QSI Quantum Decoder Replacement in Sunset Models 2-6-0 SP Mogul

Model Railroader Electronics and DCC
1

Before I say anything else, I know I am in over my head. To my defense though, I have previously completed several successful DCC Decoder Installations/Replacements (Bachmann Spectrum 4-6-0, Athearn/Roundhouse 2-6-0, GE 45-tonner). This one seems to be a bit more complex, to put it mildly.

As mentioned in a separate post here, I own a Sunset Models 2-6-0 Mogul with a Quantum Sound Decoder that decided to act up. The Engine is shown in the first picture without its tender. You will see its tender later on opened up.

Sunset SP Mogul 2-6-0 (Engine)

After trying the suggestions made in my previous thread to get that decoder working again with no success, I recently decided to change the decoder. Since I have other Soundtraxx decoders and am happy with them, I purchased a TSU-1100. I was (and am still) planning to hardwire it.

I opened up the tender yesterday in order to complete the swap, and pulled out the decoder for replacement. Apparently, DCC standards were developed in order so that they can be NOT followed … Nothing in how the original decoder is laid out or was installed follows any kind of standard color coding, connection points are not labeled, and I cannot locate a schematic of the decoder that would indicate what each connection is anywhere online. And the company is out of business …

The first picture shows the decoder, with labeled connections, the second picture shows it as it was wired up with all connections.

Sunset SP Mogul 2-6-0 (Decoder) [url=https://www.flickr.com/photos/150

2

Urs,

I have done two of these installs - TSUs into recent Sunset 2-6-0s. The factory wiring is a bit frustrating!! In both cases I gutted the internal connections just leaving the pin connect to the loco in place and traced the track power connections with a volt meter to the loco. Track power was easy. Then I used low voltage leads to find the motor pairs by powering the pairs of wires until the motor moved (low voltage 1.3 volts – don’t blow anything up!!) that gave me the headlight pair as well. You will then have to test the headlight leads for polarity - use low voltage - not sure if there is a resistor in the line (don’t rember at this point)

You might ask on some SP forums for more specific info.

These are great runners and they look good. Good luck with the project,

Guy

3

Thanks for your response, Guy.

Yes, the factory wiring is very frustrating, since no DCC wiring conventions whatsoever are adhered to. Fortunately, other than the wiring, this tender is a dream come true in terms of space for a decoder!

So, if I get your answer right, it seems to confirm that my speculation is correct, the 6 wires are two each for Track Power, Motor and Headlight. You then just went through the leads trial and error, starting with finding track power, until you got lucky and found the correct pairs (with the headlight leads being the final result of the two previous eliminations).

For the tail light, there was a resistor in the line, but I am not going to make any assumptions re: headlight.

The final question then that I have is were you able to identify what the plastic encapsulated item is, shown in my 4th picture, located on the same plug as the headlights?. I am assuming I won’t need that for my Tsunami installation, but am curious what it could be. Will try to post a picture later.

You are right, this is agreat looking engine, and it was agreat runner before the decoder went south.

Again, thanks for your help

Urs

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That is likely the magnetic reset switch for the decoder. QSI used these a lot. You won’t need it for a Tsunami or TCS Wow.

Joe

5

Urs,

Yep just trial and error to find the correct leads for the motor and lights. I think Joe has it right on the reed switch thing. I just removed the boards and never looked back so I never tracked it down any further…

BTW: I started using the 2 amp Tsunamis wherever I have room for them as I never have to worry about amp draw (I still measure it and often replace high draw motors) Also no worries about brass drivetrains freezing and blowing up the decoder as they used to with the old 750s…

Good luck on the project.

Guy

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Thanks again, Guy, and Joe for your input on the Reed Switch (and confirmation I won’t have to bother with it, not sure what it actually does in conjunction with the decoder).

Following Guy’s instructions, I figured out last night where each of the leads goes to, and I will post a diagram here for reference. The bulbs appear to be low voltage incandescent (1.5V/15ma), so I will make sure I put an appropriate resistor in line.

I also took up your idea of the 2amp Tsunami, and ordered one. I will use the 1amp version I have on hand for another engine (I have a Proto 0-6-0 without sound). While that will delay the project slightly, I think that is a more robust solution. And I have not run this engine for over a year, who cares about another week or two. Plenty of other projects around. Will post pictures when this one is finished.

Urs

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Urs,

Glad to be of help. Looking forward to the picures of the finished project.

Guy

8

The reed switch is used with QSI to reset the decoder. You won;t need that with a Tsunami.

Since the lights are incandescent, polarity of the functions won’t matter.

If you have a multimeter with a continuity function, you have all you need to figure this out.

First, the track pickups. The ones fromt he loco MUST be in parallel witht he ones fromt he tender, it couldn’t work any other way. Since you know which 2 pins are the pikcups from the tender, start there with one of those, and see which one of the 6 pins used on the connector have continutity. That will be the pickup from the loco for the same side. Repeat with the other tender pickup side, only now you have only 5 possible pins to test. Now you know which 2 wires from the loco are the track pickups, and which side the go to.

ANother one you can figure out is the function common (blue wire in NMRA standard color codes). Since you know which two wires go to the tender light, one has to be the common, which will also go to the loco, and one has to be the function for reverse light (yellow wire in the standard). Try your continuity from one of the tender light pins to one of the remaining 4 pins. If one of them works, you have found the function common (blue) wire. If not, repeat using the other tender light pin.

You now have identified track pickup and the function common. For the rest, you will have to cut the connector off from the loco, you need wires (unless you have some very fine probes) and you will need a 9V battery, or a low voltage DC source. Put the loco upside down in a cradle, or on roller stands - we’re going to make the motor turn.

Take any two of the remaining 3 wires, and touch them to the battery. If the motor turns, note which way, forward or backwards. If forward, the positive terminal of the battery is on what should go to the orange wire in a standard decoder. If backwards, the negative terminal of the battery is on what

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Urs,

can you point me to the link with your wiring diagram for the connections to the loco?

replacing my dead quantum with a tsu-2200…

thanks,

-todd

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Hi Todd

I never was able to locate a wiring diagram, and followed the suggestions by Guy and Randy to identify each lead. They are pretty fool proof, the only thing you need to be really careful about is the headlight, since you don’t want to bust that.

I will check tonight at home if I took some additional pictures during the installation, once I had everything located and determined what needs to go where. I ended up using a TSU 2200 also, vs the 1100 that I had planned to use, and the engine runs beautifully now.

Will drop another note if I find the pictures.

Urs

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Thank you for this thread, Urs, as I need to get a DCC decoder installed in my Sunset Mogul. Did you happen to note which wires went where on the TSU 2200? Hopefully I’m not too late to the party here. Regards,

Mark Drury