Digitised LGB G Scale DUO userguide

A visual user guide to operating a DCC Digitised LGB DUO Shunting loco ( a 1993 ANALOGUE model which offered remote controlled uncoupling ) Completed in January 2023 ( purchased from the Member's Sales Stand at Solent's Wickham Show in November 2022 ) giving it a ne lease of life - we look forward to its owners bringing it to use on our Shunting Puzzle at East Horsley in March 8-)
DCC Control uses F0 for Directional Lighting, F1 for the Cab light, F2 and F3 for the Front and Rear Remote controlled Uncouplers respectively, and F4 adds independent control of the rear tail lights ... allowing for no tail lights when hauling a train and a 'parked' indication of red front and rear.
The LGB UNcoupling Mechanism uses end-off-switching motors (wired common negative) to lower the loco couplnig hook, and push the adjacent wagon/coach away with a push from the lower horizontal bar ... and this works even when the adjacent wagon has a hook - NO PROBLEM.
The ORIGINAL 1993 electronics diverted a 'low' voltage from the analogue contollers 'drive' voltage to either of the uncouplers ( depending on direction/polarity ) - with the validity being identified by 1 or 2 of the coloured lights on the cab roof; higher to full voltage was then switched to the loco motor instead. DIrectional lighting was 3 white bulbs in each direction.
The MOTOR BLOCK of the period was 'unisolated' and therefore the first part worked on: LGB made 2-wire and then 3-wire connected Motor Blocks in their early days ( 2 wire with maybe a basic bulb light, then a 3-wire connection to 3 brass strips was later used for diode-controlled directional lighting.
'Digital Compatible' Motor blocks come with 4-wire connections: separated Track and Motor connections.
Conversion from 2 or 3-wire is actually quite easy - BUT often requires the complete disassembly of the chassis block which were a left and right half at the time - unlike the tops and bottom access of modern 4-wire motor blocks.
CUTTING the LINKs between motor and track is straightforward - and the extra / separated track pickups are best rebuilt with flat strips such as the Phosphor Bronze Pickup Strips which are commonly available: these can ensure good electrical contact to the Plungers and Pickup Skids, and still pass through available gaps - 1 or 2 extra routes out now being required from the track to the DCC DECODER.
In this oproject I used a Massoth L decoder: Similar outline to the standard LGB silent loco decoder, BUT with extra (soldered terminal) function outputs.. The decoder rating is 1.8A max, but only 30mA on the extra functions .... and by default will be at just below track voltage ( I assumed 18V in calculations as I use Roco Z21 / Multimaus systems using an 18V SMPS supply or 20-22V for Z21 XL / Massoth Dimax Systems )
A DCC decoder and its functions are usually common positive.
The LGB Coupling motors/pcb, the DC_DC Inverter, and the 12V Flashing LEDs I used are all Common Negative - isolated by using RELAYS to switch the Coupling Motors, with the DCDC Inverter preadjusted to 12V for the LEDs and cupling motors ( they operate reliably at 9V, and were designed to operate on a detected 'low voltage' output of an analogue controller - with higher voltages going to the '24V' dc loco motor.
'Pre-wired' LEDs were used for convenience when replacing the original bulbs - this both reduces the quiescent current load on the decoder/controller and avoids the increased bulb replacement arising when used on contstant full voltage - an extra series resistors added to the decoder +ve supply to avoid the need to program down the voltage.
These locos are still offered on the 2nd hand market - but often at inflated prices !