Kit: Zimo MX649 with Minnow4 Speaker and SACC16 kit with 2x 330uF Tantalums for stay-alive
Pretty little B4 model from Dapol. Careful as you take it apart though as everything disassembles and drops out! Once you've
removed the screws for the keeper plate and dropped the chassis out, screw the keeper plate back in to save the mechanism from
dropping out while you are working and testing.
This is our first attempt at a B4, so fairly conservative with the little Minnow4 speaker, and perhaps not the best placement
of the stay-alive (see later example for improvement).
Neat PCB with 6pin socket provided, but no good for sound. Model also provides 2 LEDs for firebox light which is a nice bonus -
we'll reuse those with the DCC Sound installation.
A little extra room to play with in the nose, but not much, so some careful planning required.
No extra space at the rear to speak of.
Here's the kit we will attempt - MX649 (hard-wired of course), Minnow4 speaker and stay-alive using SACC16 board and a 330uF
Tantalum (flat one):
Snip off the original PCB supports to give us more flush space for the decoder...
Looking at the profile, I reckon we can actually fit a pair of 330uF Tantalums (flat versions) to the SACC16 board to double
the stay-alive... let's give it a go...
Hard-wire the motor and pickups, then join in the firebox lighting. Note everything is directly wired to the decoder so no wire
joins as this would take up too much space. We split off BLUE (common positive) from the SACC16 input, via a resistor to the
positive pad on the B4's firebox lighting PCB. The 2 LEDs are controlled by AUX3/FA1 and AUX4/FA2 outputs on the decoder so we
can control them independently.
Now test, and a case of getting everything neat and balanced so that it does not interfere with the motor or fly-wheel.
Minnow4 speaker fits in the top of the nose, secured with some Black Tack - don't want that falling down!
Some squishing and squeezing to get it back together, but done, and runs sweet! Our sound project is a variant of the Andrew
Barclay project with modified whistles to suit the B4.
Our second attempt at a B4, we improve on the speaker, using a SugarCurve7 instead, which is notably louder than the Minnow. We
also move the location of the stay-alive kit, with the speaker, up into the nose.
Here is the kit before we start...
Prove that the SugarCurve7 will fit, and body still fit afterwards!
Here is our stay-alive, comprising SACC16 PCB and a pair of flat/wide 330uF Tantalums. We cut the last perforated part of the
SACC16 board away, as this makes it longer than it needs to be for the pair of capacitors.
The MX649 has its heat shrink sleeve removed, and we remove the unwanted function outputs wires (white and yellow are not
required as we don't have directional lights). We carefully wire the motor and pickups in, and the pair of firebox LEDs,
including a protective resistor which is shared between both LEDs. We have to snip the little PCB mounts that there in the
model so that the decoder sits lower.
Next we assemble the stay-alive, soldering a tantalum on the top, and another on the bottom, making them as flat as possible.
Double-check that the speaker and stay-alive will fit OK in the boiler.
It will go, but looks quite tight on the end of the motor shaft, so we chop the very end of that off carefully so that it won't
foul on the new components in the boiler.
Connect up the speaker and stay-alive using relatively short wires - short enough that they don't take up too much space, but
long enough that we can handle the whole thing as we put everything into position.
With the speaker and stay-alive protected with Kapton tape, secure them in the boiler with a little Black Tack. The curve of
the speaker should sit against the curved boiler top, and the stay-alive below it.
Finally, all back together for a test run and a photo shoot!