32 Class DJH model Conversion to DCC

This is a DJH 32 class model I built many years ago. The white metal kit was assembled completely by soldering in the 1980s and was a good runner on DC. It saw service during the ’80s on the old Warrimoo layout in the Blue Mountains.

I converted it to DCC in 2015 using a Soundtraxx Micro Tsunami model TSU-750 #826001 Light Steam. This is a generic US decoder which serves the purpose but lacks a true NSWGR whistle. I can live with some compromises! The USA Reading 6 Chime whistle was my compromise.

These days my preferred decoders are ESU Loksound and there are some local suppliers who can supply one with the correct 32 class sound file.

The first step was to dismantle the loco for access to the boiler and chassis for installation of the speaker and headlight and to replace the motor and flywheel as well as adding additional power pick-ups as below:

The motor I used was a NWSL Flatcan 12 x 20mm Double 1mm Shaft (#1220D-9)
I ordered mine on-line from this company. You may be able to buy one, or similar alternative locally. I added:

    • a flywheel – 1.0mm shaft ID, 10mm OD not countersunk #435-6
    • shaft adapter bushing 1.0mm ID x 2mm OD to provide enough diameter to match the gearbox shaft #10171-9
    • nylon (nitrile?) model aircraft fuel line to flexible couple to the gearbox.

The headlight was a pre-soldered  Warm White 0603 SMD LED purchased on ebay. These have leads which are long enough to go through to the tender. But they are fragile and require handling with care. An 0603 LED is 1.6 mm x 0.8 mm x 0.6 mm thick and seems a good size for a steam loco.

The photo below shows the 32 class headlight – I drilled a tiny hole through the base of the headlight, right through the rear mounting and into the firebox. It needs to be just big enough to take the two wires. The LED was held in place with a speck of canopy glue. The alignment of the drilled hole is shown in red. The wires were held in place within the boiler barrel with small dabs of blu-tack.

It is vital that a series resistor be placed in either feed wire to the LED. I have adopted as standard, a 3k3 (3,300 Ohms) resistor as there is no need for NSWGR lights to be too bright. Remember that a resistor has no polarity ie. can be installed either way around.

The Speaker – I have separate posts to describe fitting a speaker to the smokebox but to save you searching, here is the gist of the 32 class receiving a speaker in the smokebox. Facing upwards towards the funnel which needs to be drilled out. This is the sugar cube speaker enclosure under construction:

The cylinder is cut from a small piece of plastic tube to match boiler ID.
End caps have now been added. The wires should be brown but I ran out!

While the boiler is off the chassis, extra pick ups can be added.

The wipers are phosphor bronze with the front ones the correct size (0.008″) and the rear ones, looking like crow  bars at 0.015″ (they haven’t impeded the loco!). The wipers are only needed on the side with insulated tyres.

To get the wipers out to the correct spacing, a plastic insulating piece was combined with a small piece of PCB (printed circuit board) to make a mounting to solder the wipers and the connecting wire to the tender.

The Tender

Access needed to be provided to the tender space as shown below

A plastic ferrule was glued to a hole drilled just forward of the front bogie pivot – so that the wiring can safely pass into the tender. The other half of the exercise is getting the wiring out of the locomotive

Here we see 8 wires emerging:

  • Orange and Grey – to the motor
  • one pair of Red and Black – to the Right & Left track respectively.
  • one pair (incorrectly) Red & Black which should be both Brown for the speaker
  • one pair of thin and clear LED headlight wires. These are identified by one wire being shorter – this is the Cathode and connects to the White decoder wire. The other wire is a little longer and is the Anode wire which connects to the Blue decoder wire. They need to be marked before the LED is installed and I coloured the end of the Anode wire BLUE with a marker pen.

The tender is where the fiddly wiring occurs. Since there are 8 wires needing to be connected to the decoder, a plug and socket arrangement is difficult. I choose to make those connections via a small pair of home made PCBs. They are shown below

The photos below show handmade simple PCBs made with a small saw and a mitre box. The single sided PCB material can be bought on eBay from sites such as this one. The little PCBs are cleaned thoroughly on the copper side with very fine wet & dry and can then be tinned with a little resin cored solder. Make sure the tracks remain electrically separate.

I made 2 for the tender above so that I could solder the 8 wires from the loco to the 8 wires from the decoder:

Here you can see the 8 connections from the decoder. The resistor (1k – should be 3.3k) is settled behind the LH PCB with one end of the resistor joined directly to the white wire from the decoder and the other end of the resistor soldered to the rear PCB strip. That will be where the Cathode of the headlight lead is soldered.
The other headlight lead (marked with blue felt pen) will be soldered to the strip connected to the blue decoder wire.

Also visible in the above photo is another little PCB pad which will carry the phosphor bronze wipers to the tender bogies on the insulated wheel side.

The photo above is actually a 36 Class tender bogie but you can see how the principle is the same. Similarly, the photo below is of the front of the 36 class tender showing how the little PCBs were fitted to this slightly roomier space.