Thursday, 6 August 2015

DCC Update - from System/1 to NCE

For the last year I have had intermittent problems with my DCC system. Some locomotives have run away (no they were not analog capable), I have blown several frog juicers, and have had intermittent shorts that affected the whole layout rather than the circuit being protected. In between trains ran OK.
As well as these problems I also noted several locomotives running hot. I spent several "days" on the web and talking to colleagues. 
Finally one of my colleagues in the Sydney NMRA chapter (Lawrence Nagy) offered to come over and apply a second head to the problem. Lawrence arrived with his DCC manuals, and current power testing tools, including Multimeter We both experienced a short that occurred at a certain spot (on a certain switch frog). We thought the frog juicer was at fault and replaced it. We even replaced the switch. Changing the frog juicer fixed the problem. However Lawrence wasn't convinced that was the only issue.
Lawrence applied a current test with the Multimeter - looked OK. Then he checked the voltage on the track and WOW - it was 23 volts!. We followed testing across the wiring and discovered the System / 1 Command station was putting out 23 volts. We experimented with changing the voltage output by setting it for "G", "N", and "HO" scales. But the voltage stayed at 23 volts.
This is where the internet is powerful. A quick search showed this has occurred before to other users. I contacted the local NCE distributor, who was also aware of this issue, which was caused by the bridge rectifier on the Command Station main board failing. There was no fix other than replacing the main board in the Command Station.
Given my System / 1 was nearly 18 years old and had served me well I decided to cut my losses and replace it with NCE. I basically had an NCE system anyway as the command bus and all the controllers were already NCE. My circuit protectors were also mainly NCE. So all I had to do was buy an NCE PH-Power Pro unit. The System/1 had an automatic reversing circuit in it and I replaced this with another Dual Frog Juicer from Tam Valley. I had been using Dual Frog Juicers already for controlling the reversing circuits and had a spare unit anyway. They make a great auto reversing circuit. 
I also ordered a "RRampMeter" which reads current and voltage across the layout and can be moved to any area to also check for voltage drops - maybe due to weak wiring connections.
Installing the new system was easy and so far everything seems to be working fine. I did have to reset several of my locomotive decoders back to factory default and re program them. I use a SPROG 2 to record all the settings but given the previous systems were set using 23 volts, I played it safe and re programmed all decoders and recorded them on DecoderPro. DecoderPro is a JMRI tool that keeps all the settings on your computer, so if you ever need to reset a decoder you can just copy the settings using the SPROG2 to talk to the locomotive. 
Last April I presented on DCC wiring at the Australian N Scale / NMRA convention in Brisbane. This experience has enhanced my knowledge and personally added a few pointers that I should have been following and I think all DCC users should follow
These new / additional lessons are:
1. check voltage at each power district. Use a multimeter to do this. It is possible to have voltage drops from the booster or as I experienced a faulty Command station giving excessive voltage. Many command stations have adjustments for voltage to cater for different sizes of models. "G" scale requires a higher voltage than "N" scale for example. 
2. use a set of metal wheels to test all circuit units like Frog Juicers are working as designed to do. Run the wheels over a frog and see if the frog juicer or similar switch actually switches the polarity.
3. Also connect up a short detector as you connect every wire to the main bus. This will identify a fault on installation. Alan Gartner (Wiring for DCC) and others strongly recommend this but it is easy to let haste take over and connect a wire incorrectly.
4. If isolating the frog on switches, test the wiring and insulation before installing. I discovered one "properly" wired switch had some metal filings on top of the insulation and gap I had created, and this caused a small short.

DCC is terrific and really makes operation and general running more fun and realistic. But, it can come with issues. Following the basic rules for wiring should produce many years of reliable running.

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