This site has a good summary of keep alive information:
http://www.members.optusnet.com.au/mainnorth/alive.htm
You may find it helpful in your efforts. From my limited knowledge of KA caps is that you can't simply replace a small cap with a larger one without changing some of the circuitry that feeds the "recharge" current into that capacitor.
You might get too much inrush current, or not enough to fully "charge" the capacitor.
I followed Selector's recommendation and removed all my Blueline decoders. Eventually I'll get around to some of my other QSI's too.
The capacitor that BLI uses should be enough to keep the sound from cutting out during short interruptions. If the sound is cutting out but the motor decoder doesn't, there could be a problem with the board or the speaker.
Good Luck, Ed
I can't imagine that it would hurt, unless the wrong cap were applied. However, if I had a BlueLine whose sound was acting up, and I couldn't fix it easily with cleaner tires and wipers, I would seriously consider just taking out that rigging altogether and using a proper sound decoder such as the Wow, new Tsunami, or probably the spiffiest one out there now, LokSound. I have several QSI Titan and Revolution decoders, all excellent, but I think QSI is on the rocks.
I have a Blue line with a TCS T-1 motor decoder..runs great...no stop and gos. My sound still glitches...I'm thinking of putting a TCS KA on the sound decoder...just solder the KA wires on to the leads from the electrolytic cap that's already there. TCS thought it would work but have no testimonials. Any thoughts before I bite the bullet. Thks. in advance.