This mod involves the subreceiver of the FT1000D device in CW mode.
When in the sub-receiver the optional CW filter is absent, the sub receiver only receive in CW wide mode, using the SSB filter. But, if in the main receiver the filter selected is the 500Hz or the 250Hz, pressing the A>B button to transfer data to sub receiver causes the sub receiver is mute because the optional filter is selected, but is absent.
This mod select the SSB filter in the sub-receiver regardless the filter selected in the main receiver, in CW mode.
Open both covers of the FT1000D and locate the connector marked J6007, near the screw in the bottom part of the board. Note the violet wire in position n.1. Cut this wire, and also the white wire in position n.3, about 1cm away from the connector.
Solder the anode of 1 diode 1N4148 at the violet wire, (not the part of the wire attached to the connector, the other).
Do the same (use another diode) with the white wire.
Connect both cathodes to the pin 3 of the connector (solder the diodes to the 1cm length of wire remaining in the connector).
Insulate all with tape and this is all.
Note that the 1cm violet wire attached to the connector remain unconnected.
NOTE: IF you, in future, install the optional filter, obviously you must remove this mod and put all as before.
NOTE: to make this mod, may be someone think to connect one diode between L6006 and L6005: this system dont work fine, i tried and exclude this possibility.