[rfeenstra]

Re-check your 123A.  It appears that you have it wired with the negative tied to ground.  The positive must be tied to Chassis ground and the negative to the negative terminals of 120, 121, and 123.  This junction typically rides at about  NEGATIVE 25 to 50 volts  DC referenced to chassis ground.  This negative voltage will vary depending on the model of the radio. A 50 volt cap is usually sufficient. I will typically, though, use a higher voltage cap just because I have them. If 123A is wired backwards, it probably will fail as you described.