SB-904 TM-2550 DCL Call Sign Data 2-7-86 Some owners of the TM-2530/50/70 have reported a loss of the DCL system call sign data when the power switch is turned off. The call sign data actually remains in memory, but timing prevents its utilization in some radios. Adding a resistor will correct this problem. If you receive a radio that exhibits this symptom add a 47K ohm resistor to IC3 to the Slave CPU on the control unit (X53-1440-XX) between pins 4 and 20. Cover the resistor leads with "spaghetti" type insulation. Adding the resistor to radios that do not have this symptom will not cause any problems, so you may wish to add the resistor if you receive a radio for service for some other problem. Before soldering unplug the DC power cable and antenna from the radio. When soldering to this IC you must use a soldering iron that provides voltage isolation on the tip since IC3 is a CMOS device and can be easily damaged by static electricity or voltage on your iron. Use normal CMOS precautions. One final precaution: Don't bridge any of the pins on the IC with excess solder! Time required for this modification is 1/2 hour or less. (c) 121589TKC