Yes.........they are expensive ! With shipping and tax, I ended up paying the 100uF/20V at $1.65 a piece on eBay (and I got 8) I hope to be able to install 3 of them in my P42, so 300uF instead the 100uF from the stock decoder....
A few things about capacitors. Pick the voltage rating that is approximately twice the operating voltage. I would NEVER use a 16V cap for our 12V application. 20V would be minimum and even higher would be better. I understand that higher voltage rating can mean bigger in size, which is critical for our application. If you want to go cheap on the Bay I would burn them in when you get them. I would put a voltage on them for near their rated voltage and keep it there for a while. Note, do it on a non-flammable surface away from anything. I can bet you that a few may go pop and catch on fire. You don't want that happening while they are inside your loco. I would highly recommend getting the good stuff at places like Digi-Key and even then, burn them in. A few links were posted that shows "tantalum" and "tantalum polymer" (tantalum poly for short) capacitors. The polymers are definitely more resistive for failure so try to get those. Question for yourself is how much value is that loco shell to you versus a few dollars for a better cap?
I went ahead and picked up some 220 uf -- 20v... https://www.digikey.com/en/products...P66yAFaK5mW1LggWhZyRYVYQ6a4kVwgk6vNM2K3SUR39v and 100 uf -- 20v .... https://www.digikey.com/en/products...pg5DnN0MsXOV_mjgwrnr8EVzPzbMksMwy4ZKGsLwrHbD2 and a couple of the SP-1208 speakers also, so should be set. The expensive part will now be if I end up getting sound decoders to go with them. I think cost is always relative to wants and desires. We went shopping in a furniture store the other day far from home (first time in a year after getting our shots) and afterwards my wife was longing for her first cup of designer coffee as I call it. We went through a drive-by 'Joes' and she spent $7 on a cup and was in heaven. I went home and spent about 20 cents maybe on a cup of instant and was just as happy. I want tools and supplies to build things and have spent thousands of dollars on those things. I don't want or desire new cars so have saved thousands. Main thing is do what you can to be happy with what you can afford Sumner
Well, the ones I bought are +/-20% tolerance...(and Digikey are the same) So 20V @ +/-20% = 16V mini and 24V maxi Since I'm running my layout at 13V (voltage at the power supply, so less on the tracks)....I would not test them at 20V, but may be 16V (or 18V max) By the way, is it really a "burn in" or a quick test? Capacitors act as a short until they are charged, then no current will flow thru them. So keeping them under a specific voltage without charge/discharge....what does it do?
I would say the only thing I can't go cheap is Scotch (whisky)...........A good Islay + a good movie is sooooooo good !!!
The burn in is a good idea to get rid of the ones that would die early. These tantal caps do actually blow up, and supposedly create little clouds of smoke when they fail (enough to set off a nearby smoke detector). I don't think they would destroy a PC board, but locomotive shells are pretty thin. The max.voltage allowed is actually a bit higher than their nominal voltage, but then the continuous voltage allowed is again a bit lower (80%, I think, depending a bit on the actual voltage rating of the cap). Have a look at the digikey datasheets. I'm not sure how the nominal voltage of the DCC system relates to the voltage that the cap sees on the voltage 'rails' of a decoder. I think depending on how the DC conversion and ground referencing is done, you could get up to twice the DCC voltage.
