# Help powering LGB F7b



## BodsRailRoad (Jul 26, 2008)

Hi, 
I decided to power up the LGB F7b dummy engine. I have already acquired 2 F7a powered trucks and am looking for some advice on which decoder to use.

The F7a has a Phoenix Sound card and a dcc decoder installed. 

If possible I'd like to get DCC+Sound that will match the sound of the Phoenix card, baring that a good s DCC only card.

I know that I'll have to remove the existing electronics, but other than connecting the motor blocks to the dcc card is there anything else to be aware of?

Thanks, Ron


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## piercedandan (9 mo ago)

Assuming you keep the original B unit LGB sound unit, the non-Marklin F7B units had one truck with an axle sensor for the LGB sound unit in the B unit. Unfortunately this motor block comes with axles that are smooth (can not add an axle gear). I added one powered motor block to my B unit, added weight plus I had to add a diode bridge to lower track power (I kept mine at DC only/no decoder). You could just use one driven axle gear and keep the original speed sensor. Since mine is ABA, 5 motors are enough for my layout.


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## BodsRailRoad (Jul 26, 2008)

piercedandan said:


> Assuming you keep the original B unit LGB sound unit, the non-Marklin F7B units had one truck with an axle sensor for the LGB sound unit in the B unit. Unfortunately this motor block comes with axles that are smooth (can not add an axle gear). I added one powered motor block to my B unit, added weight plus I had to add a diode bridge to lower track power (I kept mine at DC only/no decoder). You could just use one driven axle gear and keep the original speed sensor. Since mine is ABA, 5 motors are enough for my layout.


Can't I just use 2 new F7a powered trucks and wire them directly to a dcc decoder and be good to go?, keeping in mind I plan to remove all the lgb electronics from the b unit.


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## piercedandan (9 mo ago)

Yes Ron, that is the way to do that plus add weight. You can sell the LGB electronics as Marklin does not make the original LGB parts. A great speaker is the Visiton FRS7. Also keep the 2 pin cable in place between the A and B for better track power distribution. My ABA has the 2 pin cable between all engines.


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## BodsRailRoad (Jul 26, 2008)

Great thanks, any recommendations for a good dcc only card, or a dcc +sound that will sound similar to the phoenix card in the a unit?


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## BodsRailRoad (Jul 26, 2008)

piercedandan said:


> Yes Ron, that is the way to do that plus add weight. You can sell the LGB electronics as Marklin does not make the original LGB parts. A great speaker is the Visiton FRS7. Also keep the 2 pin cable in place between the A and B for better track power distribution. My ABA has the 2 pin cable between all engines.


Hey Dan the motor blocks showed up today and they have a 3 wire plug from motor instead of the 4 leads I was expecting, I assume that the plug would plug into the stock LGB board.

How would I go about wiring this motor block into a DCC decoder, conversely does massoth make a dcc board that they would plug directly into?

Here's a pic,


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## piercedandan (9 mo ago)

3 wire motor blocks have one motor lead tied to track power. This must be undone as you need 2 track wires to a decoder input and 2 isolated motor wires to decoder out or you will burn up the decoder motor output electronics.

However, the motor blocks displayed in the picture have 4 connectors which are motor and track power, the 3 wire (Black-brown-black) are for either chuff or bell/whistle sensors. If bell/whistle then brown is common to both reeds.

Inner pair is track power, outer pair is motor wires on the 4 pin connector.


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## BodsRailRoad (Jul 26, 2008)

Awesome thanks for your help 👍👍


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## LGB333$$$$ (Oct 11, 2017)

BodsRailRoad said:


> Awesome thanks for your help 👍👍


The LGB F7 motor blocks are 4-pin, not 3-pin, as your photo shows. The 3-pin plug connector shown is for the reed switch which you don't need and can remove.

You'll definitely want to remove the old analog sound board from your F7B and, as Dan indicated, you can sell it on eBay since there are lots of DC analog hobbyists still using the old factory-installed electronics that will eventually fail. And you don't need to install a DCC sound decoder, just cable connect the Phoenix sound decoder's speaker output also to the F7B unit. You'll have to modify the F7A's rear cable circuit board for the 2-pin connector and the front of the F7B's cable circuit board for the speaker's connection. You can unscrew them and I use a Dremel cutter to break the circuit boards from the 4-pin connector so only the 2-pin circuit is used and I solder the speakers wires to them.......maintain the speaker wires polarity from the Phoenix decoder to the speaker in both diesels. And I concur with Dan, the Visaton FRS7 is a great speaker but you must Dremel down the existing speaker screw mounts......I use epoxy putty to mount a Visaton FRS8 in the F7A diesel and an FRS7 in the F7B diesel. I use the ESU 5XL DCC sound decoders in my installs for customers which has an outstanding F7 diesel sound file......go to my Website's Homepage, scroll down to the Demo Vides at the bottom, and watch the video of the F7ABA Southern Pacific install I did two years ago......it will blow your socks off! My Website: LGB Trains | Old Dominion Railways | Repairs & DCC Installs | United States 

You should also try to use the same DCC locomotive decoder that you have installed in your F7A diesel also in the F7B diesel......easier to sync the motor speeds between the two diesels. If you can't, when I motorize an LGB F7B diesel I use a Massoth XL DCC locomotive decoder and adjust CVs 2 through 6 to sync the motors with those in the F7A diesel.


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## BodsRailRoad (Jul 26, 2008)

Thanks for the input but I finished this project awhile ago, came out pretty good 😁








LGB F7B power and sound conversion.


I modified non powered LGB F7B unit with 2 LGB 65057 F7a motor blocks, using 2 Massoth 8312021 Motor Block cables attached to the 4 pins on top of the motor blocks, its controlled by a Digitrax DG583S DCC controller. I also added some extra weights. I found that I had to wire the trailing motor...




www.mylargescale.com


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