ICR7000.3 R7000 Scan Circuits The scan rate of the R7000 is determined, in part, by a simple clock outside the microprocessor. The front panel SCAN SPEED rheostat and resistor R18 (and other components in the LOGIC UNIT) control the speed of this clock. The clock output is connected to what appears to be an input port on the microprocessor. The upshot is that we can affect the scan rate without affecting the other chores performed by the microprocessor. The modification consists simply of soldering a 470,000 ohm resistor across the leads of resistor R18 on the LOGIC UNIT circuit board. How was the value of 470,000 ohms chosen? Experimenta- tion with different resistor values showed that for values both above and below 470,000 ohms, the R7000 scan rate decreases. Not having the R7000 Service Manual, I assume this can be explained by the firmware within the microprocessor associated with the scan rate input port.1 Adding the 470,000 ohm resistor in parallel with R18, rather than just replacing R18, has a few advantages: 1. The modification is easily undone, returning the radio to stock condition. 2. The LOGIC UNIT board does not have to be removed, as would be the case if R18 was unsoldered from the foil side. CONTINUED IN FILE ICR7000.1 - REQUEST FROM SERVER