Digitrax Soundbug capacitor

[AustraliaJim]

Can someone please tell me if the capacitor with the Digitrax Soundbug is a keep alive capacitor?

If it is, could I remove it and install a larger one?

I'm fitting this into a loco that already has DCC motor control and I have plenty of space in the tender.

Thanks

 

Jim

[Stevert]

Yes it is, and yes you can.

Just keep in mind that if you do increase it's size (capacitance), you may also increase your risk of encountering the "inrush" issues that other sound decoders are notorious for.  Not a showstopper, just something to be aware of.

[MisterBeasley]

Do you feel that you need a larger capacitor?  If the loco is getting pickup from all the wheels, including the tender, you shouldn't have any need for a keep-alive capacitor as you should never lose power.

[AustraliaJim]

Thanks guys, I might try it without adding a larger capacitor first.

One question though. How do you avoid "inrush" if you use a bigger capacitor?

Thanks

Jim

[Stevert]

AustraliaJim

One question though. How do you avoid "inrush" if you use a bigger capacitor?

You can add a diode and a resistor.  There is a diagram how it's done on this page.  Scroll about halfway down the page to the section titled "My loco stalls on turnouts or doesn't run smoothly  I want to add a keep alive capacitor." 

That diagram shows an additional capacitor being added, but the principle is the same if you're just replacing the existing capacitor with a larger one.

[MisterBeasley]

If you decide to put in a larger capacitor, check the one that's installed and mark which lead is plus and which is minus.  I think they use electrolytic capacitors, which must be installed with the correct polarity.  As I recall, they don't color-code the wires, so mark before you snip.

[rrinker]

 If you want to simulate the Youtube video where the GE loco has a crankcase explosion just as it passes the guy filming, hook the capacitor up backwards. Yes they are electrolytics and they pop quite impressively if hooked up backwards.

 Also I believe th Digitrax sound decoders may already have the diode and reistor for preventing inrush, since they don't have a problem with this in normal operation (and program just fine on a normal program track withno boosters). 5 cetns of parts that SOundtraxx and QSI could add and never have an issue - but there's more profit in selling program track boosters I guess.

                           --Randy

 

[AustraliaJim]

Thanks for pointing me in the right direction Guys. Thanks for the link Stevert, very informative.

Cheers

Jim