TCS decoders (N-scale) Keep-Alive questions

[nickelplate759]

I like the little TCS decoders, like the M1 and M4.  I note that they support the addition of Keep-Alive capacitors, and can even be ordered pre-wired for them. That's nice.  I want to try adding a Keep-Alive of some sort - never done that.

The TCS pre-made Keep-Alives claim to be able to power an N-scale locomotive for 6+ seconds.  That's way more than I think I need.  I just want something that will cover up a small glitch in power-pickup - 1 second is plenty.  6 seconds seems way too long.

I assume I can just use some other appropriate capacitors, rather than the pre-made TCS Keep-Alives.  So here are my questions:
1. Am I right - I can just use a different capacitor?
2. Am I right - the TCS Keep-Alives are more powerful than I would need?
3. how much capacitance is enough?

[peteski]

George, I recommend reading this info.
The "keep-alive" circuits use Super Caps and they are in the rage of several hundred thousands of micro Farads.  We (modelers, including me) often misuse the keep-alive term for stay-alive circuits, usually home-brewed using tantalum caps, which have capacitance of less than thousand micro Farads.  Those stay-alive circuits have often been described in threads on TRW.  These stay-alive circuits don't supply energy to keep the morel running for more than fraction of a second, but they do greatly improve the running quality of the model during very short power dropouts.

These smaller stay-alive circuits are usually adequate for keeping the sound-decoder-equipped model running smoothly.  The best examples of adding such circuit to a decoder are in the Zimo decoder manual (towards the end of it).  While the manual is for Zimo, the info is applicable to other decoders.  Manual is attached to this post - see page 57 on.  In most of the stay-alive examples documented on TRW the capacitance is less than 1000 micro Farads (usually around 500).

This link should also be useful.


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[nickelplate759]

Great information, thank you!

[nickelplate759]

A naive question:  I have acquired a TCS KA4.   It's sort of a cube shaped - the 4 capacitors standing next to each other like 4 beer cans.  It fits fine in some N scale tenders, but NOT in a Bachmann USRA tender (any size) because of the space taken up by the circuit board in the tender.   I don't want to remove the circuit board since it's part of the tender pickup.   

Is it a reasonable project to disassemble the KA4 (it has 4 capacitors in it, maybe some other stuff) and re-wire it so that the capacitors are side by side - in a 1x4 row?  This would allow it to sit on top of the circuit board.

I don't want the end result blowing up, either in my face or in the tender, and I really don't know much about what I'm doing here.

[peteski]

Yes, if you have the skill to do it quickly and cleanly, you can remove the caps from the PC board and wire them to be remote from the board.
Those are likely low-voltage (2.7V or 5V) Super Caps and they are likely wired in series on the board.  If that is the case, you coudl just wire them the same way off-board, then run only the 2 leads form the ends of series chain to the appropriate pads on the PC board.

Or maybe use TCS KA2?  That one has 5 small caps placed horizontally on the PC board.  It is 1.3" long, 0.45" wide, and 0.34" high.

[nickelplate759]

Those dimensions seem to be from the old KA2 that was discontinued.   TCS has announced a new, smaller one, but there's not much information on the TCS website yet.  It looks promising in their video.   Thanks!

[peteski]

Those dimensions seem to be from the old KA2 that was discontinued.   TCS has announced a new, smaller one, but there's not much information on the TCS website yet.  It looks promising in their video.   Thanks!

Ah, I didn't know.  Mine was purchased several years ago.