Trouble with locos fitted with Zimo decoders

[petertg]

Hi all!

Here I am again with questions for which I ought to know the answers. I have two very old Lima H0 locomotives (mentioned before in this and other places) which I need to preserve because, if I scrap them, I will have to scrap also a substantial amount of goods and passenger rolling stock.

These questions are directed mainly to users of Zimo decoders. Although you will probably consider me long-winded, I must explain the background. When I purchased my first Zimo decoder (MX632) I downloaded the instruction manual but, since it is 80 pages long, I only printed out the last 10/11 pages which contain a summary of the Cvs. I had also downloaded and printed DCC Concepts advice and, since the material of interest was contained on some 5 pages, it was more manageable than a leaflet of 80 pages.

I purchased a second MX632 and fitted it to my Lima CC 40101 (SNCF loco) and, with the default settings of the decoder I put it on the main track and it worked perfectly. I then fiddled with the CVs based on the DCC Concepts information on the assumption that the CVs of all decoders were the same, but I have now discovered (the hard way) that they are not (I had not read that he said the specific decoder manual should be consulted). As a result, the loco started to suffer from spontaneous energizing and running away uncontrolled when I powered up the controller. This problem was solved by doing a reset but I now have another problem (with two decoders, since I fitted yet another MX632 to my other Lima H0 loco). I can read and program the decoders, so I must assume that they are correctly installed (proof of this is that the first one did work well for a time).

The problem is that I place them on the main track and the lights switch on correctly but, as soon as I move the controller to speed step 1, they cut out (in less than the 20 seconds mentioned below). For further information, I am using a 16V AC transformer and my controller provides a track voltage of 22·5V. According to the manual, the MX632 decoder is said to accept up to 50V track voltage and withstand a peak motor current of 2·5A for 20 seconds. Can anyone suggest what I should do to get these locomotives to run well?

[Nigelcliffe]

1 turn the track voltage down a bit. 22v is far too high for HO/OO locos. Suggest 18v max, ideally less.

 

2 follow the motor tuning steps in the Zimo manuals. It might be long, but much of it won't be needed as it covers advanced sound and lighting features.

[shibushe]

I have never had problems with Zimo Decoders. However it does seem to me and has Nigel says voltage is to high. Far to high.

The Zimo manual is very complex, containing CVs that the basic user of DCC would NEVER use.

As for DCC Concepts information for DCC, its ok for having a read just to see how DCC works. But not to follow it as gospel.

The decoder instructions are the first place to refer to, as you say not all manufacturers use the same CV for the same result.

They must conform to the rules   by the NMRA. So if you compare the Zimo manual V TCS you will see this is so, or any other manual

I would suggest you lower that voltage not below 12v . 2nd. reset the decoder to default 3.

Run this loco with out any other CV settings see what happens.

[Edwin_m]

How are you measuring 22.5V?  Remember that most meters on AC setting will give incorrect readings for DCC track voltages.  Easiest way is probably to measure the DC voltage on an activated function wire (relative to the blue wire) and add about 1.5V. 

[petertg]

I haven't tried testing the track voltage any other way but, after much testing, I tried upping the start voltage and it seems to work, although I have set it too high, since the loco starts like an EMU, namely too fast. I suppose that it is a question of trial and error until I find the right point.