With an 8 pin connector, if you have a first start up problem- IS IT THE PLUG-OR THE DECODER? Hard wire and do a good job, you are 100 % sure it's not the plug- On the installs that I do, the first thing to go is the OEM light board with the plug socket.For your lights using led's is a good idea, they will last a lot longer than a bulb. 3MM will work for you. You need to use the blue wire to the positive lead of the LED with a resistor-(1K will work) in line- hook the white-or yellow to the other lead of the LED. You must use a resistor on each LED.
I use the 8 pin NMRA connector exclusively on almost every locomotive, makes DCC life much easier. When I bought some Digitrax decoders that came with 9 pin JST connectors I wired them into a pair of Model Power E7s and to save space on four MDC Shays. My other 66 locomotives are 8 pin.I sorta standardized on warm white 3mm LEDs, I still have a few locomotives using incandescent bulbs.Mel Modeling the early to mid 1950s SP in HO scale since 1951
My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
DCC-ready locomotives are easily converted to DCC with the NMRA 8 pin plug on the mobile decoder. Some say it is better to remove all factory installed wiring etc. and hardwire the decoder directly. My question: "what is gained by hardwiring over use of NMRA plug?"
In my DCC novice understanding, the NMRA plug was developed for several reasons for consistency across manufacturers and to make conversion easy for the user (very important given differences in knowledge, soldering experience, and willingness to take on the project). Also, the NMRA plug makes it easy to switch decoders if one wants to upgrade or needs to replace a faulty decoder.
Hardwiring ensures that all connections are made correctly and eliminates splices within individual wires. It does take more time and careful work to ensure good solder joints and soldering correct wire to the appropriate location.
All of my locomotives are DCC ready and easy conversions to mobile DCC. Sound is possible requires milling the weight for a couple of them. As a novice, is it worth effort to go full hardwire?
Electrical connections are pretty straight forward but there is one that I am unsure how to do. Probably very easy once ya know! Front and rear headlights have a white or yellow wire connected plus the blue common wire. Not sure how to solder the blue wire. Is there a common wire from each headlamp and both soldered to the blue wire connector on the decoder (assuming flat, uncovered decoder)? Does not seem right given that decoders can have four or more light functions connected to the common. And what about decoders that have a jst harness with 9 wires coming from the decoder. How does one t-splice in multiple light function connections to the common wire (look like t-splices in wiring diagrams)? Hopefully, my question makes sense, I'm a DCC novice so...
Final question, my P2k locomotives have 1.5 volt bulbs that sit in a channel and project light out through a light tube. I want to replace these bulbs with LED's and mount the LED to the channel rather than to the locomotive shell. What size LED? 3mm is a common size I see mentioned but that is about 1/2 the size of the existing bulb. Should I use 3 mm or move up to 5 mm?
Thanks!