Photo 1
The ingredients! One Bachman 37, a bass-reflex speaker, an ESU soundchip and a spare bogie (optional! don't ask!).
Photo 2
Firstly remove the six retaining screws, under the red marks , be careful with the ones under the buffers though as they can break off the buffer shanks on the way out. I've done it!
Photo 3
Unsolder the red and black wires from the pick-ups marked R & L on the PCB (or unplug them on the latest 21 pin versions)and the three wires to the lights, marked in red at each end, but make a note of where they go first. Or just unplug the two pin connector on the really early ones! You can then remove the bogie retaining screw and gently pull the bogie and carden shaft forward and down to release them, trying not to damage the wires though as they pull through the chassis.
Photo 4
Remove the four short retaining screws, marked in red, to remove the plastic chassis. While the bogie's are out of the chassis, now is a good time to check, adjust, and paint the pickups to make them work and look better.
If your model is the latest version with these switches-
Photo 4a
The blue, orange and yellow wires on the PCB marked 1 to 6 will also need unplugging-
Photo 4b
The red and black wires seen in the photo are the disconnected speaker wires.
Photo 5
or
Photo 5a
Remove the retaining screws that hold the metal weight in and discard all, the weights do come in handy on my work bench though, so I save them.
Photo 6
You can either snip off the plastic columns now or drill them out at a later stage.
Photo 7
Using a razor saw remove just enough of the protruding plastic at the insides of the tanks to allow the speaker in.
Photo 8
Photo 9
Drill as much of of the the central rib out as possible before snipping and cutting out the remainder. This allows the speaker to sit as low as possible.
Photo 10
Once the inside of the tanks are cleaned up you need to decide which way round the speaker is going to go in. You'll need a lot of holes in one tank with just two groups of four in the other.
Photo 11
You may get the holes straighter than me! Its a longer job than just chopping the base of the tanks out, but it does help to protect the delicate speaker.
Photo 12
The speaker should now squeeze in nicely with the wires sticking out to the side. I also put a sticky pad on the back of the speaker, without removing the second backing paper. This stops any movement of the speaker which can cause distortion.
Photo 13
The plastic chassis moulding can now be reattached to the motor block, taking care not to trap the speaker wires. At this point I glued a small piece of copperclad sleeper strip with an insulating slot cut into the copper onto the side of the motor. This allows the brown wires from the chip to be soldered or unsoldered from the speaker wires in the future if needed without the need to remove the speaker. The alternative to this is too drill through the chassis block and connect the speaker wires to the SP + and SP- points on the 21 pin chassis PCP.
Photo 14
At this point the speaker wires were cut back and soldered to the copperclad and the chassis reassembled. The red and black pick-up wires can now be reconnected and the chassis given a good run on DC power, just to make sure it all bedded back in nicely with no short circuits. If yours is the latest chassis type that had the switches disconnected you will find that the tail lights and cab lights no longer work. If you wish to reconnect them connect contacts 1&2 together for the tail lights at the no 2 end. 3&4 together for the tail lights at the no 1 end, and 5&6 together for the cab lights.
Photo 15
Next I fitted a 25mm square piece of thin black plastic-card over the wires at the end furthest from the 8-pin socket. This tidies the wires out of the way and makes doubly sure the chip cannot touch any part of the metal chassis block. Another sticky pad is used to hold the chip in place.
Photo 16
The chip fitted to the sticky pad with the 23mm standard speaker still attached. If its a 21 pin chip the speaker will be a 40mm x 20mm rectangular one. Make sure the chip is clear of the contacts for the cab lights.
Photo 17
The wires are unsoldered from the standard speaker and attached to the copperclad strip. As you can see I use blue-tack to tidy up the wires and make sure they don't get where they shouldn't be. I also cut any exposed core from the violet wire and cover the end with insulating tape.
Now the chassis is ready for its DCC test run (thrash!)
, after checking it first on the programming track of course! Hope this is of some help, quite a few said they'd used it when it was published! Kev.
Top
