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ORD-3-rc Universal Spaxbooster / DDXBooster / DCC232 Booster 3Amp stabilized, with Railcom cutout

The real thing

ord-3-rc_pict03.jpg ord-3-rc_pict01.jpg

The Spaxbooster is a well known booster, very easy to use , with a nice stabilised power output.
Without a regulated power supply in the booster, the output voltage to the trains will fluctuate with the amount of running trains.
Also different transformers give different voltages.
Therefore , the original Spaxbooster is already equipped with a regulated power supply for 15 Volt.
But that voltage cannot be changed, meaning that Spaxbooster is made for HO-scale.
Also the type of power supply is generating much heat, specially when used transformer is giving more voltage output as expected.
The ORD-3 does have a far more efficient switching power supply, and the output can be adapted to the different voltages, dependable on the used scale.
Voltages of different scales according to the NMRA DCC standard are:

Large scale 18V
0/S/H0/TT scale 15V
N scale 12V

The selection of output of the ORD-3-rc is done by dip-switch.
ORD-3-rc connects to a Central unit by means of standard LocoNet connector, using only two wires.
ORD-3_rc is also useable for a direct connection to Serial port, USB<>RS232 cable. or even Raspberry Pi, where the connected computer is set to run DCC232 in Rocrail.
Furthermore, ORD-3-rc is adaptable for direct USB connection and it has the standard cutout for use with railcom decoders.

Three standard LocoNet connectors are available in front.
The signal input of ORD-3_rc is galvanic isolated by means of ultra fast opto-couplers.


ORD-3-rc has a few nice features:

  • Most connections and signal-leds are on one side of the unit, making it easier to fix it to a front panel.
  • On board supply is stabilised for the chosen voltage output.
  • On-board dip switch to select N-HO-G output.
  • Wide power input range : 16-20V ac / 19-30V dc, due to the use of switching power supply.
  • Power output shut-off 30 mSecs after no pulses received (according NMRA spefications). Your precious N-Lok will not run away on power off.
  • Perfect suitable as DCC232 booster. Optionable also for USB.
  • Automatic stop at short circuit and automatic try to restart
  • Fully compatible with CAN-GC3 command station.
  • Can be driven with any DCC and/or Motorola command station
  • Multiple ORD-3-rc units can be used on your layout, driven by the same central station.
  • Railcom cutout activated.
  • Lenz compatible DCE input.

Warning !: Due to railcom cutout option, this unit cannot be used together with standard ORD-3 units.

Mounting instructions

First start with all small resistors and IC sockets.
Then small capacitors and small elco's.
Then all connectors, leds, fuse and dip-switch(or 3 pin header).
Before mounting VR1,VR2,U1 and GR1, first fix the cooling block with two screws.
After that place VR1,VR2,U1 and GR1 in the pcboard and fix them with the clips.
Be sure that all parts are flat to the surface.
After that, cut the wires at the bottom at 1 mm outside the pcboard surface, and solder the wires.
Then fix resistors R5 and R14, and be sure to use the little standoff supports. Resitors will be very warm when in function.
In parts package (available from, these supports are included.
At last fix C9,C11.
Before inserting U2, test power 5V on pins 1 and 8.

Important notes

  • ORD-3-rc, connected via serial Port for Direct drive is only supported for DCC232.
  • ORD-3-rc is NOT suitable for Motorola commands, use ORD-3-V2 if you need that.
  • ORD-3_V2 can be used for DCC232 OR LocoNet, but not at the same time!!!!!

As with all published units from GCA, the transformer used to supply this booster MUST be dedicated only to this unit.
Any connections from this transfomer to anything else (except of course the 230V supply) is strongly discouraged.
It might result in very strange and sometimes dangerous situations.
Keep it separated !!

LED configuration

LED Colour Indicates (if on)
LED1 green Power on
LED2 red Flashing » booster off
Lit » booster ON.

Hardware files ORD-3-rc

The schematic
The pcb and parts positions
The bill of materials
N.B. Only complete kits from GCA are supported!


The PIC12F629 in this unit provides control over the output.

This zip file contains both firmware with and without Railcom.
It is important to use without Railcom when more then one boosters are used in the same layout. (Like for Spax system)

ORD-3rc with USB-Serial converters.

Serial ports are getting exotic in personal computers allthough in the professional machine world they are widely available.
But there are very cheap boards available to be used in your PC, adding two or more standard COM-ports to your PC.
We have to wish you good luck with Windows 10 installation!.
But for laptops, all this is no option.
One possibility, not the cheapest one, is the use of a SUB D9 USB-F connector.
It fits straight in the ORD-3-rc board, and the driver is loaded usually automatic when connected to the PC.
The other option is using a USB-RS232 cable.
There is no guarantee that the cable you already have is working, but it is worth trying.
Basicly the ORD-3-rc input is set for a general minimum of 10 Vpp from a standard serial port.

ORD-3rc with RocNet.

From 5tj July 2019 it is possible to use ORD-3rc with DCC232 protocol , connected to S1 on GCA_PI01.
Further info :

Multiple ORD-3-rc connection

In both LocoNet or DCC232 situation a second ORD-3-rc can be connected with standard RJ12 cable to the first.
And the third to the second, etc. The three RJ12 connectors on front of ORD-3 are all the same and interconnected.

But ALL ORD-3-rc units with separate Transfomers!!!!!!!!!!!!!!!!!!

Alternative cooling

If you do not like to spend money on cooling, it is possible to make it yourself.
Simply look at ORD-2 how this done.
It is not necessary to isolate both chips from the metal, but consider that the alu plate will be connected to 0V of the board.

Dip-switch Settings

The settings a in this table are also printed on the PCB itself.

dip 1 dsip 2 scale


The tranformer or power supply (=ac/dc adapter) for this unit should minimal 50VA.
The table below shows the best voltage regarding to the used scale.

Voltage ac out power supply dc out scale
12-20V 15-30V N
15-20V 18-30V HO
18-20V 21-30V G

Note :
Transformers do NOT have dc out! Except the speed/control output from any train transformer for two rail systems.
Using DC supply is no problem, polarity is not important.

ord-3-rc-en.txt · Last modified: 2019/07/04 13:26 by phg