Lenz Silver Mini problem

[danmk1]

Wondering if anyone could advise?

I have installed a Lenz Silver into a Union Mills Loco and last night all was running well. However I am now stuck as today it has refused to do anything.

I can communicate with the decoder via JMRI but noticed CV30 was showing 4. I could not see any shorts and during the day have removed it from the loco and the motor runs fine, powered via DC. Have also linked the chip up, to a rolling road without the motor, to see if it still communicate, which it does, but is still showing CV30 as 4. I have tried to write it to 0 and am unable to carry out a system reset as it won't let me change CV8 to 33, but have also tried with my NCE control direct and this does reset the chip.

Being new to DCC I am wondering if I have a fault chip or a faulty operator.

Thanks in advance.

Dan

 

[Nigelcliffe]

You could have a faulty loco, or at least a loco fault which only shows itself on DCC.   Don't rule that out yet. 

 

CV30=4 implies a motor short circuit.   There are two types of these, either the internal wiring of the motor is at fault, or there is a current path from motor terminals to the chassis pickups (seen that happen several times, and with cheaper decoders that's bye-bye-decoder time).    Or, there is a possibility that the internals of the decoder have shorted, but the decoder sees it as a motor short.    In theory, you can clear the report of a short by writing 0 to CV30. 

 

CV8 will always READ the value of the manufacturer ID.   So, whilst you can write a value to cause a reset, it doesn't change the value you can read back. 

 

 

Diagnosis from where you are -

1)  Try the decoder in another loco, or at least with a motor rigged up to its motor output leads to see if it works following a reset.   If it doesn't work, then the chip is blown.  But, you need to find out why it blew, they don't generally blow randomly. 

2)  If you have a multimeter, check that there are no paths from motor wires to the pickups of the loco.  If either side shows a path, then that's your fault and it must be corrected. 

3)  When refitting any decoder into this loco (or any other), you should put the PowerCab into Programming Track mode (first), and only then place the loco on the track and attempt to read a CV.     If you can't reliably read CV values back, there is a fault in the loco / installation that needs correcting BEFORE you attempt to give it track power. 

[danmk1]

You could have a faulty loco, or at least a loco fault which only shows itself on DCC.   Don't rule that out yet. 

 

CV30=4 implies a motor short circuit.   There are two types of these, either the internal wiring of the motor is at fault, or there is a current path from motor terminals to the chassis pickups (seen that happen several times, and with cheaper decoders that's bye-bye-decoder time).    Or, there is a possibility that the internals of the decoder have shorted, but the decoder sees it as a motor short.    In theory, you can clear the report of a short by writing 0 to CV30. 

 

CV8 will always READ the value of the manufacturer ID.   So, whilst you can write a value to cause a reset, it doesn't change the value you can read back. 

 

 

Diagnosis from where you are -

1)  Try the decoder in another loco, or at least with a motor rigged up to its motor output leads to see if it works following a reset.   If it doesn't work, then the chip is blown.  But, you need to find out why it blew, they don't generally blow randomly. 

2)  If you have a multimeter, check that there are no paths from motor wires to the pickups of the loco.  If either side shows a path, then that's your fault and it must be corrected. 

3)  When refitting any decoder into this loco (or any other), you should put the PowerCab into Programming Track mode (first), and only then place the loco on the track and attempt to read a CV.     If you can't reliably read CV values back, there is a fault in the loco / installation that needs correcting BEFORE you attempt to give it track power. 

 

Thanks Nigel for coming to my aid, again. 

 

Have tried the decoder just by itself as shown.

but still get CV30 as 4 after a reset.

Had checked the wiring when on the loco and had no shorts from motor wires to pickups so will assume that the decoder is at fault but am at a loss for the cause of blowing.

As well as the rolling road I have a little test loop, for a programming track, which I use before putting them onto the main track.

[Nigelcliffe]

I can't diagnose any more from the information available.   You need to put a motor load on the outputs to get any sense out of the decoder.   But, from the information available, it looks like a failed decoder.  Cause of failure unknown. 

 

 

In terms of programming tracks - the CRITICAL bit is that a programming track is unpowered for 99.9% of the time, there are only tiny programming pulses when programming.  The tiny programming pulses are limited in power, so you can program (and also confirm installation), but not sufficient power to damage components.    So, a "rolling road" or a "little loop" are NOT programming tracks, as they are places where track power can be applied !

The PowerCab has a significant shortcoming in this area.  Because it only has one output, there is track power on that until you switch into programming track mode and it removes power from the track.   My recommendation is to purchase the NCE auto-switch (well under £20) which goes on the PowerCab's output, and gives you two connections, one to layout, one to programming track.  That provides better protection of testing installations on the programming track. 

 

 

- Nigel