MTH Premier Santa Fe Hudson MUX Board Issues (20-3144-1)

I didn’t watch your video, ….it was taking too long to load,…..but, if you wiggled the harness near the mux and things began to work again…..suspect a cold solder joint on the pins of the mux, …if you have a steady hand, and good soldering practices, should be an easy fix….also look at the harnesses for pushed out female pins, etc,…

Pat

Thanks for the advice Pat, I have both a steady hand and a very decent soldering iron, I will try and rework a few joints. You may be correct, I had not thought of that possibility. Thanks!

I had the day off yesterday due to the storm but I'm in South Florida and it seems mother nature was on our side and we are back to normal today. I will update you tonight.

Thanks again!

Well, I got home, cracked open an adult beverage, and reflowed the larger MUX pins. I don't have the skills to redo the IC but I didn't see the pins move as I picked them a bit. Reinstalled and that did nothing. So I decided to safely poke and prod a bit to see if I can find what could be wrong and discovered a bit of voodoo magic. @gunrunnerjohn posted this diagram back in Jan 2021:

Thanks for this John, I was able to determine what was what with this diagram but I am confused as to what that "MUX" wire should have voltage-wise. I see it even goes to the tender, which I just had taken apart as this loco was sold to me with some battery-related rust issues so it is possible I missed a wire in the tender.

I'm close to finding the issue just need a boost from my fellow train family.

Thanks!

Darn, forgot to post the video of the new phenomenon.

The mux line has a logic level on it.  The fact that you're touching it and changing things tells me a likely suspect is the contact on that wire.  You need a new contact and a crimp tool, but you can steal a contact from an unused harness if you have one and splice the wire.

@gunrunnerjohn and @harmonyards you guys are definitely great soundboards. I got off the laptop, had dinner and after the girls went to bed I thought, let's follow the bread crumb trail, shall we? Took out my meter and went to town before the Dolphins come on in a bit, yes I am a masochist and have spent 30+ years of my life screaming at a screen on most football Sundays.

Care to guess what pin of the 10 does not tone across the tether? If you guessed the gray MUX wire you flipping win!!

So please tell me, is this tether is something readily available, or do I have to sit through a few MacGyver seasons to prepare myself for the surgery ahead?

Photo of tether for reference.

P.s. It is a pleasure to have stepped away for three years and still have guys like you all here to help.

What's the connector on the right end look like, a closeup please.

Hey John!

Your wish is my command.

On another note, gotta clip my nails!

Can you measure that tether in MM’s ?….this one is available at mthpartsandsales.com …..230mm long ….10 position 90 degree to 10 position straight ….

Pat

Hey Pat,

It measures 320mm long or 12.5 imperials +/-.

Took a look and it does not seem to come up at MTH's parts site, might have to get the 230mm open you sent and make it longer IF need be. The harness in the tender has a lot of slack so it is extremely possible the 230mm would work w/o modification.

I will wait till the morning to see if you gurus find an longer option (((Suppressing Thats what she said jokes))) and if not then what you sent above will work, I have done much worse with thinner wire.

Thanks gents!

@Daniel J. Gonzalez posted:

Hey Pat,

It measures 320mm long or 12.5 imperials +/-.

Took a look and it does not seem to come up at MTH's parts site, might have to get the 230mm open you sent and make it longer IF need be. The harness in the tender has a lot of slack so it is extremely possible the 230mm would work w/o modification.

I will wait till the morning to see if you gurus find an longer option (((Suppressing Thats what she said jokes))) and if not then what you sent above will work, I have done much worse with thinner wire.

Thanks gents!

Push come to shove, relocate the female receptacle in the tender so it’s closer to the front of the tender……I want to say it’s facing straight up in that engine. Perhaps turning it to run parallel with the tender floor will gain you the extra length needed …….I’d move the receptacle before I cut the tether up only to find out the dead pin follows you …..

Pat  

The tether Pat linked above will work fine. Just clip some wire ties and move the harness around. There's plenty of slack. I've got one with an identical harness (3463) and have used the above tether in it no problem.

I appreciate the help, guys.

A new part has been ordered and now we wait....

I will keep you all posted when the new part comes in.

Thanks again!

I found the same one yesterday, wanted to wait until I saw for sure the other end was the female connector.  There is also a male to female version.

If 5V was not coming across from the tender you would not have smoke fan or tach control.  Run away engine. G

@GGG posted:

If 5V was not coming across from the tender you would not have smoke fan or tach control.  Run away engine. G

Hey GGG,

You know, I read enough about the Proto2 steamers that I indeed feared the same but I can guarantee you that smoke worked and the engine ran like a top when she was together, I even tried to ignore the lack of lights because she ran so well, my OCD got the best of me and I had to fix her and have everything perfect. When the new tether comes we will see what occurs. Unfortunately, I got an email from MTH that our friend Ian made it so they could not ship my order so I hope this week that changes.

Thanks!

The wiring is pretty standard,  when tracing this down symptom drive what I am looking for.  You can take tender and enigne shell off and plug in harness.  Trace for continuity from the harness connections in the tender to the pcb on back of engine.  Gray 5V, blue PCB ground and Purple HL signal from the Tender MUX are the must haves to the engine mux for lights to work, and also smoke and tach.  So if they were good, it is not the tender harness but rather the wires from the engine pcb up to the shell/engine MUX.  Can't be any other way.  The mux also get Yel/Wht motor lead from engine side to generate PV on the mux for lights and smoke heat.  Many wire joints and connections between engine PCB and the engine mux, and plenty from mux to the features.  G

Hello guys,

Wanted to give everyone an update. The tether came in and I plugged everything in on my temporary track. It was indeed the tether as my meter confirmed on my last test.

Shot a little video to show it all working again.

What is odd is that smoke worked and as GGG says that should not have been the case. I posted a video of the engine at a crawl and smoke working originally.

This engine belonged to the late great Barry and maybe he experienced similar issues and rigged the smoke unit and speed control, not sure though, this engine was sold to me in rough shape. In any case I am happy with the outcome and help.

https://photos.app.goo.gl/XSmq3Y3aULqdfrrb8

As always thank you all!