QSI into Bachmann 3-truck Shay

[ntpntpntp]

I'm never quite sure whether combined DCC and Sound installs should go in the DCC forum or in Sounds, but as I've posted other DCC installs here and they're included in the "compilation" list, here goes.....

Thought I'd spend today installing a QSI DCC & sound card plus a speaker in my Bachmann 3-truck Shay.
The decoder came from GSC member Ash (Graham). It's the Magnum version with the extra adapter board for screw terminals.

The speaker is a 3 inch 8 ohm 8 watt, one of a pair bought for £5 on eBay.

 

[ntpntpntp]

Anyway, first job was to fit the speaker in the 3rd truck "tender".
To remove the body shell, remove two screws underneath at the rear...

.. then tilt the shell up and toward the front to release from its clips

Inside, the wiring for the motor block passes down through the middle of the speaker grille.
Four retaining clips are provided to mount your speaker. Feed wiring for the speaker is already provided on the 8-way connector from the loco.

Before fitting the speaker I used a little hot-glue to secure the wiring nice and flat on the floor, away from the speaker cone.

 

[ntpntpntp]

Naturally the mounting holes on my speaker didn't match the screw locations! I ground off the speaker's mounting holes and used the Bachmann mounting clips.

Total height about 5cm, well within the 6cm clearance inside the "tender" body shell.

Refit the body shell and all done.

 

[ntpntpntp]

The loco main board is housed within the coal/oil bunker at the rear of the loco. To remove the bunker shell, remove two screws underneath at the rear...

.. then tilt the shell up and toward the front to release from its clips

(if you look carefully at the above photo, you can see the existing Massoth eMotion decoder I'd previously fitted to this loco, it's hiding under the main board!)

 

[ntpntpntp]

Here's the main board wiring as it comes supplied for analogue. (Yes, I wired it all back for DC after removing the Massoth decoder, just to make sure!)

In order to convert to DCC, the wheel pickup and motor wiring needs to be disconnected from the main board. Fortunately Bachman link all the wiring for the 3 motor blocks into the main board and provide a single set of four wires (red, black, orange, grey) that need to be removed from their screw terminals. They're a bit short though!
Wiring for the front and rear lights, cab light and the speaker is routed through a single 6-way plug that also needs to be disconnected and routed to the decoder.

With the previous Massoth decoder I'd decided that, in order to avoid any irreversable changes to the existing wiring, I would make a small connector from a small piece of strip board and some pcb header pins to link the 6-way plug to the decoder. Only 4 pins were originally used, but for the QSI I added onto this connector the red/black speaker cable that comes with the decoder.

 

[ntpntpntp]

Here's the QSI wired in, including the speaker (to the new 6-way connector) and the chuff sensor (the latter spliced to the two blue wires top right of the picture). I had to guess that the blue wires were the chuff sensor, there seems to be no mention of these on the Bachmann diagrams? The reed switch isn't plugged in yet in the photo below.

You cannot see all the wires for the screw terminals, but order left to right in the view they are:
Black (track -)
Grey (motor -)
Yellow (rear light)
Blue (common +)
(empty) (ground)
White (front light)
Orange (motor +)
Red (track +)

 

[ntpntpntp]

Now..., the fun part with this installation is squeezing the QSI decoder and the existing main board both into the limited space in the bunker! The Magnum adapter board seems to add much more height to the assembly than is really necessary.

At first I thought I'd have to consider making some "adjustments" to the Magnum adapter board or possibly even making up my own screw terminal adapter.

However, after trimming as much as possible from the soldered pins on the underside of the adapter board, and with a little easing of the nest of wiring, I found it was actually possible to remove the main board mounting plate (three screws), site the QSI upside down and replace the main board plate on top. It's a tight fit! One of the biggest restrictions to placement is the short length of the track and motor wires coming from the main board.

Note the volume control reed switch hot-glued to the floor on the engineer's side.

 

[ntpntpntp]

Test everything (all worked fine first time!), tuck the nest of wiring into place as best you can, refit the bunker shell - being careful not to pinch any stray wires - and all done!

It's flippin' loud! I've not run it outdoors yet, but indoors 20% volume is plenty on the test rollers!

Although I did try running with the chuff sensor it seemed a little erratic so for now I've gone back to using the QSI's autochuff, adjusted to better match the 3 cylinder action. Lots of other settings to play with when I can get round to it!

I might have to go back in and re-position the reed switch nearer the outside as it's not respondng well to my magnet.

If the weather's ok tomorrrow, then sorry neighbours - lots of testing is in order and I'll be (or more likely my lad will be) cranking up the volume no doubt!

 

[ntpntpntp]

Yeah, have read that before. I always enjoy George's comprehensive notes.

I'd forgotten the little note he makes about erratic chuff sensor and the front truck shaft alignment. Don't remember the front truck shaft ever coming adrift on mine bt it's possible. Mind you, like George I reckon the QSI autochuff will do the job fine so I'm not that bothered.

Weather's looking promising for an outdoor test, but got chores and shopping to do first <groan>