LGB Forney

DCC CONVERSION of LGB Forney #21

Using a Digitrax DG580L
and a PH Sound system
By Ross Webster

I first tested the decoder as per Digitrax's instructions and followed all of their installation procedures.

NOTE: THIS CONVERSION MAY VOID ANY, OR ALL OF THE LGB WARRANTY
(Since this was an old three wire unit it probably did not matter.)

Current measurements, lights and smoke at 5 Volts

Motor Free .7 amps

Motor Lock 2.9 amps

lamps 27 ma each

Smoke 200 ma

Cab lights Wire Identification Connections

black common

Red cab

white back-up

Disassembly

Remove handrails. The mounts just pull out of the boiler and when the two are out you will need to tip the handrails up to pull them out of the cab as they have a 90 degree bend in them. Same for both sides.
Remove the three boiler pipes. They just pull out.
Remove the two brass rods to the cowcatcher. They just pull out of the boiler first.
Remove the ash pan on the bottom by taking out one screw in the center.
Remove four screws in the bottom of the tender on the bottom. (where the coal goes as I guess it is not really a tender) Lift back of cab a bit as the tender portion hooks under it. If you are nervous about flexing the bottom that much you may also want to remove the two screws in step 9 as they will need to come out anyway.
Remove two small screws in side of boiler by smoke box.
Pull smoke box out watching not to catch any wires. You may need to turn it sideways as it gets by the front of the unit. THERE IS A SMALL BLACK PIECE THAT SPACES THE BOILER UP FROM THE WEIGHT IN THE TOP CENTER. It may fall out on you so just watch for it.
If it did not fall out remove it now.
Remove two screw in side of boiler just about the bell area.
Remove two screws from bottom in front a corner of cab if you did not already remove them in step 5.
Slide boiler forward and tip it up over the engineer as you come by him. It will come. Watch not to break any wires.
Remove two small screws that hold rear of boiler cover on and remove it

I then removed the existing boards as they would not be used again. I originally added resisters to the lights and the smoke unit as they were 5 volts. I later changed the bulbs and smoke unit to 24 volts units for simplicity.

Power Block Isolation

The first job was to separate the rail from the motor in the power block. Since the board was removed the wires that connect to the block should have already been removed.

Remove the four screws holding the weight on.

Check which side of the motor is positive by applying some voltage to the motor lead and the rail which is still attached. If you attached the positive to the left rail and the negative to the motor pin far right the unit will move forward. This verifies which is the positive lead.

Remove the screw, washer and beveled washer and the rod that goes to the piston from the rear wheel. Be sure to remember how it goes back together. Beveled washer first with hollow to inside, then the rod, flat washer and screw.

Remove the two screws in the bottom of the boxes to allow the motor section to move out of the block.

Remove the two screws in the top and it will lift off. The ends will also fall off.

Soldier an orange wire to the positive motor lead. You can now either soldier a gray wire to the negative side, or use the existing pin, and put the motor back in. Make sure you have not changed the quarter of the wheels. You will need to move the pick-up leads a bit to get it in. Carefully test the motor by applying some voltage to the motor. Positive to the orange. And negative to the gray and it should move forward. If it moves backward they are reversed. On my unit the positive was the one that was attached to the left rail. I used all wires soldiered as I have had previous problems with the pins loosening off.

This was one of the earlier units and it only had three pins instead of four. When I did the WP&Y Diesels I had added a fourth brass rod. I later found that it was just as easy to soldier a wire directly to the motor lead and increase the hole size to allow it to come through. Having completed that I reassembled the motor block and reinstalled it.

(note there has been a colour shift in the picture of the wires. Please follow the decoder procedure except the left rail is red in G scale)

Decoder Location

I wanted to bolt the decoder to the weight but there was not quite enough room. I notched out the weight to allow it to go in and mounted it to one side with a metal screw as per the photo.

Sound System PH

The sound board went into the top of the tender with velcro once all the wires were connected. The PH board was wired as per the instructions. I made up a small board with two Optoisolators on it to isolate the sound board from the decoder. This also went into the tender. I also added a small 8 volt regulator to replace the batteries which went into the tender. The photo below shows the installation in the tender.

The photo below shows a small board I built to control the bell and whistle as you cannot connect directly to the PH board. This unit used some 5 volt reed relays I happened to have. I could have also used Optoisolators to do this. This board also has the two pin headlight and the three pin cab and rear light male plugs on it. Since it is close to the decoder it is easy to wire and mounts on the very rear of the weight with double sided tape. The schematic for the board is below it.

Optoisolators Mounted to small board

Optoisolators Mounted to small board, Bottom

Circuit Diagram for the Complete wiring system

The photograph below is the completed installation with the rear of the boiler installed The relay board above tucks nicely into it. Note the connectors used for the main decoder wires.
The smoke unit is the second joiner. I use the brown and the large blue and add the diode across the joiner as required in the instructions item #2.

Assembly is the reverse of the disassembly.

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