Author Topic: Wiring help Needed on Loco with 21 Pin Plug  (Read 15296 times)

KB02

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Wiring help Needed on Loco with 21 Pin Plug
« on: October 18, 2022, 08:58:49 PM »
The last of my locos to be converted to Railpro and finish my conversion from DCC is my Rivarossi U25c. This loco has a mother board with a 21 pin plug on it. For ease of installation, I purchased the TSC 21 to 9 pin adapter. Simple enough install - plug and play, so to speak, for the main functions and sound, but the extra two accessory (function) wires coming from the 6 pin plug on the LMS3 are giving me trouble.

Here is a picture of the TCS adapter I am using:

The wires go straight to the 9pin plug and are the standard colors. Everything here works fine. Blue if the universal +, white wire to headlight, yellow to rear light, green wire to function 1 (F1), purple wire to function 2 (F2). As you can see it also has solder pads for F3 through F6, speaker, Ground and Cam (cam, I am assuming for a chuff cam on a steam loco).
This particular loco has front and rear lights, number plate lights and two sets of emergency lights - red and white, front and rear.
The number plate lights are connected to 9pin green wire (F1), the front white emergency light is connected to 9 pin purple (F2), the rear white emergency light to F3, front red to F4 and rear red to F5.

I know the circuits work as I have connected them with jumper wires just to test functionality, but for the life of my I cannot seem to get the purple of green wires from LM-S3 6 pins harness to power up any of the lights when connected to the F3, 4, 5 or 6 pads.
What am I missing?
I tried connecting the yellow wire from the 6 pin harness to the ground pad on the adapter, but still saw no success. Any suggestions?

CPRail

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Re: Wiring help Needed on Loco with 21 Pin Plug
« Reply #1 on: October 19, 2022, 08:32:21 AM »
Hi KR02,

On the few 21 pin installs I've done, only the wires/functions from the 9 pin side work through the harness and they've covered my needs.

On the 6 pin side, I only use the speaker wires and the yellow wire (one half of the Keep-Alive wiring). From the RailPro instructions with the LM-3S, it looks like you need to wire directly from 6 pin wires (and the blue common on the 9 pin side) to whatever lighting option you are hooking up.

I haven't done a lot of installs needing more lights. The only engine that I'd be wanting to do that in is a Rapido SW1200RS, and there's not a lot of room to work with there. I had enough "fun" just getting the LM-3S, the speaker and the Keep-Alive in! One of these days...

I'm sure some of the more advanced installers here can provide more detailed info.
Ian Lisakowski
Modelling CP Rail & VIA in the early 80's

KB02

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Re: Wiring help Needed on Loco with 21 Pin Plug
« Reply #2 on: October 19, 2022, 05:02:04 PM »
Yeah, the LM-3s instruction sheet is a little less than helpful in this case.
All the other locos that I have used the 6 pin leads for have worked fine. I'm going to have to do a little more testing to verify that the leads are good coming out of the LM. That should have been a first step, but, oh well...

CPRail

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Re: Wiring help Needed on Loco with 21 Pin Plug
« Reply #3 on: October 20, 2022, 09:32:00 AM »
Alas, you are now past my limited level of knowledge. Most time I'm happy to get the loco to run and to get sound.

These electronic doodads are still mysterious things. I know that as long as you keep the magic smoke inside of them, they work. Let out the magic smoke and they stop working!  ;D
Ian Lisakowski
Modelling CP Rail & VIA in the early 80's

KB02

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Re: Wiring help Needed on Loco with 21 Pin Plug
« Reply #4 on: October 24, 2022, 06:08:52 AM »
I figured out my problem. The realization came while I had given up and was bypassing the Rivarossi MB and installing little jumpers:
- The Loco has more lights and function options than a standard 9 pin decoder can drive, and more than 6 functions than the RailPro LM can handle. Thus, if we put our logic to work, there wouldn't be a direct connection from the decoder to the lights as everything beyond the standard functions of the 9 pin decoder have to go through logic circuitry in the motherboard and are controlled by CV programming in a DCC decoder.
- No CV's, no direct control of the lights.

So, a couple of jumpers and an extra resistor and I was back in business... almost...
In my testing of everthing jus to make sure all my lights and leads worked, I ended up frying the headlight LED (Grrrr....). I've got the part number, now I's a matter of finding somewhere to get one from.