Zimo mx649N fitting stay alive

[Phil Mackin]

Hi all

I picked up a Zimo mx649N cheap with a Valenta sound file. 

I took the 6 pins off and soldered an 8 pin plug as I'm using it on a OO hst. 

Question is how can I fit a stay alive?

I've put a Lais across Common positive and ground but it isn't working. 

I've trawled through all the Zimo instructions I can find but I can't find a wiring diagram for this particular decoder. 

If anyone can help me I'd be very grateful

Cheers Phil 

[Nigelcliffe]

The diagram for the MX649 is on page 12 of the Zimo MX manuals English version.  

 

Common positive and ground are next to each other, at the opposite end to the track feed, motor output, etc..    

 

 

[Phil Mackin]

Thanks Nigel 

I have actually connected to the Common positive and ground but I can't get it to work 

Could it be something to do with a cv I need to change perhaps? 

I think from what I have read Railcom being switched off could be a possibility 

Cheers Phil 

[Nigelcliffe]

I don't think there is any need to change CVs.  I've never changed any in all the Zimo's I've done, though I don't recall doing a MX649.     I've fitted a number of the other smaller Zimo sound decoders, such as MX648, MX658, etc.  with the Lais stay-alive module.   They have RailCom enabled (because we use it on some layouts).

 

Check you really are onto the decoder positive and ground.  Without the stay-alive you should be seeing just below track voltage across those two pins. 

 

And, check the stay-alive is working.   A quick test-rig for a stay-alive is just a small motor would do, apply approx 10v to motor with stay-alive connected across the motor, wait half a minute, then disconnect the 10v supply volts.  The motor should continue to run for a fair period of time. 

 

 

 

 

[Phil Mackin]

Certain I'm on the right solder pads, I had to use the blue common for the directional lighting which works perfectly (I presume that the 6 pin PCBs have built in rectification as they don't use the common connection). 

I've tried 3 different stay alives so I'm at a loss. 

I'll check Railcom is on and rewire it just in case 

Appreciate your help 👍 

[Nigelcliffe]

If you're certain its the correct pad, and have measured the voltage, then I can't say what is the issue.  Three stay-alives are unlikely to be faulty, again assuming correct wiring (pos-to-pos, 0v-to-0v).  

 

6-pin locos use one side of the pickup as the "common positive".  That gives half-wave common positive, because half the time it's negative so current doesn't flow through the lights.   (Standard stuff, in the manuals, you can do this DIY to save a blue wire to the decoder ). 

[Phil Mackin]

Nigel 

I disconnected the blue wire I foolishly connected thinking I needed it for the lights to work correctly and bingo it works perfectly now. 

The only down side is that the lights go out on the stay alive but the sound and motor keep running for ages. 

I can't imagine why the addiction of the blue common to the 8 pin plug stopped it working but all is well now

Cheers again Phil 

[Nigelcliffe]

No idea what's going on, but wonder if there's something odd about your loco's wiring.   It is clearly getting common positive from the rails as the lights work, and then go out when pickup fails (stay-alive takes over).   

 

- Nigel