Keep alive for an Economi?

[Maletrain]

I recently bought an HO Bachmann Civil War type 4-4-0 with an Economi sound decoder in it.  It actually creeps nicely on my 6' of straight test track.  It has no trouble going all 6' at speed step 1 of 128 in reverse, but it will run smoothly and then suddenly stall a few times in 6' when going forward at speeds less than step 4.  All it takes is a slight jiggle of the track and it is off and running again, even at speed step 1. Both drivers have electrical pickup on both sides of the locomotive, and the tender has one 2-wheel truck with pickup on one side and the other truck with pickup on the other side.  No traction tires.  I have not (yet?) figured out exactly what the issue is with running slow forward.  There is still some cleaning and polishing of contact surfaces to do before I start looking for electrical enhancements.  But, I have some concerns about how this loco might handle the less-than-perfect track work at my club.

So, I thought I would ask now whether anybody here knows if there is a practical way to add a "keep alive" capacitor to an Economi decoder.  This particular decoder is Manufacturer 141 decoder version 082.

[Maletrain]

Well, I got no answers here, but I did eventually get an answer from SoundTraxx customer support.  Since I see a lot of views, here, I will provide what I learn so that others might use it, too.

So far, all I know is that the 082 version of the Econami is custom-built for Bachmann, so the tech wants a picture of the board so that he can tell me where to attach the wires for the keep alive.  So, he seems to be confident that it can be done, which is good to know.  I am going to run the loco on a layout with curves, grades and turnouts to know how it behaves right out of the box, before I take it apart.  But, that keeps getting delayed by other demands on my time and the layout's availability.  So, when I get to the point of having a picture with attachment points identified, I will post it here.

[peteski]

Keep-Alive is basically a large capacitance capacitor and some ancillary components. It needs to be hooked up at the output of a bridge rectifier on the decoder.
This pretty much applies to all mobile decoders (since they all share similar design for their power section).  If I had the decoder at-hand, there was an excellent chance I could very likely tell you where to hook the Keep-Alive. Looking at a photo should also work in many cases (but it is not as certain).  However if the instructions will come right from the proverbial horse's mouth, that will be even better. 

[woodone]

So is the 82 version a different decoder than a regular Econami that SoundTraxx makes for retail sales?
The normal Economi uses a capacitor hooked to the green/yellow stripped wire and the blue wire coming from the large connector that is plugged into the decoder. You just replace the 220uF cap with a current keeper.
I am guessing the 082 version is a special decoder made just for Bachmann  and does not have a plug in harness.

[Maletrain]

Before I made the original post, I searched the SoundTraxx documentation on-line to see if Econami decoders were designed to have keep alive capacitors added.  It turns out that there are several designs of the Econami boards, some with simple plug-in connectors for the SoundTraxx "Keep Alive" and some that require soldering.  My problem is that I can't tell, from the Decoder Pro readout of the decoder's version, which of the Econami decoder versions in the SoundTraxx documentation applies to what I have.  Apparently, the SoundTraxx technician doesn't know which document applies to "Version 082" either. 

I am really not clear on what "Version 082" applies to.  Is it the version of the whole board, or just the actual train control chip soldered to the board, which may be combined with different physical components on various boards in various configurations, as well as different "custom" programming for Bachmann, only?  I do know that the whistle sounds on my version do not match the SoundTraxx documentation for the Econami, so I am wary of making assumptions.

As I said, I will post what I learn, once I learn it.  But, there will be some delay in my getting to this.

[woodone]

Will be interesting to see what you end up with.
This has been a concern of mine when a manufacture uses a decoder supplied from a separate decoder manufacture.
They advertise has this loco has this (xyz) decoder but don’t tell you it was made to thier specifications, but is still referenced to a type of decoder, the decoder people make.
Now it (the decoder) is almost a priority decoder, the decoder manufactures can’t give you any specks because it is the loco’s manufactures decoder so to speak.
Now the loco’s manufacture really does not supply support because they don’t speak decoder information.

[jdcolombo]

Before I made the original post, I searched the SoundTraxx documentation on-line to see if Econami decoders were designed to have keep alive capacitors added.  It turns out that there are several designs of the Econami boards, some with simple plug-in connectors for the SoundTraxx "Keep Alive" and some that require soldering.  My problem is that I can't tell, from the Decoder Pro readout of the decoder's version, which of the Econami decoder versions in the SoundTraxx documentation applies to what I have.  Apparently, the SoundTraxx technician doesn't know which document applies to "Version 082" either. 

I am really not clear on what "Version 082" applies to.  Is it the version of the whole board, or just the actual train control chip soldered to the board, which may be combined with different physical components on various boards in various configurations, as well as different "custom" programming for Bachmann, only?  I do know that the whistle sounds on my version do not match the SoundTraxx documentation for the Econami, so I am wary of making assumptions.

As I said, I will post what I learn, once I learn it.  But, there will be some delay in my getting to this.

If you can post a high-rez photo of the board, we might be able to tell you how to add keep alive to it.  I think I have one of the Bachmann Economi decoders somewhere in my parts pile (I replaced them all with ESU LokSound decoders).  I'll see if I can find it.  A good chore for in-between bowl games!

John C.

[Maletrain]

OK, I ran the train for a while on the club layout, and it performed well pulling 4 passenger cars.  I made sure it did not run below speed step 4, and had no problems with it stalling.  But, I still want to see if I can install a "keep alive"/"current keeper" to make it capable of crawling reliably.

I took the shell off the tender and exposed the board.  It does not have the on-board socket for the Soundtraxx current keeper.  It does not have a Soundtrax identifier, but does have "Bachmann 4-4-0, Rev A" printed on the bottom.  See the second photo, below for what is printed on it.

Except for the red wire coming from the right rail, all wires are black.  That is not much help in following the Soundtraxx instructions for installing their current keeper, because those instructions are worded for color coded wires.  The Soundtraxx instructions are to solder the blue wire from the current keeper to the blue wire from the decoder, and the black wire from the current keeper to the "green/yellow striped wire" or "the black decoder capacitor wire" depending on which model of decoder is being used.  Since this is possibly yet another model of decoder, I have no confidence in figuring out which of the many black wires on this decoder goes to the current keeper black wire.

Here is a picture of the top of the decoder:

[ Guests cannot view attachments ]

and the bottom:

[ Guests cannot view attachments ]

Thoughts? 

[peteski]

These 4 diodes are the bridge rectifier which takes the DCC signal and converts it into the DC voltage on the decoder.
The blue pads (and any copper areas connected to them) are the positive side (12V or whatever the track voltage is minus about 1.4V).
The yellow-green pads (and any copper areas connected to them) are the common or "ground".
Attaching the keep-alive to those pads should produce the desired result.

Next photo is strictly speculative - you need to verify whether I'm correct!



If you have a ohmmeter (multimeter), then check whether the yellow-green pads are connected to the yellow-green pads on these 2 capacitors, and whether the blue pads on the bottom are connected to the blue pads of the capacitors.  If they are connected (zero ohm resistance between them) then you can attach the keep-alive circuit to those capacitor pads instead of needing to solder on the bottom of the board.

Those two 100uF 25V capacitors seem to be connected in parallel. They are a likely candidate for what would be a small on-board keep-alive circuit. But it is just my speculation at this point until you can verify it.  Of that pair of capacitors is not connected to the output of the bridge rectifier, then they obviously serve a different purpose.

[Maletrain]

Peteski, Thanks for the very helpful response.

At this point, I have verified that the caps are connected in parallel, but am having trouble getting resistance readings on the connections between the diodes and caps.  I need to make some smaller probe tips for my multimeter to do stuff like this, because I  am not getting reproduceable measurements for resistance, or even continuity between the caps and diodes.

But, if it does pan out that the current keeper can be connected across those caps on the top of the decoder board, that will be a lot easier to do than the approaches described in the Soundtraxx manuals.  So, I will be pursuing that idea as I ask questions of Bachmann and Soundtraxx.

I will post what I find out.

[peteski]

The negative side of the caps will almost certainly be connected to the negative output from the bridge rectifier. But it might be possible that there is another diode between the positive output of the bridge rectifier, and the positive side of those 2 large caps (ESU decoders use that type of design). It could be one of the diodes marked "74" near the caps. But then those caps are only utilized for the decoder's electronics (the microcontroller and the audio circuitry). Motor driver still likely gets its power from the bridge rectifier directly (or through a low-ohm resistor).  If you attach the keep-alive directly to the bridge rectifier output (as I indicated), should work correctly.

I'm curious as to where the Soundtraxx manual tells you to attach the keep-alive circuit?

[Maletrain]

...
I'm curious as to where the Soundtraxx manual tells you to attach the keep-alive circuit?

Well, here's a link to the directions on their website: https://soundtraxx.com/content/Reference/Documentation/Reference-Documents/currentkeeper-pkgincert.pdf .  As you can see, it isn't talking about the economi version that I have in this Bachmann loco.

I am sending the pictures of my decoder to a guy at Soundtraxx.  I also hope to talk to a Soundtraxx rep in Springfield.

[peteski]

Well, here's a link to the directions on their website: https://soundtraxx.com/content/Reference/Documentation/Reference-Documents/currentkeeper-pkgincert.pdf .  As you can see, it isn't talking about the economi version that I have in this Bachmann loco.

I am sending the pictures of my decoder to a guy at Soundtraxx.  I also hope to talk to a Soundtraxx rep in Springfield.

You right - that document is not helpful (since it doesn't show your decoder). But looking at where they attach the keep-alive on the other decoders, I feel it is pretty safe to connect it to the bridge rectifier output.  But I'm also curious what Soundtraxx says.   Hey, I'll be at Springfield both days - maybe we can meet in-person?

[Maletrain]

PM sent.

[Maletrain]

OK, Here's the Soundtraxx advice:

[ Guests cannot view attachments ]

So, they are saying what you are saying, which is to attach it to the output of the rectifier, blue wire to + and black wire to -.  That makes sense, but is on the bottom of the board.  I am going to have to study soldering techniques to improve my chances of not screwing this up.  I don't want to kill those diodes trying to solder to those tiny SMD pads right on them.  I also should figure some way of making a strain relief for those wires.

At this point, I am not sure where the actual keep alive caps will be placed.  The remaining room in the tender shell, above the board, is about 1" wide, by 5/8" long by 1/8" high.  The "current keeper" is much bigger than that.  If I don't find another option that will fit in the tender, my plan is to run the wires from the board to an external plug on the tender chassis, then have a wire with a mating plug coming out of the RPO car behind the tender, with the keep alive in the RPO.  Unfortunately, Athearn glued the roof onto the body of that RPO.  But, I can unscrew the weight from the bottom of the RPO and cut through the plastic floor to insert a keep alive.