I am repairing a TS790 for a friend with the following problem: Main RX, 432 band, RX approx 60 dB low. Sub RX OK. It appears that the MRBK signal is logic 0 and apparently should be 1....= .this comes from the Control unit, I do not have complete schematics at t= his time for the radio...will anyone please help me a bit here? Thanks in advance John, N6AX