Scott Kay posted:Hi Pete,
The reason for my use of three KA2 Keep Alives is due to a test that I ran. Basically, it had to do with what it would take to not have to clean track. I had a test loop and I started out an cleaned the track thoroughly by hand wiping with alcohol and a paper towel. I then used the wiped finger test where no black residue was left on my finger so I knew the rail was clean. I then ran about a 10-car train around several laps and no flickering lights and then let it set, came back and ran the train again a month later, did the wiped finger test and noticed the black residue had returned. This was good though and actually what I wanted to see. I also noticed that the lights started flickering a bit, especially at slow speeds. I then installed a single Keep Alive and performance improved, no more flickering lights. I then let it set for another month, ran the train a bit, and then noticed the flickering lights had started again. So I added a second KA2 Keep Alive and the flickering lights went away again. It finally took three Keep Alives to get it to the point where I no longer had flicking lights or sound hiccups while still not cleaning track on these particular Atlas Dual Drive locos.
Now, I was nosing around the ESU Loksound and various ESU Loksound DCC retailer web sites (always a dangerous proposition) and I noticed that the Loksound XL 4.0 has a built in Power Pack (Keep Alive) that looks like it uses the exact same capacitors as those used on their upcoming Power Pack Maxi device so I’m thinking that it might end up being a wash to go with the Loksound XL 4.0 vs. Loksound Select L decoder with a Power Pack Maxi even though in some respects the XL 4.0 is a bit of overkill for O Scale. However… even with a street price just north of $200 for the XL 4.0 and a slightly larger size, you get more speaker handling capability with two independently balanceable channels, nice screw terminals (not the small solder pads), built-in keep alive that might be equivalent to the Power Pack Maxi (just guessing at this point), and all in a single package. Has anyone installed a Loksound Select XL 4.0 and does it truly have a noticeable extended keep alive capability for the larger scale?
Thanks.
Scott K.
Austin, TX
Thanks very much for the detailed reply Scott. Makes sense now. 
That is a big challenge to never have to clean your track again! I did similar cleaning stages with alcohol and then applied a very thin layer of graphite which I learned about on MRH and at my local club. I have not cleaned track in a year now and still no flickering lights or dropped sound. Of course there are several treatments that I'm sure work well, such as what Max suggested.
A couple of things I've heard about Loksound that might be relevant. Max, you're way ahead of me on Loksound so please chime in if I'm talking through my hat again! 
I think there's a CV to set what happens in the event of momentary power loss. You can have the motor go back to what is was doing, or stop, or something else. And you can have the sound go back to its previous state, or re-start, maybe something else. Not sure if having the motor go back to previous speed would alleviate the issue at all, compared to having it stop (if that's even a thing)?
Secondly (this is not about keep alive, but about XL 4.0), I believe the XL 4.0 does have larger keep alive built in, but didn't Max have trouble with the PWM drive frequencies not being compatible to some degree with China drives and at all with Pittman motors? Not sure if that would direct you back to the newer Select L.
Last thought I had was that your track seemed to get dirty very quickly i.e. a month later. Do you have any plastic wheelsets on your stock? The biggest single improvement in track cleanliness for me was when I switched to 100% metal wheelsets a few years ago.
Sadly I suspect that in the end, to run DCC flawlessly even with large keep alives may be a bit of a tall order without DCC friendly switches, powered frogs and clean track. If I were starting today I'd be looking hard at dead rail/battery power!
Pete
