On board capacitors

[richg]

A fellow in the Trains.con DCC forum was asking about cutting the capacitors on his 2--8-0 loco PC boards. He could not find them. The capacitors in his are SMD caps, not the yellow leaded cap which is what he was looking for. Some were trying to describe what the caps might look like.
I included a photo of the PC board in my new 4-6-0 and he cut the caps out of his locos. They run much better. The caps are labeled with a C Prefix. He had never heard of SMD components.
One interesting note, he had two K4's he picked up of off ebay for $35 total and go a new K4 from Bachmann for $25 for one of them that had problems. He got a new one and it did not have any caps on the PC board. He compared it to the photo I had put in. There where spots for the caps very clearly but never installed.
Suggestion that can make it much easier for trouble shooting in these forums, if you get a digital camera and a Photo Bucket account. If you can learn how to use a PC, you can do the photo thing also. Your PC is a powerful device when using the Internet.
Some do photos with their cell phone. I have done that in a pinch. I then email the photos to my email address.

Rich

[jonathan]

To paraphrase what Rich said:  a picture is worth a thousand words:



I'm guessing "C1" and "C2" are the capacitors that some folks clip out to get a smoother running locomotive.  I have clipped a few on some of my locos, but not all, like this one.  I only do it when the loco doesn't seem to run just right.  It does help.  I don't know why, but these capacitors don't seem to affect the running characteristics of all locos. 

The little yellow pills on the lower right are the capacitors on an older Bachmann loco:


I did clip these out and it really smoothed out the loco.

Both forms of capacitor are easy to remove.

These photos are taken with a cheap digital camera.  The images are loaded into photobucket and easy to copy and paste to a post once you've done it once.

Regards,

Jonathan

[richg]

Looking at the PC board pictures, a C prefix is a cap, a R is a resistor, a L is an inductor, a D is a diode. You can see what looks like two resistors. Those are two ferrite inductors. Some mistake them for resistors because they do not look for the L1 and L2 labels. Some have two wire wound inductors.
There are SMD inductors but I have yet to see them on Bachmann PC boards.

Photos in a question are much better than, my loco does not work. What is wrong with it?

Rich

[Tom M.]

For the newer style board shown in the top photo, I use what I like to call the blunt force trauma approach when installing a decoder.  That is, I cut the board apart between the screw mount hole on the left side of the photo and those large green "do hickeys."  That leaves me with the marked/identified solder pads showing the polarity of all the wiring circuits without having to worry about what component does what to what on the rest of the board.  I hardwire the decoder's power pickup and motor connections to the appropriate tabs on the remaining portion of the board.  I then make the lighting connections using resistor values more to my liking for the headlight and tender light.  This also ensures the decoder's motor control is not compromised by other components on the factory board.

This approach works extremely well for Tsunami sound installations.  Removing most of the board opens up room in the tender to install a large speaker and speaker enclosure, which provides excellent sound output.   

While this no longer makes for a plug and play decoder installation, it does remove any ambiguity of what does what on the board.

Tom

[CNE Runner]

RichG - Not being a person educated in electronics (although I am pretty good at plugging in a lamp) your post on capacitors peaked my interest. One of the reasons I 'left' the world of DCC was the requirement that all track had to be virtually spotless and electrically sound (insulated frogs causes havoc on small locomotives as an example). On my last DCC layout (some years ago) my Atlas MP15-DC would not simply use its flywheels to 'coast' over a problem spot (such as my Bachmann GE 45 Ton locomotive does in DC mode); but would stop and go through the 'start' procedure. A European buddy had mentioned that one of the decoder manufacturers (Lenz?) has capacitors(?) to eliminate this problem. If that is so, I have to wonder why other manufacturers don't follow suit?

Gosh, I hope I worded this correctly,
Ray

[jonathan]

Ray,

Other manufacturers do indeed install this capacitor.  I know Soundtraxx has one, and I believe some Digitrax decoders now offer this feature.  I think the nickname is a "Stay Alive" capacitor, which keeps the loco going very briefly over a trouble spot.  Like you, I'm not an electronics guy, just picked up this info as I went along, intalling my own decoders. 

I often wondered what that coffee-can-looking 'doohickey' was hanging off a couple of decoders I put in. 

Only problem is, now I have to run my Varney Li'l Joe around my layout to find potential problems.  Everything else has enough wheel pickup (or other doohickies) so I don't know the track is getting dirty or losing electrical continuity.

Regards,

Jonathan

[jward]

that "coffee can" is most likely an electrolytic capacitor, which is polarity sensitive and filled with oil. we exploded one in lab back in electronics school by putting it into a circuit  backwards. it made quite a bang and leaked oil on the board.

[richg]

RichG - Not being a person educated in electronics (although I am pretty good at plugging in a lamp) your post on capacitors peaked my interest. One of the reasons I 'left' the world of DCC was the requirement that all track had to be virtually spotless and electrically sound (insulated frogs causes havoc on small locomotives as an example). On my last DCC layout (some years ago) my Atlas MP15-DC would not simply use its flywheels to 'coast' over a problem spot (such as my Bachmann GE 45 Ton locomotive does in DC mode); but would stop and go through the 'start' procedure. A European buddy had mentioned that one of the decoder manufacturers (Lenz?) has capacitors(?) to eliminate this problem. If that is so, I have to wonder why other manufacturers don't follow suit?

Gosh, I hope I worded this correctly,
Ray

More about the Stay Alive issue than you probably care to know.

http://www.members.optusnet.com.au/mainnorth/alive.htm

Rich

[CNE Runner]

RichG - Thanks for the website link regarding the 'Stay Alive' feature of some decoders. I did read the entire 'article' and was only momentarily mesmerized...not that I had much of a clue as to the content. The chap was very thorough in his explanation for the process of adding a 'Stay Alive' capacitor to the decoder (trust me...you don't want me, and a soldering iron, anywhere near your decoder). I was most impressed by the ability of the Lenz sound decoder to continue running a diesel over a 12" piece of tape applied to the rails!

The web page author mentioned that some of the 'Stay Alive' capacitors weren't large enough to really do the job. If so, one has to wonder why the manufacturer didn't include a larger unit.

The 'Stay Alive' feature seems to be an excellent option for any sound decoder. Since my Bachmann GE 45 Ton locomotive is silent; it should have little problems with minor interruptions of power.

Thanks again,
Ray

[richg]

More capacitance, larger physical size for the cap. You can parallel capacitors also for more capacitance. There are practical limitations.

Rich