow speed DC operation - with or without a Pulse Width Modulation throttle.
Sheldon
DigitalGriffin I1) For low speeds some DCC decoders use a kick voltage to keep the motor going. A capacitor would lessen this effect and hinder the kick start capability.
I1) For low speeds some DCC decoders use a kick voltage to keep the motor going. A capacitor would lessen this effect and hinder the kick start capability.
Actually all DCC decoders use some form of Pulse Width Modulation, the biggest difference is at what frequency?
I picked the below out of a DCC site a couple years ago.
Decoder PWM Frequencies
Older decoders used a motor drive (PWM), pulse width modulation frequencies of about 30 to 200 Hz (cycles per second). PWM takes a constant like 12-18 v dc and drops to zero volts quickly and back to the higher voltage to get effective voltages between 0 and 18V. These frequencies were low enough to cause a hum or buzz in the locomotive. Most decoders today use a high frequency drive of 15kHz to as high as 43kHz. These frequencies are above the range of hearing and that is why they are called silent. This type of drive comes with many different names, depending on the manufacturer. One of the problems with the high frequency drive is slow starts. With these high frequency drives the motor tends to act like it is on dc power and is subject to stiction, where the motor does not start smoothly. The combination of back-EMF and the PID motor control can over come this problem.
It would be nice if they simply attached the capacitor to the removable plug in DCC loco's. When you took the plug out to install the decoder, the caps would go with it.
Springfield PA
It is always about cost is the reason Bachmann does it their way.
Looks like I'm going to be pulling apart my C&O H-4 tonight to see if they removed the capacitor for the Tsunami. *sigh*
So much for ready as is out of the box.
You will find that the H4 has an all new circuit board, unlike anything you have seen in other Bachmann locos, but try as I might, I cannot remember the capacitor situation on it. But mine is non sound and now non DCC with jumpers installed.
DigitalGriffin Looks like I'm going to be pulling apart my C&O H-4 tonight to see if they removed the capacitor for the Tsunami. *sigh* So much for ready as is out of the box.
I have never been able to see the DCC install for the Bachmann with Tsunami. If you open yours up, take a picture and post it here so others can see what the install is like.
I “think” Bachmann leaves the main PC board and installs a Tsunami decoder PC board. Somehow the added board plugs into the original PC board. I think I saw something on that a few months ago.
I remember about three years or so ago, SoundTraxx made a sound decoder with speaker that plugged right into the PC board in a the Connie.
Don, I went and looked at my H-4 and then I remembered! It was really easy. The tender bulkhead snaps right out and the coal load slides forward and comes out. Then you can see the multi pin (more than eight) connector.
On my DCC only version that multi pin socket has an adpter board with an eight pin socket and the decoder was pluged into the eight pin socket. I'll beat the sound board plugs into the multi pin socket without the adapter board.
I removed the decoder and installed the jumpers.
Anyway, right near the multi pin socket on the main board is a surface mounted capacitor marked "C3". That's the one that needs to go.
I added weight to the tender as well, like I do all Bachmann tenders.
Good luck,
richg1998 Cut the capacitors. With the capacitors gone, the inductors are not a issue. This is a well know issue in many forums. The capacitors are required on the other side of the Pond so Bachmann has to comply with the requirement. Do a Google search for bachmann dcc capacitors. Rich
Bachmann has publicly stated that the European RF supression componets may cause issues with some DCC decoders, and that US consumers may remove the caps and coils if desired, and that doing so would not void the manf. warranty.
you'd think ( if it would work?? i don't know how near the motor the capacitors need to be?? ) that instead of soldering capacitors to the motor area that on DCC ready loco's they would just come up with a blanking plug that had the capacitors on it instead of at the motor??. even if it didn't do the job quite as well, would it be enough to comply with the regs???
Just remember, if you remove the coils you will need to solder a jumper wire in place of each one, as the coils are in series with the motor leads. The capacitor(s) are in parallel and can be simply removed. I haven't found it necessary to remove the coils, just the capacitor, in my limited set of 1 Bachmann loco.