After making a careful mobile installation, a friend of mine found his TS450S to have
intermittent receive. He removed the screw that was going through the coax in
his car and made a second installation in his truck. More intermittent. With
some careful diagnosis he found that moving the coax connector up and down
caused the change in signal. With the radio opened up, I found that moving the
coax connector was breaking the contact between the wire from the center
conductor and the board (W1 in the schematic). To save on pulling the filter
board, I used a short piece of very flexible test prod wire to connect from
the center of the UHF connector to W6 on the top of the PC board. W6 jumps
over the contacts of a relay used only in the TS-690S. For added security, I
also added another wire of the same material from the ground lug on the UHF
connector to the end of D11 away from the coax connector. So now if the
flexible back panel breaks the other wire too, it won't have so much effect.
The coax connector is mounted on a 1/32" plated steel panel so is excessively
flexible in mounting. Ideally that connector should be mounted far more
stiffly for those that use real RG-8 coax.