Zimo MX634 and TCS KA2 stay alive (or not)

[Torper]

I've had a TCS KA2 stay alive for some time but haven't really known what to do with it.  However, in view of recent posts and a discussion with a retailer I decided to link the KA2 to a Zimo MX634 I was installing in a loco I'm building.  The Zimo has two wires (blue and grey) specifically to be fitted to a capacitor, so I duly connected the blue wire on the Zimo to the blue wire on the KA2 and the aoppropriate grey wire on the Zimo to the other wire on the KA2.  Rather to my disappointment, this has made no difference whatever to the running of the loco; although I've given the KA2 plenty of time to charge up it still stops at dead bits on the track, and it still won't start off again at one point where the rails are dirty.  It did that before I fitted the KA2 and it does it just the same after fitting the KA2.  It therefore seems clear that the KA2 isn't working.

 

So what am I doing wrong?  Should I adjust a CV to take account of the KA2?  Are the Zimo and the KA2 truly compatible?  Have I got a duff KA2 (though it's difficult to see how something so relatively simple could be duff).  The Zimo works well, just the same with the KA2 as without it.

 

Any help would be appreciated.

 

DT

[norman]

I've had a TCS KA2 stay alive for some time but haven't really known what to do with it.  However, in view of recent posts and a discussion with a retailer I decided to link the KA2 to a Zimo MX634 I was installing in a loco I'm building.  The Zimo has two wires (blue and grey) specifically to be fitted to a capacitor, so I duly connected the blue wire on the Zimo to the blue wire on the KA2 and the aoppropriate grey wire on the Zimo to the other wire on the KA2.  Rather to my disappointment, this has made no difference whatever to the running of the loco; although I've given the KA2 plenty of time to charge up it still stops at dead bits on the track, and it still won't start off again at one point where the rails are dirty.  It did that before I fitted the KA2 and it does it just the same after fitting the KA2.  It therefore seems clear that the KA2 isn't working.

 

So what am I doing wrong?  Should I adjust a CV to take account of the KA2?  Are the Zimo and the KA2 truly compatible?  Have I got a duff KA2 (though it's difficult to see how something so relatively simple could be duff).  The Zimo works well, just the same with the KA2 as without it.

 

Any help would be appreciated.

 

DT

Hi DT

Assuming your connections are good. The KA2 wires are blue and striped black/white. Connect blue to blue and grey to B/W

Then check the value in CV153.  

This CV is used to control the stay alive feature it sets the time in 1/10 second the loco will continue without signal.  

The default is 0 which is the same as 255 maximum.

regards

Norman

[Torper]

The KA2 has a lot of capacity (5 x 1F 2.7v supercaps, about 200,000uf)) - enough to power a loco for up to 15 seconds.  The loco draws no more that 0.11 amps, usually much less.  I would therefore expect the KA2 to power the loco quite happily over the few small not-so-clean spots on my test track.  It doesn't.  I take your point that dirty track will prevent a loco receiving a command (I hadn't considered that before) but in this instance I'm trying the KA2 because pickup is from only two wheels on each side and I thought that a little bit of help might not go amiss.

 

CV153 was set to its default, 0.  I have now tried it with a number of other settings.  No change.

 

I think the problem must be the KA2  The connections all seem correct. Moreover, I have remembered that i did once use the KA2 before (unsuccessfully, albeit with a completely different problem!) and then I could hear a distinct whine when it charged up.  I hear no such whine now and suspect that it is not charging up.  Too late now, but tomorrow I will check all the connections more thoroughly.

 

DT

Edited August 23, 2017 by Torper

[Nigelcliffe]

When I've used KA2's on Zimo decoders, I've wired them to decoder positive (blue) and decoder ground (a solder pad on the decoder).  This by-passes the "charge/discharge" components fitted to most recent Zimo decoders because the same charge/discharge stuff is included in the KA device.

 

DC running needs turning off (CV29), and optionally the run-time on DC (capacitor) needs to be set to limit how long the loco runs without a DCC signal (stops it driving over the embankment and onto the floor). 

 

Some consideration of layout track voltage is needed.  The TCS KA device is rated at about 16v track voltage.  From the components I've inspected inside one, there is precious little headroom on the components for any more volts, and I'd expect it to fail if over-volted.   Its probably happier if the track voltage is a few volts lower - say 14v. 

 

 

A KA2 should run a 4mm scale loco for a stupid distance, it does in my installations. 

 

 

- Nigel

[Torper]

Thanks Nigel and others.

 

I've had the multimeter out and been doing some testing.  I first tested the KA2 to see if there was current continuity through it.  There was.

 

Track voltage is 13.8v AC, and the mutimeter showed that that is getting to tthe decoder (as indeed it must as the loco works).  Now I've always assumed as the only connection from/to the KA2 is by the blue and black/white wires which I've connected to the designated blue and grey wires on the decoder, these wires carry current to the KA2 for storage and then presumably carry it back again when required.  However, according to the multimeter there is no output at all from the decoder to the KA2 which presumably acounts for the fact that the KA2 isn't charging up.  So  it looks as though it's the decoder that may be at fault.  I might therefore try to cut away a bit of the plastic sheathing on the decoder to check that the blue and grey wires are connected (from what I can see through the sheathing they seem to be), or I may just fit some additional pickups to the loco's pony wheels.

 

DT

[Izzy]

I wouldn't mind betting that one or both of the wires have come adrift under the sheath after the recent issues I have had with some Zimo MX600's. I bought four, two of which (unbelievably) turned out to be duds - quickly tested and replaced by the dealer - while the other two original ones keep having their wires coming adrift under the sheathing. Not easy to re-attach because it's a single sided board with the wires soldered in layers under the sheath, which has to be cut back to gain access.

 

Izzy