Large Scale Central

Onboard battery/RC in a USAT GP38

Those of you that have done onboard battery/RC in a USAT GP38, post up what you used please, pics if you have them. I picked up a nice used Santa Fe yesterday at the show, even has a nice sound system in it, not sure what brand of sound board till I open her up later today. I am dead rail, so onboard battery is a must(I absolutely hate trailing battery cars). I want everything self contained in the locomotive. I will be removing the smoke units, its not realistic in my opinion anyways. Thanks Mike the Aspie

Wanted to add, I have a RCS palm size controller that I use for my live steamer that will also work for battery RC with the proper receiver/decoder. But its a basic model so no ability to sound the horn or bell if this sound board has that. Need to see whats under the hood of the GP38. There is only a small micro toggle on the fuel tank to raise/lower the volume. I am open to other 2.4ghz RC controllers if someone has a used set up that needs a home. Mike the Aspie


Most diesel units like the 38 have plenty of room for most installs.

I put the speaker in the fuel tank, and depending on the board sizes I can mount then inside the frame under the fuel tank. The batteries I hot glue or silicone under the fan blades to try and enclose the shell as much as possible.

I’ve done the old RCS elite system installs with Sierra Sound and now lately I’ve been ripping that all out and replacing with ESU Loksound decoder plus Martin Saint’s Blue Ridge Engineering Protothrottle adapter boards. As long as you know and are comfortable soldering heat shrinking wires they are both easy installs. Just go slow and take you time.

Here are pics of the sound board, the backup sound battery, which is dead at the moment from lack of use. Sound board and speaker are nicely installed in the fuel tank, backup battery inside the loco shell. Is this a Phoenix system, an early one? It does have 2 pickups in the fuel tank to sense track magnets for horn and bell trigger. Can I make those RC triggered or is this older set up just magnetic triggered? I have most of the track power pickups eliminated, just have 2 remaining wires to each truck that go to the truck journal pickups. The shoes and internal pickup wires are eliminated to isolate things. Mike

Trying to do this with minimal extra $$ spent. I have a 2 channel RCS control that is DSM2, so it can run any Spectrum or cheap DSM2 receiver. I have speed controls for RC cars that can feed the motors power. Just need a battery that will fit in the shell. I have a smart charger, so I can handle the charging port. As long as I know the batteries mah and number of cells, I can program the charger for it(its not an automatic one, I have to chose the battery type, cell count and Mah). I can live with magnet triggered horn and bell for now and upgrade to a better hand held controller in the future. Just want to get her on the rails asap right now.

I would also like to stick to Nimh battery power or Lith/ion and NO Lipos I do not want something that requries more than a single charging port on the locomotive like I use with my Nimh powered locos I have done previously (but they lack RC and sound, so bigger battery for this one in the 14.4v range, 3000+mah range).

Mike, to minimize $$ I make my own battery packs using 18650 LiIon in holders and protection boards. Here’s the basic setup:

I have a 2 channel RCS control that is DSM2

I’m curious if it is 2-channel. Usually the ‘bind’ button can trigger a channel when it is not doing the bind thing?

And if you have a center-off ESC that does forward/reverse on just one channel, then the 2nd channel can support trigger functions using Tony’s little relay boards. I do bells and whistles with them just be twisting the knob.

I have speed controls for RC cars that can feed the motors power.

I found most r/c car ESCs don’t reverse. I’ve been using Tony’s Cobra, but he’s now retrenching and saying buy them from Fosworks in the UK. He might have some left, and the Aus$ is still way down.

Here are pics of the sound board, the backup sound battery, which is dead at the moment from lack of use. Sound board and speaker are nicely installed in the fuel tank

That’s a Soundtraxx Sierra. Yes, junk the lead-acid battery (carefully.) For battery operation you will need an opto-isolator, which Soundtraxx used to sell (I still have a kit for one somewhere.) Let me know if you need the manual.

I guess we all have our preferences on what system we want to use and what we think works best for us. I use the RailPro system which you only need a the Hand Controller HC-2, note here you can just use the computer interface module which is around $35.00 and save the price of the HC-2 at around $300, but this does require using the computer to run your engines. A LM-3S-G module, a charging wiring harness, Lith/ion battery in the 3.5 14.4 amp range, a speaker. I personally take out all the factory electronics and pitch them aside, including all the lighting if it is not LED’s, just not worth dealing with old style lights. I also like the AirWire System, but the cost of RailPro per engine is less and much more compact to deal with. I use RCS of New England for all my RailPro needs, Don Sweet will work with you and his prices are good. RCS wiring harness will give you one charging port for the battery charger and one switch that you can switch from run to charge, which is about as simple as you can get. RCS will also have a module stand offs for the LM-3S-G module, this will suspend the module where you can run wiring under it and will also help cooling the heat sink on the module board. After you have purchased your hand controller, the cost per engine is going to be around $265 to $280 depending on battery size, etc. to equip each engine.

You might like the YouTube video on the RailPro install,


A manual would be nice. I assume the momentary toggle is volume up/down but seems to do very little. I have her running using a 8.4v, 5000 Mah RC car battery for the moment. Good speed but waiting to see what battery life will be. Need to cycle it a couple times to wake it back up. Its been stuffed in another engine I havent run in a year or two. Speed is good, proper branchline and yard speed. But I want some duration and to get the volume to about half what it was. Can I just unplug that backup battery and let it stay put? I have things mounted on top of it right now. Using an RC car speed controller, which seems to work fine and the heat sinks stay cool. Yes my controller is center off on either knob. I am using the big knob for throttle/direction. So that leaves channel 2 free along with the bind button. I only have 1 grade crossing, so I am just using a magnet to trigger the horn sequence. Since its just the grade crossing sequence, and not a single blast, RC control over that really isnt necessary right now. Is it top notch sound, no, but its plenty good for garden use!

That is an early Phoenix Big Sound board, m#95, 96 or 97… You can trigger the sound functions with a magnetic reed switch, relay and or any control that offers a NO (normally open) switch.

Li-Po’s can be charged with a single power port, balance pigtail or not. Works the same as a Li-Ion with protection board. That said Li-Po’s do not typically have a protection board, experience with said batteries and a fuse at the least are required. A Li-Po’s balance pigtail can be made available easily through a door or similar opening. You can remove the dynamic brake assembly cover and access the battery and or pigtail, this is what I generally do. My Li-Po’s work in trains, planes, drones, cars or whatever.


I will Nimh or one of the Lith/Ion that Reindeer pass sells Looking at their 14.8v 6800mah batteries if the run time on my on hand battery isnt what I want. I would like to see 2 hours atleast out of it being 5000mah. The speed range was fine but I am running near full battery voltage which would shorten run time, along with consuming power for the sound board and RC control system. Engine is back recharging now, normally these Nimh batteries need a cycle or two before I see full run time from them after a few months of slumber. It wasnt totally dead but was low for the first charge and run cycle and it charge time was a bit short before it said it was done. Round 2 we shall see how she does. This is without the shell and lighting going. To big a pain in the ass to take these apart, just running bare chassis till I have things where I want it. Waiting on detail parts for the cab roof anyways including the Prime beacon light. I have a circuit that will drive 4 LEDs in the proper flash pattern. Just need 4 tiny ones to group together and stuff in the scale beacon dome when it gets here.

That said, be it early Phoenix or Soundtraxx. Can I run her without that backup battery board hooked up? With onboard battery there wont be any interuptions of the track power obviously. Thanks Mike

Mike, the backup battery is just to keep the sound on while the track power is too low. So unplug it, but leave it there if you want.

I guess it could be a Phoenix sound board - I have been confused before as they look alike. I’d look on the other side for a board name/number?

Thats is not a Sierra Board. That is a Phoenix Big Sound Model 96/97 introduced in 1995.

As for running a battery back-up, I convert my Sierras to run Supercap instead. Three 2.7 volt 6-10F in series does it with no modifications other than replace the battery with the caps. If you are “squeemish” put a 1 ohm, 5 watt resistor in series with the caps but it reduces the time on after shutdown. The three 6F caps run the sierra ~1/2 minute, depending on volume and its lighting goes even longer.

Model 97 board

I thought it might be a “big sound” board from Phoenix. A friend has the LGB/Aster K28 and the volume control is done the same way, along with using track magnets to trigger the bell and sound. The early dim headlights tells me she is an early run GP38-2, so predating the more modern sound boards we have. Still sounds great. Sounds work great without any backup battery connected, I can bring her right to a stop as the sounds will fall to idle with the throttle knob just before the center off position. Not bad for RC car speed controller and a 8.4v(7 cell) 5000mah Nimh battery. I added a red micro toggle to shut off the locomotive and a female charging socket on the bottom of the fuel tank. The shell is just sitting on the chassis as I have more mods to make. The early headlights on this just plain suck, cant even tell they are on in the daylight. So some LED’s are in order. I will do that when I do the roof details and beacon install. Once I see how much room is inside the beacon dome, I can see what micro LED’s I can find that will work with the flasher circuit I have.

Looks real good Mike! (

Nice run with the new stuff Mike!