Zimo MX648, SugarCube and tantalum stay-alive install in a Dapol Class 35 Hymek N Gauge diesel pair...
Fitting DCC sound into the powered engine is not feasible using a Zimo decoder, so we opt for placing it in a dummy engine
instead, which already has pickups and factory directional lighting, so half the job is already done!
We plan to add a Zimo MX648 sound decoder, SugarCube speaker and full stay-alive circuit (SPIEKOMP) to allow us to attach some
tiny tantalum capacitors. The stay-alive is essential in this model because there is very little body weight - even the chassis
is plastic instead of metal.
Below you can see the components, including 3 of these tantalums (220uF/16V) joined in parallel.
The hollow interior is not big enough for all of these components, even with the enclosure of the SugarCube reduced to just a
few mm, so we must hollow it out a bit more with our trusty Dremel. A gentle and secure touch is essential!
Keep test fitting the components and hollowing out a little more until you are happy with the fit, and then give it a little
more space on top - room to breathe!
You will also have to allow some width for the decoder to sit slightly below the surface - so that the larger components of the
decoder fit into the hollow just a fraction - this is essential, or the body won't go back on flush later.
Next we assemble the SPIEKOMP ciruit (details not given here), insulate it and squash it down into the remaining part of the
hollow in the chassis. We attach the SPIEKOMP wiring to the tantalums at one end, and the decoder GND annd +VE on the other
end. Red and black decoder wires should also be connected to the pickups now.
Put everything neatly together, and hard-wire the model's lighting boards via resistors to the decoder (details not given
here), and you're almost done!
In fact, our final shot here shows the results with both the powered and dummy engines together, but also with independently
controlled cab lights and drivers installed in each.