# Bachmann DC DD40X Diesel Union Pacific horn sound repair



## Michaeld4502 (Feb 26, 2018)

I recently bought this loco 2nd hand. The loco runs, the blinking Led works and the light bulbs, but it has a horn sound and it doesn't work. 
Would anyone know how it supposed to work ? 
I suspect one the components on the "Space Age Electronics" on the PCB maybe faulty.
I connected 5VDC to horn and it makes a sound, just not while it's on track.


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## Bwells (Mar 30, 2014)

I'll give your thread a bump as I am interested in how this could be possible with DC. I would suggest going to the Bachmann website and their forum, "ask the Bachmann" and see if you can find something or pose a question.


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## Michaeld4502 (Feb 26, 2018)

*photos*

Here are some photos of the PCB. Is the yellow wire a signal wire ?


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## rickbz28 (Jan 10, 2016)

Have you tried putting batteries in it?


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## Michaeld4502 (Feb 26, 2018)

*Batts didn't help*

Yes I have tried with batteries, I am hoping someone else has or had this loco so I can find out how it is supposed to work.


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## CTValleyRR (Jul 26, 2014)

Do I properly assume from the information you originally posted that this loco was manufactured in 1981? If so, I wouldn't have much hope for it. Bachmann stuff manufactured before about 2005 is notoriously mediocre.

What are the battery leads for, if not to provide power to the horn? Is the loco battery powered, as opposed to track powered?


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## Michaeld4502 (Feb 26, 2018)

I guess that's my question how is it supposed to work and what is the purpose of the batteries ? On the track it moves and the led flashes. So much for "space age electronics".


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## wvgca (Jan 21, 2013)

what turns the horn on ?? whats the trigger button, or what ever ?


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## CTValleyRR (Jul 26, 2014)

Michaeld4502 said:


> I guess that's my question how is it supposed to work and what is the purpose of the batteries ? On the track it moves and the led flashes. So much for "space age electronics".


"Space age electronics" in the early 1980's looks a lot like stone knives and bearskins now. This is not a state-of-the-art item you have purchased.


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## Bwells (Mar 30, 2014)

Like Warren says, what is the trigger to activate the horn? The batteries must provide the power but there needs to be a way to turn it on. You mentioned with 5 volts it makes a sound. If the batteries are inserted does it honk and stop? The wires from the batteries run over the PCB and appear again at the speaker. Is there a component in one of the leads on the other side of the board? Maybe a magnetic reed switch activated by a specially placed magnet under the track? Just guesses here!


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## bluenavigator (Aug 30, 2015)

Actually, I own two Bachmann DD40AX myself. Neither have that horn at all. Seem that it was addon design? Really surprised to see that. By battery holder being there, i suspected that former owner have the layout down with something that triggers the horn when go over something on the track. I am pretty sure of that. Kader made the PCB and i do not see anything for horn...but I see C+ and C- (x2)and B+ and B-. Is the battery holder hooked up to these B-/+ on the PCB?


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## Michaeld4502 (Feb 26, 2018)

I don't know what the trigger is, my thought is it could be the yellow wire. Maybe when it reaches a certain voltage before the motor starts moving ?
With the batts installed there is no horn. I applied 5VDC directly to speaker/horn.
There is no component in the wiring, the red and black go from the pick ups via the circuit board to the motor. I'm going to have to check every component on the board, cause Now I want it to work!


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## Michaeld4502 (Feb 26, 2018)

bluenavigator said:


> Actually, I own two Bachmann DD40AX myself. Neither have that horn at all. Seem that it was addon design? Really surprised to see that. By battery holder being there, i suspected that former owner have the layout down with something that triggers the horn when go over something on the track. I am pretty sure of that. Kader made the PCB and i do not see anything for horn...but I see C+ and C- (x2)and B+ and B-. Is the battery holder hooked up to these B-/+ on the PCB?


The batts are connected to C+ & C-. I would like to see photos of your locos.


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## bluenavigator (Aug 30, 2015)

Here are photos of my Bachmann DD40AXs. As you can see that there is no buzzer or rear circuit to handle the buzzer. There is no yellow wire or battery holder at all. 




























I am suspecting that yours were modified, copying specific circuit from other Bachmann locomotives but which locomotive, no idea. I could be wrong as they could be removed from manufacturing, as being phased out. I got both of them from two different sellers on ebay. 

What I am going to do on mine, is to add second pancake motor to the front. I have several extra pancake motors. They were notorious to go bad. The reason why they go bad, it is because of shaft where it is being held inside both sides' holes, which are all plastic, no metal bushing to hold them in place. They were spinning, rubbing against the wall of the hole, causing them to be out of alignment then stopped as the rotor is hitting either side. Hope it makes sense. That's the reason why they were not being used anymore. Also, I am considering to convert them to use horizontal motors. It is just idea... nothing solid yet.


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## jason (Mar 19, 2021)

I know this is an old thread, but this is what you need to activate the horn. I had that dd40x and 2-10-4 Texas chugger with horns.


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