Example 1 - Heljan O Gauge Class 35 Hymek with Zimo Sound - MX696

Kit: MX696KS; 2x Zimo Dumbo 50X15X14-2W speakers

We love hydraulics, and this big Heljan 7mm model is a beaut!

The usual approach is taken to fitting sound - remove the factory PCB to make space for the MX696KS large-scale decoder and screw-terminal adapter board. All wiring remains the same, except we have to add resistors to protect the lighting, as the removed PCB had the original resistors.

We remove all of the plugs and sockets too, as the wires will simply be screwed direct to the decoder's screw terminals.

A pair of dual Dumbo speakers are connected in series. The dual speakers in themselves are 2W at 4 ohm, so connecting in series gives 4W at 8 ohm.

Some work to do on the lighting, adding resistors, and ensuring they get connected up to the right terminals on the decoder!

Example 2 - MX699KS with YLR603010

Kit: MX699KS; YLR603010

Perhaps a slightly easier install - the MX699KS is a bigger shape to fit in the centre of the Hymek (at least the newer version), and a YLR603010 speaker simply slots underneath the decoder (not in the fuel tank).

Just checking the sizes and positions for the speaker and decoder here...

YLR60301 speaker goes face down under the decoder platform

MX699KS measured up in place, then wired in

Example 3: MS950

Kit: MS950; LOK950PL adapter board; YLR603010 speaker

This example is of a recent edition Hymek model (smaller flywheels) and we've gone with the latest MS950 sound decoder, which is compact (for a large scale sound decoder), and has a huge stay-alive on board.

Our YLR603010 speaker fits neatly underneath the decoder platform in the centre.

We transfer the model's wiring across from the original Heljan screw-in board to the Zimo LOK950PL adapter plate, separating the lighting so that front/rear can all be controlled separately.

Probably unnecessary. as the model appears to have protective resistors alongside the LEDs, but as a precaution we use a LAIS resistor board anyway.

The MS950 decoder then just plugs into the LOK950PL adapater plate.

Please note that these guides are provided as useful resources for you, as-is. YouChoos cannot be held responsible for errors in the information, or for any damage caused to your models or equipment if you choose to follow any of the steps detailed here.