If you have an LGB F7A and/or B unit this might be of some value to you. I bought an F7A and B unit in SP and NH within about a year or two after they came out. When I put them on my track and cranked up the transformer, I was disappointed to find that they seemed to require a huge amount power to move at speed, and never did get to what I would think of as Passenger train speed. As I result I almost never used them. The sound from the B unit was great, but it would not work without the A unit, so I couldn’t use them with my Aristo and USA Trains diesels.
Recently I have been converting my entire collection of engines (over a hundred, talk about getting carried away) to Battery/RC operation and I came to my LGB F7s. I had some problems figuring out the wiring. The A unit, had a circuit board in the middle of it that had this donut shaped gizmo with copper wire wound around it. It just looked like it would take the power of a nuclear power plant to operate it! So I called it the Donut of Death Board (if you’ve seen the movie, Spaced Invaders, you will enjoy the humor here all the more). As I couldn’t figure the wiring out I just resorted to my old stand-by of completely by-passing the board and direct wiring my leads, that would eventually go to the battery/RC car, to the motors in the trucks. Figured I would lose the lights and sound, but I was/am determined to completely abandon track power no matter what the cost.
Then I went to run the unit. To my surprise, it ran great. I could get passenger train speeds with no problem. So what the hell is the Donut of Death doing?! Was the sound unit in the B unit sucking down a bajillion watts? Who knows! You track power people could do the same sort of by-pass, wiring the track pickup wires directly to the motor supply wires and get the same result.
Then I turned my attentions to the B unit with the wonderful sound unit. LGB manual says you must have an A unit to drive this puppy. Is that really true. Was the Donut of Death in the A unit doing certain mysterious electrical magic that only the B unit could digest? I found that it was not. I wired my battery lead into the sound unit using the two pin connectors provided by LGB. I was thus avoiding those dreaded ribbon cables in the interior of the unit, which scare me greatly. I cut this provided 2 pin connector wire in halve and wired the cut part to my battery wires. The sound unit worked great and did not seem to take much power. I can now use these wonderful sound B units with any engine I want. There is chuff-like wiring that goes into one of the two trucks that makes the sound unit dance. If you are a track power person, you could use the other truck to pick up power and direct it to the 2 pin connector without messing with any ribbon cables, and you too can use these wonderful sound units, trailing behind any engine, although I do suggest you only use diesel engines. If you use it behind a steam engine, people will think you are some sort of pervert.
I then tested the use of the 4 pin cable for sound between the A and B units, and the A unit’s speaker fired in an excellent manner along with the B units speaker. Thus I had stereo sound! All this without the Donut of Death being involved in the wiring!
I have not got the lights in the A unit working yet as there is a 10 pin ribbon cable involved, which I am afraid of. But I am sure it can be done, also, without the Donut of Death. I do not know what the Donut of Death is doing. Perhaps some of you out there can enlighten me about the error of my electrical ways. But now I have two great running A units and two sound B units that make all of my diesel audio operations a joy. Track or Battery power, matters not, you can do the same.
OTOH it’s from the makers of “we adjust it for our own pleasing proportions” (“G - wie Gummi”) items.