How do I add DCC to a Spectrum GP 30 Diesel?

[jeffHOtrainCO]

I acquired a Bachmann Spectrum GP 30 Diesel Union Pacific #731 and would like to add DCC to it as that is the direction I am going for my permanent track build.  I am pretty technical, I just can't seem to figure out what decoder I need for this loco.  Thanks.

[jward]

Is this the one with the split frame? If so, whatever decoder will fit will work. It is a relatively simple hardwire. This applies for any locomotive using the split frame design. I used Digitrax DH123 or DH163 decoders for the job, due to them being shrink wrapped and thus insulated from the frame.

There used to be an online tutorial done by one of the former members of this forum, who has unfortunately passed away.

Here is how it is done. WIth this design, the frame consists of two halves, insulated from each other, that sandwich the drive components. It does, however, require a complete disassembly of the locomotive.  The trucks conduct electricity to the frame halves by contacts that rub the bottom of the frame. It is not necessary to eliminate these, they are fine the way they are. The motor has two tabs connected to the brush caps that contact the frame halves. You must remove the caps, being careful not to lose the brush springs, cut off the tabs, and solder the motor leads from the decoder to these caps. Be sure to insulate them so they cannot contact the frame halves. Once you have done this, reassemble the locomotive,. The decoder should have enough room to ride on top of the frame  just under the roof of the body shell.

The frame halves are held together with a plastic T nut assembly, with a spacer washer keeping the frame halves insulated. As they come from the factory, the T nuts both face the same way. When reassembling the locomotive, you must reverse one of the t nuts. The track power leads of the decoder are tucked behind the T nuts, which hold them against the appropriate frame half. tighten everything down, and checque for shorts with an ohm meter before you power everything up. If it passes this test, you are good to go.

I have done about a dozen locomotives this way.

[rich1998]

I just check the Digitrax site Both are discontinued if I saw correctly.
Look at the Digitrax Selector page. A 1 amp small decoder with no plug will work.

I have used a DZ125 in a Bachmann loco, 0-6-0, which is upgraded to a DZ126, Good for HO and 1 amp. I just checked.
Order Kapton tape at the same time. Thin and tough. Forget black electrical tape.

Rich

[jward]

The 0-6-0 is also a split frame design. I've also done a couple of these using the DZ125. It's the only thing that fits. I removed the smoke unit and put the decoder in the cavity.

The DH123 and 163 are discontinued but upgraded versions are still available. Digitrax has a very orderly system for naming their decoders and once you understand it, you can easily find the upgraded versions.

DH123= Decoder, HO, 1 amp, 2 function, version 3.

DZ125- Decoder, Z scale, 1 amp, 2 function, version 5.

there are often letters in addition to these that denote the wiring harness. One advantage of Digitrax decoders is that the HO decoders utilize a standard JST plug on the decoder itself. They come with your choice of interchangeable wiring harness, for hardwired (Short and long harnesses) and NMRA 8 pin socket. This modular construction means that if you have a decoder go bad you simply unplug it and plug in its replacement, even if the harness is hardwired.

[jeffHOtrainCO]

I found a DH123D on Ebay, will that work?

[rich1998]

Yes.e small decoders are nice. Just no BEMF but not an issue for some.
Below are the specs.. If you have to hard wire, just follow the decoder instructions. That is what I did when I started.
If the loco has LED's, use 1k, 1/4 watt resistors. Isolate the two motor leads. For a light bulb loco, some use a 22 ohm resistor, 1/2 watt. The voltage surge is what can blow a light bulb. Many replace with an LED.

https://www.digitrax.com/products/retired/mobile-decoders/dh123d/

Rich

[jeffHOtrainCO]

Thanks! I ordered the ones from Ebay, a 2 pack so we'll see how they work!!

[rich1998]

These small Digitrax are ok.
As I said before, I had the DZ125 and DZ126. No connectors. Z, N and HO scale. Good for one amp.
Not much bigger than a dime. Even ran a Pancake motor in a 0-6-0 loco. I like experimenting.

Rich

[rich1998]

I just looked at the parts page for your loco.
If it is a DCC ready, it has an eight pin socket. Ready to plug in a decoder.
Hopefully the decoders come with an eight pin plug or you will have to buy a couple from an online store.
The socket should have pin one marked.
This shows a DCC ready PC board with DC adapter in place and LED's.

Have you taken the shell off?

https://estore.bachmanntrains.com/index.php?main_page=popup_image&pID=7865

Rich

[rich1998]

Diagram ifr you do not have it. Diagrams come with new locos.

https://www.bachmanntrains.com/home-usa/dwg/dwgs/60801.pdf

Go to the Parts page and look for the loco under HO. You can see all the parts that are sometimes available.

Rich

[jward]

I just looked at the parts page for your loco.
If it is a DCC ready, it has an eight pin socket. Ready to plug in a decoder.
Hopefully the decoders come with an eight pin plug or you will have to buy a couple from an online store.
The socket should have pin one marked.
This shows a DCC ready PC board with DC adapter in place and LED's.

Have you taken the shell off?

https://estore.bachmanntrains.com/index.php?main_page=popup_image&pID=7865

Rich

SPectrum GP. 30s were released around 1988 or 1989. They were not DCC ready. You're thinking of the later standard line version, which comes both DCC on board, and DCC ready. Different design.

[jeffHOtrainCO]

Rich, no it doesn't but I found a you tube showing how to solder this decoder on, looks pretty straight forward. The DH123D. I'll post an update once I get it done.

[rich1998]

Ok. Use a pencil iron. Not a soldering gun. I suspect you know this.
I did not look up the loco so had no idea how old you loco was.
I also get shrink from a local hardware store if I need it. No electrical tape. Messy.
Some times I use a small piece of piece of PC board as a tie point. Any little trick to make it easier. Bath caulk to mount the PC board but other adhesive works, Double sided foam tape.
I have quite the junk box.

Good luck.

Rich

[jeffHOtrainCO]

Rich,

I have pencil solder, kapton tape and shrink wrap on order as well, along with a with a flux pen, helping hands and precision wire stripper. I have a couple other locos that I want to convert so hopefully this one goes well then I can move on to those.

[rich1998]

You should not have any issues. I never did. Just follow the wiring diagram on the decoder instructions.
I always use the program track, FIRST.  That will usually tell you everything is ok.

Rich