Early Soundtraxx and Keep Alive problem

[kenkal]

I’m having trouble with an early Soundtraxx DSD-LL100LC. It’s just a PCB with holes for connections – no cable, no shrink wrap. Has anyone installed a Keep Alive or Current Keeper with one of these?  

 

I called Soundtraxx for where to put the connections.  Justin sent me an e-mail JPG showing  the black lead connected to a hole next to a corner electrolytic and near a speaker connection.  The other lead is to be connected to a hole on the other side of the board labeled +5 volts.  Loco runs fine, sound effects are normal. But the Keep Alive doesn’t seem to be working.  When I shut off the power the sound instantly shuts down and the motor likewise instantly stops.  The other Keep Alives’ I have installed keep the sound going for about 20 seconds after I shut it down.  The motor would keep running if I hadn’t stopped it. I checked the connections and the soldering and everything seems fine. The KA is the new TCS KA4.

 

I tried the internet and this forum to no avail.  Any help would be greatly appreciated.  

 

Thank you. Ken

[gmpullman]

Hi, Ken

See if this site will help you.

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

I believe there is a photo of a DSD-100 there.

Good Luck, Ed

[kenkal]

Yup, the 100 is there but unfortunately not the LL100 which is totally different in shape and connection points. 

Thank you though, for suggesting it, Ed.  Ken

[gmpullman]

The only other ray of hope I can offer is that I had the very same situation with an Econami Steam decoder with a CurrentKeeper.

Similar situation, sound and motor control all good. I found a few CVs that were supposed to be changed for the CurrentKeeper to work but that still made no improvement.

Then I did a "Factory Reset" using JMRI and the CurrentKeeper came alive after that! Been working ever since and has one of the best KA performances keeping the engine moving and sound on for almost 20 seconds after cutting rail power!

Of course your decoder was made well before KA was developed, still, should be no problem. I just wondered if a reset might help.

Good Luck, Ed

[rrinker]

The usual connection for a keep alive is the positive common (blue wire) and the negative (which is going to be on the board, the negative side of the bridge rectifier). Since the keep alives are designed for 15V or so, if it's getting charged from a +5 connection it's not going to get enough energy to run anything, 5V is probably below the threshold even for the sound part of it.

 I don;t have one to look at, but it sounds as if that negative terminal of the capacitor is a valid spot for the circuit common. I'm not sure why they would tell you to hook to a +5V pad instead of the blue wire for the positive leads - is there another pad next to the one they said that maybe you got mixed up what they were pointing to? Since that decoder was made for P2K locos it may have two function commoons, one limited to work with the stock light bulbs and one at full voltage for use with your own resistors and LEDs.

                              --Randy

 

[richg1998]

Is this it?

I would just connect to the output of the full wave bridge.

https://www.walthers.com/plug-play-decoders-dsd-ll100lc-for-life-like-emd-e-units

Rich

[DigitalGriffin]

On the LC's the capacitor was used for the speaker to control the low bass output.  (cheap hi-pass filter)   So that cap lead would be a less than ideal spot.  It wasn't until the Tsunami 1 that the capacitor was used for a small power backup.  

[kenkal]

I'll give that a try. Thanks for the suggestion, Ed. Ken

[kenkal]

The instructions specifically said +5 pad and pointed to it. I wondered about it not being the blue wire as well. I think I'll try the blue wire. But I'll need to trace the common to make sure it's out of the bridge and not just for the sound amp. Thanks for the thoughts, Randy. Ken

[kenkal]

Yeah, that's the one as mine looks exactly like it. Hopefully I can identify the bridge negative and give that a try too. Thanks for responding, Rich. Ken

[richg1998]

Glad to help. Actually quite an easy search.

Track the traces from where the DCC comes in from the pickups. The opposite side with be the output for 12 to 14 vdc.

Visual or with an ohm meter. I have used an Optivisor. For viewing.

I just viewed the picture and expanded it quite a lot. I see what looks like two 100ufd, 25 volt caps. Cannot see what the underside looks like though.

Does not look to difficult an issue.

The cathodes for the diodes are marked and the minus side of the capacitors are marked.

Rich

[rrinker]

 Notice it has the exact same red and blue component between each pair of rectifier diodes just like the LC model shown on Marcus' site. That tells me the have the same input rectifier circuit, it's just on the side instead of the end, and you would wire a keep alive the exact same way as Marcus shows.

 I was wondering what that component was, since in at least one of the examples Marcus has the keep alive hooked right across it, implying one side if the positive rail and the other is the negative rail. Well, it's a Zener diode which makes me wonder why those old Soundtraxx decoders were smoked by too high a DCC voltage (Atls/Lenz Commander was notorious for more than 20V on the rails when the Zener would serve to clamp the output of the bridge rectifier to whatever the Zener rating was. Of course, go too far over the Zener voltage and the Zener itself might fry which then could let the overvoltage get to the rest of the decoder and blowing that, too.

                  --Randy

 

[kenkal]

Rich, I followed your visual look and it worked out very well. Easy to trace as you said. Unfortunately, the loco ran for almost 1/2 hour before it just up and died. I checked the mfd date and it was July of 2000 -- almost 17years old! I suspect some component just died of old age (I hadn't run it for maybe 5 or 6 years because the sound would keep restarting on track issues). Not too upset because it was my first decoder and the only one like it that I had. Thanks to everyone for trying to help. Much appreciated. Ken