2014_03_13 Modding the G Class lighting Boards

2014 March 13

G Class top light board for Headlights and Number lights.
The board will need to be modified to allow separation of the lights (damn Chinese don't obviously understand NMRA standards)
Ok remembering that a simple DCC sound conversion can be done by plugging a new speaker and decoder of your choice into the 8 pin plug after you remove the DC keeper board. For fellow masochists, read on...

(This is how I see the circuit? If I have it wrong please send the correction so I can fix it up for future reference.)
Pin1 to R3
R3 to LED3 +ve AND to C3
LED3 -ve to LED1 -ve
LED1 -ve to C1
C1 to LED1 +ve
LED1 +ve to R1
R1 to Pin3

Pin2 to C3,
C3 (under) to LED3 +ve (NMRA Blue)
C3 (also) to R3 to Pin1
LED3 -ve (NMRA white or Yellow) to LED1 -ve (NMRA Green or Purple)
LED1 -ve to C1
C1 to LED1 +ve
LED1 +ve to R1
R1 to Pin3

So Austrain switch positives and Common the negatives.
How can this work with a tsunami to NMRA standards which switch negatives and common positives?

Pin3 to R1
R1 to LED1 +ve
LED1 -ve to LED3 -ve to C1 to LED1 +ve
LED1 +ve to R1
R1 to Pin3

LED 3 = Headlight (Wrong LED should be white NOT sunny white)
LED 1 = Number Lights (Best number lights I have seen)

This is what I would like to do :D

De-solder all LED's and turn them 180 thus creating a NMRA Positive common!
This would solve all problems on the top board at least.

Also swap the white marker light (bright white) with the Headlight on top board (sunny white)
This will tone the markers down and fix the permanently low beam headlight.

What I will probably do due to my lousy soldering skills

Unless advice given here and elsewhere suggests another fix, I will  cut all tracks on the light boards and run three new wires from the LED's via the resistors to the Tsunami. The marker lights will get a dab of yellow paint and the Headlight stay as it is.
I wonder how many others apart from James will take control of the lighting on these things :D

Edit 1
According to the R&D guys at Sandown for Austrains, the 4 screws fixed under the middle of the bogies was not supposed to be used on the G Class. As the G Class has a one piece major body it only required fixing by the couplers as with most other Austrains Diesel previously produced. He said the 81 Class shares the same frame with new bogies as well as a two piece body. The 81 had a "bridge" chassis rail externally on both sides of the engine, and this was built as a separate piece, and so will need the body screws. I have a sneaking feeling the 81 Class delays are caused by mods and hopefully this is one of them. So remember once you get the screws out, heave them!! and hopefully anymore assembly at the factory will be without the bloody things :)

EDIT 2 Dumb Arse Electrical Question :)

I have a LED tester purchased from Jaycar. It has 7 A(+ve) and K (-ve) pairs of terminals marked in mA 1.0, 2.5, 5, 10, 10(?), 20, 50.

When I move the led up the rows LED's dim or brighten. So I guess the resistance changes. However when I put a meter on the pairs I get about 12.4 volts. (dropping to 10.4 when a LED is glowing) Without this box 12.4 volts would destroy the LED. Ok test tells me resisters do not reduce voltage but they must reduce current? I was a bit surprised by the readings, is all.
LED's are rated in low volts 2.4? When I connect the LED to  4 volts at the tsunami, the LED does not light.(1k resistor in circuit) When I put a meter on the tsunami outputs I get 2 010 with the space but no stops in 2o DC or 45100 0n 200AC scales So what should that tell me?


  1. Rod, did you see this http://www.gtsparkplugs.com/Dropping_Resistor_Calc.html

  2. Yeah thanks Dan. See it working but my tester still shows 12 volt Led Off and 10 volt LED glowing
    Ha Ha Someone once said always use a !k resistor at 1/2 a watt and you cant go wrong ;)
    "Hill Billy Electronics" HeeeHaaaaw!


All comments and suggestions from like minded individuals always welcomed. Help make this railway better :D