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Discussion Starter · #1 ·
I have a number of O scale MTH 3-rail diesel locomotives but know nothing about them.
I am not sure if they are original 3-rail or have been converted to 2 rail (how do I tell).
there is a plug hanging out the back, what would this be for?
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Also power supply, should this be AC? I have ordered a MTH Z750 which is AC output.
I have added a couple of pictures of one loco.
any help would be great
thank you in advance
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That one is three rail and does not have command control. Conventional only assuming it has not been upgraded. I believe most MTH 2 rail diesels come with fixed pilots. Someone added that tether for some reason. They didn’t come that way.

Pete
 

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Looks like the pickup has something screwed in to hold it up so that it does not contact the center rail. The tether may be to run a smoke unit or lights in a trailing unit. Can't tell what's been done to that loco. A peek inside might help.
 

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My only 2 cents concerns the wheels. I'd get a dremel tool with a wire wheel at the end for cleaning them....they sure look rusty, and as such, they wouldn't make very good electrical contact. I agree that the tether is a strange addition...probably NOT OEM!
 

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You are going to have to open the shell. That loco- especially with that 3 wire connector that someone installed, and also the 3rd rail pickup rollers look like a special standoff has been used to lock it up out of the way.

Seeing those modifications it's anyone's guess what we might see on the inside.
 

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The PC board likely has a rectifier on it to run the DC motors on AC. From the pic, it's a close match (but not exact) to one of the Williams electronic E-units (but it's not). The tether could be motor power to a second loco for double heading, or, the module's sound output to a trailing car with a speaker. A couple of switches are wired in. Perhaps reverse lockout and sound on-off.

A pic of the PC module's top would be helpful.
 

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Could this have been possibly converted to be a slave unit tethered to another engine?

You said you have a number of locos. Do you have another one with the three color futaba wire that would connect to this one?
 

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Discussion Starter · #12 ·
thank you once again.
not sure what the PC module looks like to take picture.
do you think this would be DC or AC?
I have 8 locos but not checked any others.
 

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The gents with the experience have spoken ...

How about this module in the loco.

View attachment 585377
Appears to be a common CV (Constant Voltage) board for lighting. Nothing more than a diode and capacitor, maybe a 780X series regulator frame mounted for heatsinking.
Given, this was an MTH engine, those are common on PS1 engines- but as you can see clearly, someone stripped this of all but the smoke unit and that board.
 

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Right here, this topic highlights a problem I talk about on occasion.
Modifying an engine is all fun and games for you the owner and operator. The instant someone else has that modified engine and has to work or it or even figure out how to operate, there is no manual, no diagram, no instructions. Shining example of creating a disaster for the next person who has to touch that engine.

I'm as guilty as anyone, I have a few engines modified- and one day someone will likely be cursing, who the heck did this???!!!

My personal favorite, the yellow wires to nowhere.
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Then you have the "spark plug" or "suicide plug". They are just likely connecting the lights, maybe to that regulator board but that is an accident waiting to happen and let some smoke and bad smell out if that shorts or touches anything else.
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Discussion Starter · #20 ·
this is great information many thanks.
I used a gaugemaster controller (DC) and just touched the centre pickup and a wheel and motor ran.
there is a speaker which i removed from the base but it was not connected to anything.
 
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