This modification eliminates the muting you get on each tuning step. It keeps the audio on the entire time instead of blanking out with silence giving you that chuff-chuff sound. It gives the tuning controls more of an analogue feel and greatly enhances the enjoyment and usability of the DX-394.
Be advised that this mod allows all the PLL tuning noises to come through while using the radio. This is preferable to the chuff-chuff noises on each tuning step.
Look for the connector block of colour-coded wires containing the violet wire that's plugged into the main board at CN1, see wiring diagram. Unplug this block and using a small screwdriver release the connector on the violet wire, see photo. Remove it from the block and using a short piece of heat shrink tube to cover the connector and violet wire. Plug the connector block back into the main board at CN1.
the violet wire