DCC and Bachmann Spec F7 A/B

[skipgear]

Does anybody have any links or suggestions to installing DCC decoders in the Bachmann F7 A/B sets?

It looks a decoder will just fit between the top of the frame and the shell but I think I am going to have to do a little milling to get some extra space. I also need to modify the frames to issolate the motor.

 

[tommann]

Hi;

I have a A & B set to do too. Any info would be great!

Thanks,
Tom.

 

[ross31r]

AFAIK, you cant do it without getting the Aztec Models frame for the units - i posted this question up a few months ago.

Hence i have abandoned my F7 ABA set and switched to Kato and Intermountain Fs and FTs for my N Gauge

 

[skipgear]

There is no need for the Aztec frames, the modifications are not hard to do at all. It takes about 10 minutes with a dremel tool to get them ready.

I have completed the B Unit and will try to take pictures when I do the A for a quick tutorial. The conversion can be done completely with a dremel tool, sanding drum and 1/16 drill bit. I used a belt sander to make things go a little faster removing material from the frame. I still need to decide how I am going to tackle the headlight on the A unit but I don't think that will be very difficult. The fix I have in mind might actually help stop the light leakage into the cab of the loco.

Attached are two images of the decoder installed in the B unit.

 

[tommann]

Skipgear;

What decoder did you use?

Thanks,
Tom.

 

[skipgear]

The decoder is an MRC decoder.

 

[ross31r]

Frame looks different to that in my F7s - and personally i wouldnt use an MRC decoder - i used to use them but they went wrong so often i dont anymore!

 

[skipgear]

The loco's are from the most recent batch from Bachmann. I have an older standard Bachmann F7 (at least 5 years old) that has the same style frame. As far as I can tell, the difference between the two is much better printing/paintjob and the 5 pole motor vs. the 3 pole in the standard.

As far as the decoder, I am doing these for a friend and that is what he handed me. I have done a half dozzen different loco's for him with these decoders and all are working fine, although we did have one that was DOA.

 

[skipgear]

F7 DCC Install Step by Step (Step1)

Step 1 - Disassemble the loco.

Everything is pretty straight forward. Before removing the motor from the frame, mark the top side of the motor with an orange marker if you have it. The orange DCC wire will eventually connect to this terminal. Make sure to remove the small contact spring from the left frame. Note the front truck and rear truck of the unit so they can be reinstalled in the same location. This is important if you have already broken in the motor, the gears have worn to a match and you don't want to change them around and have to go through break in again. Straighten the leads on the headlight for later. If you haven't installed MT couplers yet, do it now while things are apart, it is much easier.

 

[skipgear]

Step 2 - Mark the frame for modification.

Mark the frame as shown. The area removed from the upper rear can be adjusted to suit the size of your decoder. Make sure to mark the small tab from the right side frame for removal. It acts as a motor contact so enough must be removed so it will no longer make contact.

 

[skipgear]

Step 3 - Modify the frames.

Remove the material in the marked areas using your favorite tool for the job. I screwed the frames back together and used a bench top belt/disc sander for roughing out the large area then a Dremel and files to clean it up and make the final fit. Take the frames back apart and use a Dremel or file to remove the tab. After you have removed the needed areas, clean the frames with soap and water to remove any shavings and filings. Then check to make sure the motor terminals no longer make contact with the frame.

 

[skipgear]

Step 4 - Adding main power connections.

Since you cannot solder to the pot metal frames, you must create a screw contact to attach the main power leads of the DCC decoder. Size is really up to what you have available to you. I used 2-56 button heads because I have plenty from my RC racing equipment. Drill a hole appropriate to the screw and tap you will be using in the place shown. There is a cavity in the casting directly below the hole placement so you don't have to drill very far to break through to the inside of the frame. After drilling, tap the holes and make sure that the screws are not too long and protrude into the flywheel pocket. If they are too long, shorten them so that they won't hit the flywheel. Mark the right frame with Red and the left frame with Black (shown in the next step).

 

[skipgear]

Step 5 - Installing the DCC decoder.

Now you need to attach the decoder to the motor. The orange wire will connect to the top terminal and the gray wire will connect to the bottom terminal of the motor. Remember marking the top of the motor with an orange marker in the beginning. If you didn't mark the motor, another easy way to tell is the plastic insulating shield has a hole punched in the bottom flap. Cut the DCC leads down to the minimum length you feel comfortable with. For the MRC decoder shown, the Gray wire was 1.5" and the Orange was 1.25" long. Solder the wires as shown, making sure to use the least amount of heat and solder so as not to melt the plastic of the motor. Also make sure you don't leave any solder blobs on the connection, if the joint is too thick, there is a chance it could contact the side of the frame when you reassemble things.

 

[skipgear]

Step 6 - Reassemble the frames.

Reinstall the motor in the right frame. Then install the trucks. Now is a good time to make sure the contact wipers on the trucks are bent properly and clean. Also note the plastic insulating washers between the side frames, they are cut different for the front and rear. Don't forget the plastic insert for the fuel tank mounting screw. Carefully replace the left frame making sure to line everything up and not catch the pickup wipers on the inside of the frame. Screw the frames together, checking for binding as you go.

 

[skipgear]

Step 7 - Headlight and Main power connections.

First cut the red and black wires to length and install them on the appropriately marked post. Next cut the wires on the headlight shorter, aprox. .25" final length. Cut the wires on the DCC (Blue & White) to the right length, slide a .25-.5" piece of small heat shrink tube on each of the blue and white wires, then solder them to the headlight. It doesn't matter which wire goes to which lead of the bulb. Slide the heatshrink over the connection to insulate them and then replace the bulb in it's original place. I used some double sided scotch tape to mount the decoder to the top of the frame. It also added an extra layer of isolation from the frames. It is a good idea to tape down the wires to make it easier to replace the shell and keep them out of the gears.

 

[skipgear]

Step 8 - You're Done

Place it on the test track make sure it works. Program the decoder.

Step 9 - Replace the shell and have fun.

 

[ross31r]

lol, you dont fancy doing my F7s do you?

 

[skipgear]

Ross, I wouldn't mind doing them but by the time you add in the cost of shipping them from the UK, and then return shipping, would it be worth it?

 

[ross31r]

lol, probably not but they didnt cost me full price to begin with!